summaryrefslogtreecommitdiff
path: root/src/static_libs/rg_etc/rg_etc1.cpp
blob: a1cd73f54636238f8a9592a5476b69ba40b272a0 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
1183
1184
1185
1186
1187
1188
1189
1190
1191
1192
1193
1194
1195
1196
1197
1198
1199
1200
1201
1202
1203
1204
1205
1206
1207
1208
1209
1210
1211
1212
1213
1214
1215
1216
1217
1218
1219
1220
1221
1222
1223
1224
1225
1226
1227
1228
1229
1230
1231
1232
1233
1234
1235
1236
1237
1238
1239
1240
1241
1242
1243
1244
1245
1246
1247
1248
1249
1250
1251
1252
1253
1254
1255
1256
1257
1258
1259
1260
1261
1262
1263
1264
1265
1266
1267
1268
1269
1270
1271
1272
1273
1274
1275
1276
1277
1278
1279
1280
1281
1282
1283
1284
1285
1286
1287
1288
1289
1290
1291
1292
1293
1294
1295
1296
1297
1298
1299
1300
1301
1302
1303
1304
1305
1306
1307
1308
1309
1310
1311
1312
1313
1314
1315
1316
1317
1318
1319
1320
1321
1322
1323
1324
1325
1326
1327
1328
1329
1330
1331
1332
1333
1334
1335
1336
1337
1338
1339
1340
1341
1342
1343
1344
1345
1346
1347
1348
1349
1350
1351
1352
1353
1354
1355
1356
1357
1358
1359
1360
1361
1362
1363
1364
1365
1366
1367
1368
1369
1370
1371
1372
1373
1374
1375
1376
1377
1378
1379
1380
1381
1382
1383
1384
1385
1386
1387
1388
1389
1390
1391
1392
1393
1394
1395
1396
1397
1398
1399
1400
1401
1402
1403
1404
1405
1406
1407
1408
1409
1410
1411
1412
1413
1414
1415
1416
1417
1418
1419
1420
1421
1422
1423
1424
1425
1426
1427
1428
1429
1430
1431
1432
1433
1434
1435
1436
1437
1438
1439
1440
1441
1442
1443
1444
1445
1446
1447
1448
1449
1450
1451
1452
1453
1454
1455
1456
1457
1458
1459
1460
1461
1462
1463
1464
1465
1466
1467
1468
1469
1470
1471
1472
1473
1474
1475
1476
1477
1478
1479
1480
1481
1482
1483
1484
1485
1486
1487
1488
1489
1490
1491
1492
1493
1494
1495
1496
1497
1498
1499
1500
1501
1502
1503
1504
1505
1506
1507
1508
1509
1510
1511
1512
1513
1514
1515
1516
1517
1518
1519
1520
1521
1522
1523
1524
1525
1526
1527
1528
1529
1530
1531
1532
1533
1534
1535
1536
1537
1538
1539
1540
1541
1542
1543
1544
1545
1546
1547
1548
1549
1550
1551
1552
1553
1554
1555
1556
1557
1558
1559
1560
1561
1562
1563
1564
1565
1566
1567
1568
1569
1570
1571
1572
1573
1574
1575
1576
1577
1578
1579
1580
1581
1582
1583
1584
1585
1586
1587
1588
1589
1590
1591
1592
1593
1594
1595
1596
1597
1598
1599
1600
1601
1602
1603
1604
1605
1606
1607
1608
1609
1610
1611
1612
1613
1614
1615
1616
1617
1618
1619
1620
1621
1622
1623
1624
1625
1626
1627
1628
1629
1630
1631
1632
1633
1634
1635
1636
1637
1638
1639
1640
1641
1642
1643
1644
1645
1646
1647
1648
1649
1650
1651
1652
1653
1654
1655
1656
1657
1658
1659
1660
1661
1662
1663
1664
1665
1666
1667
1668
1669
1670
1671
1672
1673
1674
1675
1676
1677
1678
1679
1680
1681
1682
1683
1684
1685
1686
1687
1688
1689
1690
1691
1692
1693
1694
1695
1696
1697
1698
1699
1700
1701
1702
1703
1704
1705
1706
1707
1708
1709
1710
1711
1712
1713
1714
1715
1716
1717
1718
1719
1720
1721
1722
1723
1724
1725
1726
1727
1728
1729
1730
1731
1732
1733
1734
1735
1736
1737
1738
1739
1740
1741
1742
1743
1744
1745
1746
1747
1748
1749
1750
1751
1752
1753
1754
1755
1756
1757
1758
1759
1760
1761
1762
1763
1764
1765
1766
1767
1768
1769
1770
1771
1772
1773
1774
1775
1776
1777
1778
1779
1780
1781
1782
1783
1784
1785
1786
1787
1788
1789
1790
1791
1792
1793
1794
1795
1796
1797
1798
1799
1800
1801
1802
1803
1804
1805
1806
1807
1808
1809
1810
1811
1812
1813
1814
1815
1816
1817
1818
1819
1820
1821
1822
1823
1824
1825
1826
1827
1828
1829
1830
1831
1832
1833
1834
1835
1836
1837
1838
1839
1840
1841
1842
1843
1844
1845
1846
1847
1848
1849
1850
1851
1852
1853
1854
1855
1856
1857
1858
1859
1860
1861
1862
1863
1864
1865
1866
1867
1868
1869
1870
1871
1872
1873
1874
1875
1876
1877
1878
1879
1880
1881
1882
1883
1884
1885
1886
1887
1888
1889
1890
1891
1892
1893
1894
1895
1896
1897
1898
1899
1900
1901
1902
1903
1904
1905
1906
1907
1908
1909
1910
1911
1912
1913
1914
1915
1916
1917
1918
1919
1920
1921
1922
1923
1924
1925
1926
1927
1928
1929
1930
1931
1932
1933
1934
1935
1936
1937
1938
1939
1940
1941
1942
1943
1944
1945
1946
1947
1948
1949
1950
1951
1952
1953
1954
1955
1956
1957
1958
1959
1960
1961
1962
1963
1964
1965
1966
1967
1968
1969
1970
1971
1972
1973
1974
1975
1976
1977
1978
1979
1980
1981
1982
1983
1984
1985
1986
1987
1988
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
2011
2012
2013
2014
2015
2016
2017
2018
2019
2020
2021
2022
2023
2024
2025
2026
2027
2028
2029
2030
2031
2032
2033
2034
2035
2036
2037
2038
2039
2040
2041
2042
2043
2044
2045
2046
2047
2048
2049
2050
2051
2052
2053
2054
2055
2056
2057
2058
2059
2060
2061
2062
2063
2064
2065
2066
2067
2068
2069
2070
2071
2072
2073
2074
2075
2076
2077
2078
2079
2080
2081
2082
2083
2084
2085
2086
2087
2088
2089
2090
2091
2092
2093
2094
2095
2096
2097
2098
2099
2100
2101
2102
2103
2104
2105
2106
2107
2108
2109
2110
2111
2112
2113
2114
2115
2116
2117
2118
2119
2120
2121
2122
2123
2124
2125
2126
2127
2128
2129
2130
2131
2132
2133
2134
2135
2136
2137
2138
2139
2140
2141
2142
2143
2144
2145
2146
2147
2148
2149
2150
2151
2152
2153
2154
2155
2156
2157
2158
2159
2160
2161
2162
2163
2164
2165
2166
2167
2168
2169
2170
2171
2172
2173
2174
2175
2176
2177
2178
2179
2180
2181
2182
2183
2184
2185
2186
2187
2188
2189
2190
2191
2192
2193
2194
2195
2196
2197
2198
2199
2200
2201
2202
2203
2204
2205
2206
2207
2208
2209
2210
2211
2212
2213
2214
2215
2216
2217
2218
2219
2220
2221
2222
2223
2224
2225
2226
2227
2228
2229
2230
2231
2232
2233
2234
2235
2236
2237
2238
2239
2240
2241
2242
2243
2244
2245
2246
2247
2248
2249
2250
2251
2252
2253
2254
2255
2256
2257
2258
2259
2260
2261
2262
2263
2264
2265
2266
2267
2268
2269
2270
2271
2272
2273
2274
2275
2276
2277
2278
2279
2280
2281
2282
2283
2284
2285
2286
2287
2288
2289
2290
2291
2292
2293
2294
2295
2296
2297
2298
2299
2300
2301
2302
2303
2304
2305
2306
2307
2308
2309
2310
2311
2312
2313
2314
2315
2316
2317
2318
2319
2320
2321
2322
2323
2324
2325
2326
2327
2328
2329
2330
2331
2332
2333
2334
2335
2336
2337
2338
2339
2340
2341
2342
2343
2344
2345
2346
2347
2348
2349
2350
2351
2352
2353
2354
2355
2356
2357
2358
2359
2360
2361
2362
2363
2364
2365
2366
2367
2368
2369
2370
2371
2372
2373
2374
2375
2376
2377
2378
2379
2380
2381
2382
2383
2384
2385
2386
2387
2388
2389
2390
2391
2392
2393
2394
2395
2396
2397
2398
2399
2400
2401
2402
2403
2404
2405
2406
2407
2408
2409
2410
2411
2412
2413
2414
2415
2416
2417
2418
2419
2420
2421
2422
2423
2424
2425
2426
2427
2428
2429
2430
2431
2432
2433
2434
2435
2436
2437
2438
2439
2440
2441
2442
2443
2444
2445
2446
// File: rg_etc1.cpp - Fast, high quality ETC1 block packer/unpacker - Rich Geldreich <richgel99@gmail.com>
// Please see ZLIB license at the end of rg_etc1.h.
//
// For more information Ericsson Texture Compression (ETC/ETC1), see:
// http://www.khronos.org/registry/gles/extensions/OES/OES_compressed_ETC1_RGB8_texture.txt
//
// v1.04 - 5/15/14 - Fix signed vs. unsigned subtraction problem (noticed when compiled with gcc) in pack_etc1_block_init(). 
//         This issue would cause an assert when this func. was called in debug. (Note this module was developed/testing with MSVC, 
//         I still need to test it throughly when compiled with gcc.)
//
// v1.03 - 5/12/13 - Initial public release
#include "rg_etc1.h"

#include <stdlib.h>
#include <memory.h>
#include <assert.h>
//#include <stdio.h>
#include <math.h>

#pragma warning (disable: 4201) //  nonstandard extension used : nameless struct/union

#if defined(_DEBUG) || defined(DEBUG)
#define RG_ETC1_BUILD_DEBUG
#endif

#define RG_ETC1_ASSERT assert

namespace rg_etc1
{
   typedef unsigned char uint8;
   typedef unsigned short uint16;
   typedef unsigned int uint;
   typedef unsigned int uint32;
   typedef long long int64;
   typedef unsigned long long uint64;

   const uint32 cUINT32_MAX = 0xFFFFFFFFU;
   const uint64 cUINT64_MAX = 0xFFFFFFFFFFFFFFFFULL; //0xFFFFFFFFFFFFFFFFui64;
   
   template<typename T> inline T minimum(T a, T b) { return (a < b) ? a : b; }
   template<typename T> inline T minimum(T a, T b, T c) { return minimum(minimum(a, b), c); }
   template<typename T> inline T maximum(T a, T b) { return (a > b) ? a : b; }
   template<typename T> inline T maximum(T a, T b, T c) { return maximum(maximum(a, b), c); }
   template<typename T> inline T clamp(T value, T low, T high) { return (value < low) ? low : ((value > high) ? high : value); }
   template<typename T> inline T square(T value) { return value * value; }
   template<typename T> inline void zero_object(T& obj) { memset((void*)&obj, 0, sizeof(obj)); }
   template<typename T> inline void zero_this(T* pObj) { memset((void*)pObj, 0, sizeof(*pObj)); }

   template<class T, size_t N> T decay_array_to_subtype(T (&a)[N]);   

#define RG_ETC1_ARRAY_SIZE(X) (sizeof(X) / sizeof(decay_array_to_subtype(X)))

   enum eNoClamp { cNoClamp };

   struct color_quad_u8
   {
      static inline int clamp(int v) { if (v & 0xFFFFFF00U) v = (~(static_cast<int>(v) >> 31)) & 0xFF; return v; }

      struct component_traits { enum { cSigned = false, cFloat = false, cMin = 0U, cMax = 255U }; };

   public:
      typedef unsigned char component_t;
      typedef int parameter_t;

      enum { cNumComps = 4 };

      union
      {
         struct
         {
            component_t r;
            component_t g;
            component_t b;
            component_t a;
         };

         component_t c[cNumComps];

         uint32 m_u32;
      };

      inline color_quad_u8()
      {
      }

      inline color_quad_u8(const color_quad_u8& other) : m_u32(other.m_u32)
      {
      }

      explicit inline color_quad_u8(parameter_t y, parameter_t alpha = component_traits::cMax)
      {
         set(y, alpha);
      }

      inline color_quad_u8(parameter_t red, parameter_t green, parameter_t blue, parameter_t alpha = component_traits::cMax)
      {
         set(red, green, blue, alpha);
      }

      explicit inline color_quad_u8(eNoClamp, parameter_t y, parameter_t alpha = component_traits::cMax)
      {
         set_noclamp_y_alpha(y, alpha);
      }

      inline color_quad_u8(eNoClamp, parameter_t red, parameter_t green, parameter_t blue, parameter_t alpha = component_traits::cMax)
      {
         set_noclamp_rgba(red, green, blue, alpha);
      }

      inline void clear()
      {
         m_u32 = 0;
      }

      inline color_quad_u8& operator= (const color_quad_u8& other)
      {
         m_u32 = other.m_u32;
         return *this;
      }

      inline color_quad_u8& set_rgb(const color_quad_u8& other)
      {
         r = other.r;
         g = other.g;
         b = other.b;
         return *this;
      }

      inline color_quad_u8& operator= (parameter_t y)
      {
         set(y, component_traits::cMax);
         return *this;
      }

      inline color_quad_u8& set(parameter_t y, parameter_t alpha = component_traits::cMax)
      {
         y = clamp(y);
         alpha = clamp(alpha);
         r = static_cast<component_t>(y);
         g = static_cast<component_t>(y);
         b = static_cast<component_t>(y);
         a = static_cast<component_t>(alpha);
         return *this;
      }

      inline color_quad_u8& set_noclamp_y_alpha(parameter_t y, parameter_t alpha = component_traits::cMax)
      {
         RG_ETC1_ASSERT( (y >= component_traits::cMin) && (y <= component_traits::cMax) );
         RG_ETC1_ASSERT( (alpha >= component_traits::cMin) && (alpha <= component_traits::cMax) );

         r = static_cast<component_t>(y);
         g = static_cast<component_t>(y);
         b = static_cast<component_t>(y);
         a = static_cast<component_t>(alpha);
         return *this;
      }

      inline color_quad_u8& set(parameter_t red, parameter_t green, parameter_t blue, parameter_t alpha = component_traits::cMax)
      {
         r = static_cast<component_t>(clamp(red));
         g = static_cast<component_t>(clamp(green));
         b = static_cast<component_t>(clamp(blue));
         a = static_cast<component_t>(clamp(alpha));
         return *this;
      }

      inline color_quad_u8& set_noclamp_rgba(parameter_t red, parameter_t green, parameter_t blue, parameter_t alpha)
      {
         RG_ETC1_ASSERT( (red >= component_traits::cMin) && (red <= component_traits::cMax) );
         RG_ETC1_ASSERT( (green >= component_traits::cMin) && (green <= component_traits::cMax) );
         RG_ETC1_ASSERT( (blue >= component_traits::cMin) && (blue <= component_traits::cMax) );
         RG_ETC1_ASSERT( (alpha >= component_traits::cMin) && (alpha <= component_traits::cMax) );

         r = static_cast<component_t>(red);
         g = static_cast<component_t>(green);
         b = static_cast<component_t>(blue);
         a = static_cast<component_t>(alpha);
         return *this;
      }

      inline color_quad_u8& set_noclamp_rgb(parameter_t red, parameter_t green, parameter_t blue)
      {
         RG_ETC1_ASSERT( (red >= component_traits::cMin) && (red <= component_traits::cMax) );
         RG_ETC1_ASSERT( (green >= component_traits::cMin) && (green <= component_traits::cMax) );
         RG_ETC1_ASSERT( (blue >= component_traits::cMin) && (blue <= component_traits::cMax) );

         r = static_cast<component_t>(red);
         g = static_cast<component_t>(green);
         b = static_cast<component_t>(blue);
         return *this;
      }

      static inline parameter_t get_min_comp() { return component_traits::cMin; }
      static inline parameter_t get_max_comp() { return component_traits::cMax; }
      static inline bool get_comps_are_signed() { return component_traits::cSigned; }

      inline component_t operator[] (uint i) const { RG_ETC1_ASSERT(i < cNumComps); return c[i]; }
      inline component_t& operator[] (uint i) { RG_ETC1_ASSERT(i < cNumComps); return c[i]; }

      inline color_quad_u8& set_component(uint i, parameter_t f)
      {
         RG_ETC1_ASSERT(i < cNumComps);

         c[i] = static_cast<component_t>(clamp(f));

         return *this;
      }

      inline color_quad_u8& set_grayscale(parameter_t l)
      {
         component_t x = static_cast<component_t>(clamp(l));
         c[0] = x;
         c[1] = x;
         c[2] = x;
         return *this;
      }

      inline color_quad_u8& clamp(const color_quad_u8& l, const color_quad_u8& h)
      {
         for (uint i = 0; i < cNumComps; i++)
            c[i] = static_cast<component_t>(rg_etc1::clamp<parameter_t>(c[i], l[i], h[i]));
         return *this;
      }

      inline color_quad_u8& clamp(parameter_t l, parameter_t h)
      {
         for (uint i = 0; i < cNumComps; i++)
            c[i] = static_cast<component_t>(rg_etc1::clamp<parameter_t>(c[i], l, h));
         return *this;
      }

      // Returns CCIR 601 luma (consistent with color_utils::RGB_To_Y).
      inline parameter_t get_luma() const
      {
         return static_cast<parameter_t>((19595U * r + 38470U * g + 7471U * b + 32768U) >> 16U);
      }

      // Returns REC 709 luma.
      inline parameter_t get_luma_rec709() const
      {
         return static_cast<parameter_t>((13938U * r + 46869U * g + 4729U * b + 32768U) >> 16U);
      }

      inline uint squared_distance_rgb(const color_quad_u8& c) const
      {
         return rg_etc1::square(r - c.r) + rg_etc1::square(g - c.g) + rg_etc1::square(b - c.b);
      }

      inline uint squared_distance_rgba(const color_quad_u8& c) const
      {
         return rg_etc1::square(r - c.r) + rg_etc1::square(g - c.g) + rg_etc1::square(b - c.b) + rg_etc1::square(a - c.a);
      }

      inline bool rgb_equals(const color_quad_u8& rhs) const
      {
         return (r == rhs.r) && (g == rhs.g) && (b == rhs.b);
      }

      inline bool operator== (const color_quad_u8& rhs) const
      {
         return m_u32 == rhs.m_u32;
      }

      color_quad_u8& operator+= (const color_quad_u8& other)
      {
         for (uint i = 0; i < 4; i++)
            c[i] = static_cast<component_t>(clamp(c[i] + other.c[i]));
         return *this;
      }

      color_quad_u8& operator-= (const color_quad_u8& other)
      {
         for (uint i = 0; i < 4; i++)
            c[i] = static_cast<component_t>(clamp(c[i] - other.c[i]));
         return *this;
      }

      friend color_quad_u8 operator+ (const color_quad_u8& lhs, const color_quad_u8& rhs)
      {
         color_quad_u8 result(lhs);
         result += rhs;
         return result;
      }

      friend color_quad_u8 operator- (const color_quad_u8& lhs, const color_quad_u8& rhs)
      {
         color_quad_u8 result(lhs);
         result -= rhs;
         return result;
      }
   }; // class color_quad_u8

   struct vec3F
   {
      float m_s[3];
      
      inline vec3F() { }
      inline vec3F(float s) { m_s[0] = s; m_s[1] = s; m_s[2] = s; }
      inline vec3F(float x, float y, float z) { m_s[0] = x; m_s[1] = y; m_s[2] = z; }
      
      inline float operator[] (uint i) const { RG_ETC1_ASSERT(i < 3); return m_s[i]; }

      inline vec3F& operator += (const vec3F& other) { for (uint i = 0; i < 3; i++) m_s[i] += other.m_s[i]; return *this; }

      inline vec3F& operator *= (float s) { for (uint i = 0; i < 3; i++) m_s[i] *= s; return *this; }
   };
     
   enum etc_constants
   {
      cETC1BytesPerBlock = 8U,

      cETC1SelectorBits = 2U,
      cETC1SelectorValues = 1U << cETC1SelectorBits,
      cETC1SelectorMask = cETC1SelectorValues - 1U,

      cETC1BlockShift = 2U,
      cETC1BlockSize = 1U << cETC1BlockShift,

      cETC1LSBSelectorIndicesBitOffset = 0,
      cETC1MSBSelectorIndicesBitOffset = 16,

      cETC1FlipBitOffset = 32,
      cETC1DiffBitOffset = 33,

      cETC1IntenModifierNumBits = 3,
      cETC1IntenModifierValues = 1 << cETC1IntenModifierNumBits,
      cETC1RightIntenModifierTableBitOffset = 34,
      cETC1LeftIntenModifierTableBitOffset = 37,

      // Base+Delta encoding (5 bit bases, 3 bit delta)
      cETC1BaseColorCompNumBits = 5,
      cETC1BaseColorCompMax = 1 << cETC1BaseColorCompNumBits,

      cETC1DeltaColorCompNumBits = 3,
      cETC1DeltaColorComp = 1 << cETC1DeltaColorCompNumBits,
      cETC1DeltaColorCompMax = 1 << cETC1DeltaColorCompNumBits,

      cETC1BaseColor5RBitOffset = 59,
      cETC1BaseColor5GBitOffset = 51,
      cETC1BaseColor5BBitOffset = 43,

      cETC1DeltaColor3RBitOffset = 56,
      cETC1DeltaColor3GBitOffset = 48,
      cETC1DeltaColor3BBitOffset = 40,

      // Absolute (non-delta) encoding (two 4-bit per component bases)
      cETC1AbsColorCompNumBits = 4,
      cETC1AbsColorCompMax = 1 << cETC1AbsColorCompNumBits,

      cETC1AbsColor4R1BitOffset = 60,
      cETC1AbsColor4G1BitOffset = 52,
      cETC1AbsColor4B1BitOffset = 44,

      cETC1AbsColor4R2BitOffset = 56,
      cETC1AbsColor4G2BitOffset = 48,
      cETC1AbsColor4B2BitOffset = 40,

      cETC1ColorDeltaMin = -4,
      cETC1ColorDeltaMax = 3,

      // Delta3:
      // 0   1   2   3   4   5   6   7
      // 000 001 010 011 100 101 110 111
      // 0   1   2   3   -4  -3  -2  -1
   };
   
   static uint8 g_quant5_tab[256+16];

   static const int g_etc1_inten_tables[cETC1IntenModifierValues][cETC1SelectorValues] = 
   { 
      { -8,  -2,   2,   8 }, { -17,  -5,  5,  17 }, { -29,  -9,   9,  29 }, {  -42, -13, 13,  42 }, 
      { -60, -18, 18,  60 }, { -80, -24, 24,  80 }, { -106, -33, 33, 106 }, { -183, -47, 47, 183 } 
   };

   static const uint8 g_etc1_to_selector_index[cETC1SelectorValues] = { 2, 3, 1, 0 };
   static const uint8 g_selector_index_to_etc1[cETC1SelectorValues] = { 3, 2, 0, 1 };
      
   // Given an ETC1 diff/inten_table/selector, and an 8-bit desired color, this table encodes the best packed_color in the low byte, and the abs error in the high byte.
   static uint16 g_etc1_inverse_lookup[2*8*4][256];      // [diff/inten_table/selector][desired_color]

   // g_color8_to_etc_block_config[color][table_index] = Supplies for each 8-bit color value a list of packed ETC1 diff/intensity table/selectors/packed_colors that map to that color.
   // To pack: diff | (inten << 1) | (selector << 4) | (packed_c << 8)
   static const uint16 g_color8_to_etc_block_config_0_255[2][33] =
   {
      { 0x0000,  0x0010,  0x0002,  0x0012,  0x0004,  0x0014,  0x0006,  0x0016,  0x0008,  0x0018,  0x000A,  0x001A,  0x000C,  0x001C,  0x000E,  0x001E,
        0x0001,  0x0011,  0x0003,  0x0013,  0x0005,  0x0015,  0x0007,  0x0017,  0x0009,  0x0019,  0x000B,  0x001B,  0x000D,  0x001D,  0x000F,  0x001F, 0xFFFF },
      { 0x0F20,  0x0F30,  0x0E32,  0x0F22,  0x0E34,  0x0F24,  0x0D36,  0x0F26,  0x0C38,  0x0E28,  0x0B3A,  0x0E2A,  0x093C,  0x0E2C,  0x053E,  0x0D2E,
        0x1E31,  0x1F21,  0x1D33,  0x1F23,  0x1C35,  0x1E25,  0x1A37,  0x1E27,  0x1839,  0x1D29,  0x163B,  0x1C2B,  0x133D,  0x1B2D,  0x093F,  0x1A2F, 0xFFFF },
   };

   // Really only [254][11].
   static const uint16 g_color8_to_etc_block_config_1_to_254[254][12] = 
   {
      { 0x021C, 0x0D0D, 0xFFFF }, { 0x0020, 0x0021, 0x0A0B, 0x061F, 0xFFFF }, { 0x0113, 0x0217, 0xFFFF }, { 0x0116, 0x031E,
      0x0B0E, 0x0405, 0xFFFF }, { 0x0022, 0x0204, 0x050A, 0x0023, 0xFFFF }, { 0x0111, 0x0319, 0x0809, 0x170F, 0xFFFF }, {
      0x0303, 0x0215, 0x0607, 0xFFFF }, { 0x0030, 0x0114, 0x0408, 0x0031, 0x0201, 0x051D, 0xFFFF }, { 0x0100, 0x0024, 0x0306,
      0x0025, 0x041B, 0x0E0D, 0xFFFF }, { 0x021A, 0x0121, 0x0B0B, 0x071F, 0xFFFF }, { 0x0213, 0x0317, 0xFFFF }, { 0x0112,
      0x0505, 0xFFFF }, { 0x0026, 0x070C, 0x0123, 0x0027, 0xFFFF }, { 0x0211, 0x0909, 0xFFFF }, { 0x0110, 0x0315, 0x0707,
      0x0419, 0x180F, 0xFFFF }, { 0x0218, 0x0131, 0x0301, 0x0403, 0x061D, 0xFFFF }, { 0x0032, 0x0202, 0x0033, 0x0125, 0x051B,
      0x0F0D, 0xFFFF }, { 0x0028, 0x031C, 0x0221, 0x0029, 0xFFFF }, { 0x0120, 0x0313, 0x0C0B, 0x081F, 0xFFFF }, { 0x0605,
      0x0417, 0xFFFF }, { 0x0216, 0x041E, 0x0C0E, 0x0223, 0x0127, 0xFFFF }, { 0x0122, 0x0304, 0x060A, 0x0311, 0x0A09, 0xFFFF
      }, { 0x0519, 0x190F, 0xFFFF }, { 0x002A, 0x0231, 0x0503, 0x0415, 0x0807, 0x002B, 0x071D, 0xFFFF }, { 0x0130, 0x0214,
      0x0508, 0x0401, 0x0133, 0x0225, 0x061B, 0xFFFF }, { 0x0200, 0x0124, 0x0406, 0x0321, 0x0129, 0x100D, 0xFFFF }, { 0x031A,
      0x0D0B, 0x091F, 0xFFFF }, { 0x0413, 0x0705, 0x0517, 0xFFFF }, { 0x0212, 0x0034, 0x0323, 0x0035, 0x0227, 0xFFFF }, {
      0x0126, 0x080C, 0x0B09, 0xFFFF }, { 0x0411, 0x0619, 0x1A0F, 0xFFFF }, { 0x0210, 0x0331, 0x0603, 0x0515, 0x0907, 0x012B,
      0xFFFF }, { 0x0318, 0x002C, 0x0501, 0x0233, 0x0325, 0x071B, 0x002D, 0x081D, 0xFFFF }, { 0x0132, 0x0302, 0x0229, 0x110D,
      0xFFFF }, { 0x0128, 0x041C, 0x0421, 0x0E0B, 0x0A1F, 0xFFFF }, { 0x0220, 0x0513, 0x0617, 0xFFFF }, { 0x0135, 0x0805,
      0x0327, 0xFFFF }, { 0x0316, 0x051E, 0x0D0E, 0x0423, 0xFFFF }, { 0x0222, 0x0404, 0x070A, 0x0511, 0x0719, 0x0C09, 0x1B0F,
      0xFFFF }, { 0x0703, 0x0615, 0x0A07, 0x022B, 0xFFFF }, { 0x012A, 0x0431, 0x0601, 0x0333, 0x012D, 0x091D, 0xFFFF }, {
      0x0230, 0x0314, 0x0036, 0x0608, 0x0425, 0x0037, 0x0329, 0x081B, 0x120D, 0xFFFF }, { 0x0300, 0x0224, 0x0506, 0x0521,
      0x0F0B, 0x0B1F, 0xFFFF }, { 0x041A, 0x0613, 0x0717, 0xFFFF }, { 0x0235, 0x0905, 0xFFFF }, { 0x0312, 0x0134, 0x0523,
      0x0427, 0xFFFF }, { 0x0226, 0x090C, 0x002E, 0x0611, 0x0D09, 0x002F, 0xFFFF }, { 0x0715, 0x0B07, 0x0819, 0x032B, 0x1C0F,
      0xFFFF }, { 0x0310, 0x0531, 0x0701, 0x0803, 0x022D, 0x0A1D, 0xFFFF }, { 0x0418, 0x012C, 0x0433, 0x0525, 0x0137, 0x091B,
      0x130D, 0xFFFF }, { 0x0232, 0x0402, 0x0621, 0x0429, 0xFFFF }, { 0x0228, 0x051C, 0x0713, 0x100B, 0x0C1F, 0xFFFF }, {
      0x0320, 0x0335, 0x0A05, 0x0817, 0xFFFF }, { 0x0623, 0x0527, 0xFFFF }, { 0x0416, 0x061E, 0x0E0E, 0x0711, 0x0E09, 0x012F,
      0xFFFF }, { 0x0322, 0x0504, 0x080A, 0x0919, 0x1D0F, 0xFFFF }, { 0x0631, 0x0903, 0x0815, 0x0C07, 0x042B, 0x032D, 0x0B1D,
      0xFFFF }, { 0x022A, 0x0801, 0x0533, 0x0625, 0x0237, 0x0A1B, 0xFFFF }, { 0x0330, 0x0414, 0x0136, 0x0708, 0x0721, 0x0529,
      0x140D, 0xFFFF }, { 0x0400, 0x0324, 0x0606, 0x0038, 0x0039, 0x110B, 0x0D1F, 0xFFFF }, { 0x051A, 0x0813, 0x0B05, 0x0917,
      0xFFFF }, { 0x0723, 0x0435, 0x0627, 0xFFFF }, { 0x0412, 0x0234, 0x0F09, 0x022F, 0xFFFF }, { 0x0326, 0x0A0C, 0x012E,
      0x0811, 0x0A19, 0x1E0F, 0xFFFF }, { 0x0731, 0x0A03, 0x0915, 0x0D07, 0x052B, 0xFFFF }, { 0x0410, 0x0901, 0x0633, 0x0725,
      0x0337, 0x0B1B, 0x042D, 0x0C1D, 0xFFFF }, { 0x0518, 0x022C, 0x0629, 0x150D, 0xFFFF }, { 0x0332, 0x0502, 0x0821, 0x0139,
      0x120B, 0x0E1F, 0xFFFF }, { 0x0328, 0x061C, 0x0913, 0x0A17, 0xFFFF }, { 0x0420, 0x0535, 0x0C05, 0x0727, 0xFFFF }, {
      0x0823, 0x032F, 0xFFFF }, { 0x0516, 0x071E, 0x0F0E, 0x0911, 0x0B19, 0x1009, 0x1F0F, 0xFFFF }, { 0x0422, 0x0604, 0x090A,
      0x0B03, 0x0A15, 0x0E07, 0x062B, 0xFFFF }, { 0x0831, 0x0A01, 0x0733, 0x052D, 0x0D1D, 0xFFFF }, { 0x032A, 0x0825, 0x0437,
      0x0729, 0x0C1B, 0x160D, 0xFFFF }, { 0x0430, 0x0514, 0x0236, 0x0808, 0x0921, 0x0239, 0x130B, 0x0F1F, 0xFFFF }, { 0x0500,
      0x0424, 0x0706, 0x0138, 0x0A13, 0x0B17, 0xFFFF }, { 0x061A, 0x0635, 0x0D05, 0xFFFF }, { 0x0923, 0x0827, 0xFFFF }, {
      0x0512, 0x0334, 0x003A, 0x0A11, 0x1109, 0x003B, 0x042F, 0xFFFF }, { 0x0426, 0x0B0C, 0x022E, 0x0B15, 0x0F07, 0x0C19,
      0x072B, 0xFFFF }, { 0x0931, 0x0B01, 0x0C03, 0x062D, 0x0E1D, 0xFFFF }, { 0x0510, 0x0833, 0x0925, 0x0537, 0x0D1B, 0x170D,
      0xFFFF }, { 0x0618, 0x032C, 0x0A21, 0x0339, 0x0829, 0xFFFF }, { 0x0432, 0x0602, 0x0B13, 0x140B, 0x101F, 0xFFFF }, {
      0x0428, 0x071C, 0x0735, 0x0E05, 0x0C17, 0xFFFF }, { 0x0520, 0x0A23, 0x0927, 0xFFFF }, { 0x0B11, 0x1209, 0x013B, 0x052F,
      0xFFFF }, { 0x0616, 0x081E, 0x0D19, 0xFFFF }, { 0x0522, 0x0704, 0x0A0A, 0x0A31, 0x0D03, 0x0C15, 0x1007, 0x082B, 0x072D,
      0x0F1D, 0xFFFF }, { 0x0C01, 0x0933, 0x0A25, 0x0637, 0x0E1B, 0xFFFF }, { 0x042A, 0x0B21, 0x0929, 0x180D, 0xFFFF }, {
      0x0530, 0x0614, 0x0336, 0x0908, 0x0439, 0x150B, 0x111F, 0xFFFF }, { 0x0600, 0x0524, 0x0806, 0x0238, 0x0C13, 0x0F05,
      0x0D17, 0xFFFF }, { 0x071A, 0x0B23, 0x0835, 0x0A27, 0xFFFF }, { 0x1309, 0x023B, 0x062F, 0xFFFF }, { 0x0612, 0x0434,
      0x013A, 0x0C11, 0x0E19, 0xFFFF }, { 0x0526, 0x0C0C, 0x032E, 0x0B31, 0x0E03, 0x0D15, 0x1107, 0x092B, 0xFFFF }, { 0x0D01,
      0x0A33, 0x0B25, 0x0737, 0x0F1B, 0x082D, 0x101D, 0xFFFF }, { 0x0610, 0x0A29, 0x190D, 0xFFFF }, { 0x0718, 0x042C, 0x0C21,
      0x0539, 0x160B, 0x121F, 0xFFFF }, { 0x0532, 0x0702, 0x0D13, 0x0E17, 0xFFFF }, { 0x0528, 0x081C, 0x0935, 0x1005, 0x0B27,
      0xFFFF }, { 0x0620, 0x0C23, 0x033B, 0x072F, 0xFFFF }, { 0x0D11, 0x0F19, 0x1409, 0xFFFF }, { 0x0716, 0x003C, 0x091E,
      0x0F03, 0x0E15, 0x1207, 0x0A2B, 0x003D, 0xFFFF }, { 0x0622, 0x0804, 0x0B0A, 0x0C31, 0x0E01, 0x0B33, 0x092D, 0x111D,
      0xFFFF }, { 0x0C25, 0x0837, 0x0B29, 0x101B, 0x1A0D, 0xFFFF }, { 0x052A, 0x0D21, 0x0639, 0x170B, 0x131F, 0xFFFF }, {
      0x0630, 0x0714, 0x0436, 0x0A08, 0x0E13, 0x0F17, 0xFFFF }, { 0x0700, 0x0624, 0x0906, 0x0338, 0x0A35, 0x1105, 0xFFFF }, {
      0x081A, 0x0D23, 0x0C27, 0xFFFF }, { 0x0E11, 0x1509, 0x043B, 0x082F, 0xFFFF }, { 0x0712, 0x0534, 0x023A, 0x0F15, 0x1307,
      0x1019, 0x0B2B, 0x013D, 0xFFFF }, { 0x0626, 0x0D0C, 0x042E, 0x0D31, 0x0F01, 0x1003, 0x0A2D, 0x121D, 0xFFFF }, { 0x0C33,
      0x0D25, 0x0937, 0x111B, 0x1B0D, 0xFFFF }, { 0x0710, 0x0E21, 0x0739, 0x0C29, 0xFFFF }, { 0x0818, 0x052C, 0x0F13, 0x180B,
      0x141F, 0xFFFF }, { 0x0632, 0x0802, 0x0B35, 0x1205, 0x1017, 0xFFFF }, { 0x0628, 0x091C, 0x0E23, 0x0D27, 0xFFFF }, {
      0x0720, 0x0F11, 0x1609, 0x053B, 0x092F, 0xFFFF }, { 0x1119, 0x023D, 0xFFFF }, { 0x0816, 0x013C, 0x0A1E, 0x0E31, 0x1103,
      0x1015, 0x1407, 0x0C2B, 0x0B2D, 0x131D, 0xFFFF }, { 0x0722, 0x0904, 0x0C0A, 0x1001, 0x0D33, 0x0E25, 0x0A37, 0x121B,
      0xFFFF }, { 0x0F21, 0x0D29, 0x1C0D, 0xFFFF }, { 0x062A, 0x0839, 0x190B, 0x151F, 0xFFFF }, { 0x0730, 0x0814, 0x0536,
      0x0B08, 0x1013, 0x1305, 0x1117, 0xFFFF }, { 0x0800, 0x0724, 0x0A06, 0x0438, 0x0F23, 0x0C35, 0x0E27, 0xFFFF }, { 0x091A,
      0x1709, 0x063B, 0x0A2F, 0xFFFF }, { 0x1011, 0x1219, 0x033D, 0xFFFF }, { 0x0812, 0x0634, 0x033A, 0x0F31, 0x1203, 0x1115,
      0x1507, 0x0D2B, 0xFFFF }, { 0x0726, 0x0E0C, 0x052E, 0x1101, 0x0E33, 0x0F25, 0x0B37, 0x131B, 0x0C2D, 0x141D, 0xFFFF }, {
      0x0E29, 0x1D0D, 0xFFFF }, { 0x0810, 0x1021, 0x0939, 0x1A0B, 0x161F, 0xFFFF }, { 0x0918, 0x062C, 0x1113, 0x1217, 0xFFFF
      }, { 0x0732, 0x0902, 0x0D35, 0x1405, 0x0F27, 0xFFFF }, { 0x0728, 0x0A1C, 0x1023, 0x073B, 0x0B2F, 0xFFFF }, { 0x0820,
      0x1111, 0x1319, 0x1809, 0xFFFF }, { 0x1303, 0x1215, 0x1607, 0x0E2B, 0x043D, 0xFFFF }, { 0x0916, 0x023C, 0x0B1E, 0x1031,
      0x1201, 0x0F33, 0x0D2D, 0x151D, 0xFFFF }, { 0x0822, 0x0A04, 0x0D0A, 0x1025, 0x0C37, 0x0F29, 0x141B, 0x1E0D, 0xFFFF }, {
      0x1121, 0x0A39, 0x1B0B, 0x171F, 0xFFFF }, { 0x072A, 0x1213, 0x1317, 0xFFFF }, { 0x0830, 0x0914, 0x0636, 0x0C08, 0x0E35,
      0x1505, 0xFFFF }, { 0x0900, 0x0824, 0x0B06, 0x0538, 0x1123, 0x1027, 0xFFFF }, { 0x0A1A, 0x1211, 0x1909, 0x083B, 0x0C2F,
      0xFFFF }, { 0x1315, 0x1707, 0x1419, 0x0F2B, 0x053D, 0xFFFF }, { 0x0912, 0x0734, 0x043A, 0x1131, 0x1301, 0x1403, 0x0E2D,
      0x161D, 0xFFFF }, { 0x0826, 0x0F0C, 0x062E, 0x1033, 0x1125, 0x0D37, 0x151B, 0x1F0D, 0xFFFF }, { 0x1221, 0x0B39, 0x1029,
      0xFFFF }, { 0x0910, 0x1313, 0x1C0B, 0x181F, 0xFFFF }, { 0x0A18, 0x072C, 0x0F35, 0x1605, 0x1417, 0xFFFF }, { 0x0832,
      0x0A02, 0x1223, 0x1127, 0xFFFF }, { 0x0828, 0x0B1C, 0x1311, 0x1A09, 0x093B, 0x0D2F, 0xFFFF }, { 0x0920, 0x1519, 0x063D,
      0xFFFF }, { 0x1231, 0x1503, 0x1415, 0x1807, 0x102B, 0x0F2D, 0x171D, 0xFFFF }, { 0x0A16, 0x033C, 0x0C1E, 0x1401, 0x1133,
      0x1225, 0x0E37, 0x161B, 0xFFFF }, { 0x0922, 0x0B04, 0x0E0A, 0x1321, 0x1129, 0xFFFF }, { 0x0C39, 0x1D0B, 0x191F, 0xFFFF
      }, { 0x082A, 0x1413, 0x1705, 0x1517, 0xFFFF }, { 0x0930, 0x0A14, 0x0736, 0x0D08, 0x1323, 0x1035, 0x1227, 0xFFFF }, {
      0x0A00, 0x0924, 0x0C06, 0x0638, 0x1B09, 0x0A3B, 0x0E2F, 0xFFFF }, { 0x0B1A, 0x1411, 0x1619, 0x073D, 0xFFFF }, { 0x1331,
      0x1603, 0x1515, 0x1907, 0x112B, 0xFFFF }, { 0x0A12, 0x0834, 0x053A, 0x1501, 0x1233, 0x1325, 0x0F37, 0x171B, 0x102D,
      0x181D, 0xFFFF }, { 0x0926, 0x072E, 0x1229, 0xFFFF }, { 0x1421, 0x0D39, 0x1E0B, 0x1A1F, 0xFFFF }, { 0x0A10, 0x1513,
      0x1617, 0xFFFF }, { 0x0B18, 0x082C, 0x1135, 0x1805, 0x1327, 0xFFFF }, { 0x0932, 0x0B02, 0x1423, 0x0B3B, 0x0F2F, 0xFFFF
      }, { 0x0928, 0x0C1C, 0x1511, 0x1719, 0x1C09, 0xFFFF }, { 0x0A20, 0x1703, 0x1615, 0x1A07, 0x122B, 0x083D, 0xFFFF }, {
      0x1431, 0x1601, 0x1333, 0x112D, 0x191D, 0xFFFF }, { 0x0B16, 0x043C, 0x0D1E, 0x1425, 0x1037, 0x1329, 0x181B, 0xFFFF }, {
      0x0A22, 0x0C04, 0x0F0A, 0x1521, 0x0E39, 0x1F0B, 0x1B1F, 0xFFFF }, { 0x1613, 0x1717, 0xFFFF }, { 0x092A, 0x1235, 0x1905,
      0xFFFF }, { 0x0A30, 0x0B14, 0x0836, 0x0E08, 0x1523, 0x1427, 0xFFFF }, { 0x0B00, 0x0A24, 0x0D06, 0x0738, 0x1611, 0x1D09,
      0x0C3B, 0x102F, 0xFFFF }, { 0x0C1A, 0x1715, 0x1B07, 0x1819, 0x132B, 0x093D, 0xFFFF }, { 0x1531, 0x1701, 0x1803, 0x122D,
      0x1A1D, 0xFFFF }, { 0x0B12, 0x0934, 0x063A, 0x1433, 0x1525, 0x1137, 0x191B, 0xFFFF }, { 0x0A26, 0x003E, 0x082E, 0x1621,
      0x0F39, 0x1429, 0x003F, 0xFFFF }, { 0x1713, 0x1C1F, 0xFFFF }, { 0x0B10, 0x1335, 0x1A05, 0x1817, 0xFFFF }, { 0x0C18,
      0x092C, 0x1623, 0x1527, 0xFFFF }, { 0x0A32, 0x0C02, 0x1711, 0x1E09, 0x0D3B, 0x112F, 0xFFFF }, { 0x0A28, 0x0D1C, 0x1919,
      0x0A3D, 0xFFFF }, { 0x0B20, 0x1631, 0x1903, 0x1815, 0x1C07, 0x142B, 0x132D, 0x1B1D, 0xFFFF }, { 0x1801, 0x1533, 0x1625,
      0x1237, 0x1A1B, 0xFFFF }, { 0x0C16, 0x053C, 0x0E1E, 0x1721, 0x1529, 0x013F, 0xFFFF }, { 0x0B22, 0x0D04, 0x1039, 0x1D1F,
      0xFFFF }, { 0x1813, 0x1B05, 0x1917, 0xFFFF }, { 0x0A2A, 0x1723, 0x1435, 0x1627, 0xFFFF }, { 0x0B30, 0x0C14, 0x0936,
      0x0F08, 0x1F09, 0x0E3B, 0x122F, 0xFFFF }, { 0x0C00, 0x0B24, 0x0E06, 0x0838, 0x1811, 0x1A19, 0x0B3D, 0xFFFF }, { 0x0D1A,
      0x1731, 0x1A03, 0x1915, 0x1D07, 0x152B, 0xFFFF }, { 0x1901, 0x1633, 0x1725, 0x1337, 0x1B1B, 0x142D, 0x1C1D, 0xFFFF }, {
      0x0C12, 0x0A34, 0x073A, 0x1629, 0x023F, 0xFFFF }, { 0x0B26, 0x013E, 0x092E, 0x1821, 0x1139, 0x1E1F, 0xFFFF }, { 0x1913,
      0x1A17, 0xFFFF }, { 0x0C10, 0x1535, 0x1C05, 0x1727, 0xFFFF }, { 0x0D18, 0x0A2C, 0x1823, 0x0F3B, 0x132F, 0xFFFF }, {
      0x0B32, 0x0D02, 0x1911, 0x1B19, 0xFFFF }, { 0x0B28, 0x0E1C, 0x1B03, 0x1A15, 0x1E07, 0x162B, 0x0C3D, 0xFFFF }, { 0x0C20,
      0x1831, 0x1A01, 0x1733, 0x152D, 0x1D1D, 0xFFFF }, { 0x1825, 0x1437, 0x1729, 0x1C1B, 0x033F, 0xFFFF }, { 0x0D16, 0x063C,
      0x0F1E, 0x1921, 0x1239, 0x1F1F, 0xFFFF }, { 0x0C22, 0x0E04, 0x1A13, 0x1B17, 0xFFFF }, { 0x1635, 0x1D05, 0xFFFF }, {
      0x0B2A, 0x1923, 0x1827, 0xFFFF }, { 0x0C30, 0x0D14, 0x0A36, 0x1A11, 0x103B, 0x142F, 0xFFFF }, { 0x0D00, 0x0C24, 0x0F06,
      0x0938, 0x1B15, 0x1F07, 0x1C19, 0x172B, 0x0D3D, 0xFFFF }, { 0x0E1A, 0x1931, 0x1B01, 0x1C03, 0x162D, 0x1E1D, 0xFFFF }, {
      0x1833, 0x1925, 0x1537, 0x1D1B, 0xFFFF }, { 0x0D12, 0x0B34, 0x083A, 0x1A21, 0x1339, 0x1829, 0x043F, 0xFFFF }, { 0x0C26,
      0x023E, 0x0A2E, 0x1B13, 0xFFFF }, { 0x1735, 0x1E05, 0x1C17, 0xFFFF }, { 0x0D10, 0x1A23, 0x1927, 0xFFFF }, { 0x0E18,
      0x0B2C, 0x1B11, 0x113B, 0x152F, 0xFFFF }, { 0x0C32, 0x0E02, 0x1D19, 0x0E3D, 0xFFFF }, { 0x0C28, 0x0F1C, 0x1A31, 0x1D03,
      0x1C15, 0x182B, 0x172D, 0x1F1D, 0xFFFF }, { 0x0D20, 0x1C01, 0x1933, 0x1A25, 0x1637, 0x1E1B, 0xFFFF }, { 0x1B21, 0x1929,
      0x053F, 0xFFFF }, { 0x0E16, 0x073C, 0x1439, 0xFFFF }, { 0x0D22, 0x0F04, 0x1C13, 0x1F05, 0x1D17, 0xFFFF }, { 0x1B23,
      0x1835, 0x1A27, 0xFFFF }, { 0x0C2A, 0x123B, 0x162F, 0xFFFF }, { 0x0D30, 0x0E14, 0x0B36, 0x1C11, 0x1E19, 0x0F3D, 0xFFFF
      }, { 0x0E00, 0x0D24, 0x0A38, 0x1B31, 0x1E03, 0x1D15, 0x192B, 0xFFFF }, { 0x0F1A, 0x1D01, 0x1A33, 0x1B25, 0x1737, 0x1F1B,
      0x182D, 0xFFFF }, { 0x1A29, 0x063F, 0xFFFF }, { 0x0E12, 0x0C34, 0x093A, 0x1C21, 0x1539, 0xFFFF }, { 0x0D26, 0x033E,
      0x0B2E, 0x1D13, 0x1E17, 0xFFFF }, { 0x1935, 0x1B27, 0xFFFF }, { 0x0E10, 0x1C23, 0x133B, 0x172F, 0xFFFF }, { 0x0F18,
      0x0C2C, 0x1D11, 0x1F19, 0xFFFF }, { 0x0D32, 0x0F02, 0x1F03, 0x1E15, 0x1A2B, 0x103D, 0xFFFF }, { 0x0D28, 0x1C31, 0x1E01,
      0x1B33, 0x192D, 0xFFFF }, { 0x0E20, 0x1C25, 0x1837, 0x1B29, 0x073F, 0xFFFF }, { 0x1D21, 0x1639, 0xFFFF }, { 0x0F16,
      0x083C, 0x1E13, 0x1F17, 0xFFFF }, { 0x0E22, 0x1A35, 0xFFFF }, { 0x1D23, 0x1C27, 0xFFFF }, { 0x0D2A, 0x1E11, 0x143B,
      0x182F, 0xFFFF }, { 0x0E30, 0x0F14, 0x0C36, 0x1F15, 0x1B2B, 0x113D, 0xFFFF }, { 0x0F00, 0x0E24, 0x0B38, 0x1D31, 0x1F01,
      0x1A2D, 0xFFFF }, { 0x1C33, 0x1D25, 0x1937, 0xFFFF }, { 0x1E21, 0x1739, 0x1C29, 0x083F, 0xFFFF }, { 0x0F12, 0x0D34,
      0x0A3A, 0x1F13, 0xFFFF }, { 0x0E26, 0x043E, 0x0C2E, 0x1B35, 0xFFFF }, { 0x1E23, 0x1D27, 0xFFFF }, { 0x0F10, 0x1F11,
      0x153B, 0x192F, 0xFFFF }, { 0x0D2C, 0x123D, 0xFFFF },
   };

   struct etc1_block
   {
      // big endian uint64:
      // bit ofs:  56  48  40  32  24  16   8   0
      // byte ofs: b0, b1, b2, b3, b4, b5, b6, b7 
      union 
      {
         uint64 m_uint64;
         uint8 m_bytes[8];
      };

      uint8 m_low_color[2];
      uint8 m_high_color[2];

      enum { cNumSelectorBytes = 4 };
      uint8 m_selectors[cNumSelectorBytes];

      inline void clear()
      {
         zero_this(this);
      }

      inline uint get_byte_bits(uint ofs, uint num) const
      {
         RG_ETC1_ASSERT((ofs + num) <= 64U);
         RG_ETC1_ASSERT(num && (num <= 8U));
         RG_ETC1_ASSERT((ofs >> 3) == ((ofs + num - 1) >> 3));
         const uint byte_ofs = 7 - (ofs >> 3);
         const uint byte_bit_ofs = ofs & 7;
         return (m_bytes[byte_ofs] >> byte_bit_ofs) & ((1 << num) - 1);
      }

      inline void set_byte_bits(uint ofs, uint num, uint bits)
      {
         RG_ETC1_ASSERT((ofs + num) <= 64U);
         RG_ETC1_ASSERT(num && (num < 32U));
         RG_ETC1_ASSERT((ofs >> 3) == ((ofs + num - 1) >> 3));
         RG_ETC1_ASSERT(bits < (1U << num));
         const uint byte_ofs = 7 - (ofs >> 3);
         const uint byte_bit_ofs = ofs & 7;
         const uint mask = (1 << num) - 1;
         m_bytes[byte_ofs] &= ~(mask << byte_bit_ofs);
         m_bytes[byte_ofs] |= (bits << byte_bit_ofs);
      }

      // false = left/right subblocks
      // true = upper/lower subblocks
      inline bool get_flip_bit() const 
      {
         return (m_bytes[3] & 1) != 0;
      }   

      inline void set_flip_bit(bool flip)
      {
         m_bytes[3] &= ~1;
         m_bytes[3] |= static_cast<uint8>(flip);
      }

      inline bool get_diff_bit() const
      {
         return (m_bytes[3] & 2) != 0;
      }

      inline void set_diff_bit(bool diff)
      {
         m_bytes[3] &= ~2;
         m_bytes[3] |= (static_cast<uint>(diff) << 1);
      }

      // Returns intensity modifier table (0-7) used by subblock subblock_id.
      // subblock_id=0 left/top (CW 1), 1=right/bottom (CW 2)
      inline uint get_inten_table(uint subblock_id) const
      {
         RG_ETC1_ASSERT(subblock_id < 2);
         const uint ofs = subblock_id ? 2 : 5;
         return (m_bytes[3] >> ofs) & 7;
      }

      // Sets intensity modifier table (0-7) used by subblock subblock_id (0 or 1)
      inline void set_inten_table(uint subblock_id, uint t)
      {
         RG_ETC1_ASSERT(subblock_id < 2);
         RG_ETC1_ASSERT(t < 8);
         const uint ofs = subblock_id ? 2 : 5;
         m_bytes[3] &= ~(7 << ofs);
         m_bytes[3] |= (t << ofs);
      }

      // Returned selector value ranges from 0-3 and is a direct index into g_etc1_inten_tables.
      inline uint get_selector(uint x, uint y) const
      {
         RG_ETC1_ASSERT((x | y) < 4);

         const uint bit_index = x * 4 + y;
         const uint byte_bit_ofs = bit_index & 7;
         const uint8 *p = &m_bytes[7 - (bit_index >> 3)];
         const uint lsb = (p[0] >> byte_bit_ofs) & 1;
         const uint msb = (p[-2] >> byte_bit_ofs) & 1;
         const uint val = lsb | (msb << 1);

         return g_etc1_to_selector_index[val];
      }

      // Selector "val" ranges from 0-3 and is a direct index into g_etc1_inten_tables.
      inline void set_selector(uint x, uint y, uint val)
      {
         RG_ETC1_ASSERT((x | y | val) < 4);
         const uint bit_index = x * 4 + y;

         uint8 *p = &m_bytes[7 - (bit_index >> 3)];

         const uint byte_bit_ofs = bit_index & 7;
         const uint mask = 1 << byte_bit_ofs;

         const uint etc1_val = g_selector_index_to_etc1[val];

         const uint lsb = etc1_val & 1;
         const uint msb = etc1_val >> 1;

         p[0] &= ~mask;
         p[0] |= (lsb << byte_bit_ofs);

         p[-2] &= ~mask;
         p[-2] |= (msb << byte_bit_ofs);
      }

      inline void set_base4_color(uint idx, uint16 c)
      {
         if (idx)
         {
            set_byte_bits(cETC1AbsColor4R2BitOffset, 4, (c >> 8) & 15);
            set_byte_bits(cETC1AbsColor4G2BitOffset, 4, (c >> 4) & 15);
            set_byte_bits(cETC1AbsColor4B2BitOffset, 4, c & 15);
         }
         else
         {
            set_byte_bits(cETC1AbsColor4R1BitOffset, 4, (c >> 8) & 15);
            set_byte_bits(cETC1AbsColor4G1BitOffset, 4, (c >> 4) & 15);
            set_byte_bits(cETC1AbsColor4B1BitOffset, 4, c & 15);
         }
      }

      inline uint16 get_base4_color(uint idx) const
      {
         uint r, g, b;
         if (idx)
         {
            r = get_byte_bits(cETC1AbsColor4R2BitOffset, 4);
            g = get_byte_bits(cETC1AbsColor4G2BitOffset, 4);
            b = get_byte_bits(cETC1AbsColor4B2BitOffset, 4);
         }
         else
         {
            r = get_byte_bits(cETC1AbsColor4R1BitOffset, 4);
            g = get_byte_bits(cETC1AbsColor4G1BitOffset, 4);
            b = get_byte_bits(cETC1AbsColor4B1BitOffset, 4);
         }
         return static_cast<uint16>(b | (g << 4U) | (r << 8U));
      }

      inline void set_base5_color(uint16 c)
      {
         set_byte_bits(cETC1BaseColor5RBitOffset, 5, (c >> 10) & 31);
         set_byte_bits(cETC1BaseColor5GBitOffset, 5, (c >> 5) & 31);
         set_byte_bits(cETC1BaseColor5BBitOffset, 5, c & 31);
      }

      inline uint16 get_base5_color() const
      {
         const uint r = get_byte_bits(cETC1BaseColor5RBitOffset, 5);
         const uint g = get_byte_bits(cETC1BaseColor5GBitOffset, 5);
         const uint b = get_byte_bits(cETC1BaseColor5BBitOffset, 5);
         return static_cast<uint16>(b | (g << 5U) | (r << 10U));
      }

      void set_delta3_color(uint16 c)
      {
         set_byte_bits(cETC1DeltaColor3RBitOffset, 3, (c >> 6) & 7);
         set_byte_bits(cETC1DeltaColor3GBitOffset, 3, (c >> 3) & 7);
         set_byte_bits(cETC1DeltaColor3BBitOffset, 3, c & 7);
      }

      inline uint16 get_delta3_color() const
      {
         const uint r = get_byte_bits(cETC1DeltaColor3RBitOffset, 3);
         const uint g = get_byte_bits(cETC1DeltaColor3GBitOffset, 3);
         const uint b = get_byte_bits(cETC1DeltaColor3BBitOffset, 3);
         return static_cast<uint16>(b | (g << 3U) | (r << 6U));
      }

      // Base color 5
      static uint16 pack_color5(const color_quad_u8& color, bool scaled, uint bias = 127U);
      static uint16 pack_color5(uint r, uint g, uint b, bool scaled, uint bias = 127U);

      static color_quad_u8 unpack_color5(uint16 packed_color5, bool scaled, uint alpha = 255U);
      static void unpack_color5(uint& r, uint& g, uint& b, uint16 packed_color, bool scaled);

      static bool unpack_color5(color_quad_u8& result, uint16 packed_color5, uint16 packed_delta3, bool scaled, uint alpha = 255U);
      static bool unpack_color5(uint& r, uint& g, uint& b, uint16 packed_color5, uint16 packed_delta3, bool scaled, uint alpha = 255U);

      // Delta color 3
      // Inputs range from -4 to 3 (cETC1ColorDeltaMin to cETC1ColorDeltaMax)
      static uint16 pack_delta3(int r, int g, int b);

      // Results range from -4 to 3 (cETC1ColorDeltaMin to cETC1ColorDeltaMax)
      static void unpack_delta3(int& r, int& g, int& b, uint16 packed_delta3);

      // Abs color 4
      static uint16 pack_color4(const color_quad_u8& color, bool scaled, uint bias = 127U);
      static uint16 pack_color4(uint r, uint g, uint b, bool scaled, uint bias = 127U);

      static color_quad_u8 unpack_color4(uint16 packed_color4, bool scaled, uint alpha = 255U);
      static void unpack_color4(uint& r, uint& g, uint& b, uint16 packed_color4, bool scaled);

      // subblock colors
      static void get_diff_subblock_colors(color_quad_u8* pDst, uint16 packed_color5, uint table_idx);
      static bool get_diff_subblock_colors(color_quad_u8* pDst, uint16 packed_color5, uint16 packed_delta3, uint table_idx);
      static void get_abs_subblock_colors(color_quad_u8* pDst, uint16 packed_color4, uint table_idx);

      static inline void unscaled_to_scaled_color(color_quad_u8& dst, const color_quad_u8& src, bool color4)
      {
         if (color4)
         {
            dst.r = src.r | (src.r << 4);
            dst.g = src.g | (src.g << 4);
            dst.b = src.b | (src.b << 4);
         }
         else
         {
            dst.r = (src.r >> 2) | (src.r << 3);
            dst.g = (src.g >> 2) | (src.g << 3);
            dst.b = (src.b >> 2) | (src.b << 3);
         }
         dst.a = src.a;
      }
   };

   // Returns pointer to sorted array.
   template<typename T, typename Q>
   T* indirect_radix_sort(uint num_indices, T* pIndices0, T* pIndices1, const Q* pKeys, uint key_ofs, uint key_size, bool init_indices)
   {  
      RG_ETC1_ASSERT((key_ofs >= 0) && (key_ofs < sizeof(T)));
      RG_ETC1_ASSERT((key_size >= 1) && (key_size <= 4));

      if (init_indices)
      {
         T* p = pIndices0;
         T* q = pIndices0 + (num_indices >> 1) * 2;
         uint i;
         for (i = 0; p != q; p += 2, i += 2)
         {
            p[0] = static_cast<T>(i);
            p[1] = static_cast<T>(i + 1); 
         }

         if (num_indices & 1)
            *p = static_cast<T>(i);
      }

      uint hist[256 * 4];

      memset(hist, 0, sizeof(hist[0]) * 256 * key_size);

#define RG_ETC1_GET_KEY(p) (*(const uint*)((const uint8*)(pKeys + *(p)) + key_ofs))
#define RG_ETC1_GET_KEY_FROM_INDEX(i) (*(const uint*)((const uint8*)(pKeys + (i)) + key_ofs))

      if (key_size == 4)
      {
         T* p = pIndices0;
         T* q = pIndices0 + num_indices;
         for ( ; p != q; p++)
         {
            const uint key = RG_ETC1_GET_KEY(p);

            hist[        key        & 0xFF]++;
            hist[256 + ((key >>  8) & 0xFF)]++;
            hist[512 + ((key >> 16) & 0xFF)]++;
            hist[768 + ((key >> 24) & 0xFF)]++;
         }
      }
      else if (key_size == 3)
      {
         T* p = pIndices0;
         T* q = pIndices0 + num_indices;
         for ( ; p != q; p++)
         {
            const uint key = RG_ETC1_GET_KEY(p);

            hist[        key        & 0xFF]++;
            hist[256 + ((key >>  8) & 0xFF)]++;
            hist[512 + ((key >> 16) & 0xFF)]++;
         }
      }   
      else if (key_size == 2)
      {
         T* p = pIndices0;
         T* q = pIndices0 + (num_indices >> 1) * 2;

         for ( ; p != q; p += 2)
         {
            const uint key0 = RG_ETC1_GET_KEY(p);
            const uint key1 = RG_ETC1_GET_KEY(p+1);

            hist[        key0         & 0xFF]++;
            hist[256 + ((key0 >>  8) & 0xFF)]++;

            hist[        key1        & 0xFF]++;
            hist[256 + ((key1 >>  8) & 0xFF)]++;
         }

         if (num_indices & 1)
         {
            const uint key = RG_ETC1_GET_KEY(p);

            hist[        key        & 0xFF]++;
            hist[256 + ((key >>  8) & 0xFF)]++;
         }
      }      
      else
      {
         RG_ETC1_ASSERT(key_size == 1);
         if (key_size != 1)
            return NULL;

         T* p = pIndices0;
         T* q = pIndices0 + (num_indices >> 1) * 2;

         for ( ; p != q; p += 2)
         {
            const uint key0 = RG_ETC1_GET_KEY(p);
            const uint key1 = RG_ETC1_GET_KEY(p+1);

            hist[key0 & 0xFF]++;
            hist[key1 & 0xFF]++;
         }

         if (num_indices & 1)
         {
            const uint key = RG_ETC1_GET_KEY(p);

            hist[key & 0xFF]++;
         }
      }      

      T* pCur = pIndices0;
      T* pNew = pIndices1;

      for (uint pass = 0; pass < key_size; pass++)
      {
         const uint* pHist = &hist[pass << 8];

         uint offsets[256];

         uint cur_ofs = 0;
         for (uint i = 0; i < 256; i += 2)
         {
            offsets[i] = cur_ofs;
            cur_ofs += pHist[i];

            offsets[i+1] = cur_ofs;
            cur_ofs += pHist[i+1];
         }

         const uint pass_shift = pass << 3;

         T* p = pCur;
         T* q = pCur + (num_indices >> 1) * 2;

         for ( ; p != q; p += 2)
         {
            uint index0 = p[0];
            uint index1 = p[1];

            uint c0 = (RG_ETC1_GET_KEY_FROM_INDEX(index0) >> pass_shift) & 0xFF;
            uint c1 = (RG_ETC1_GET_KEY_FROM_INDEX(index1) >> pass_shift) & 0xFF;

            if (c0 == c1)
            {
               uint dst_offset0 = offsets[c0];

               offsets[c0] = dst_offset0 + 2;

               pNew[dst_offset0] = static_cast<T>(index0);
               pNew[dst_offset0 + 1] = static_cast<T>(index1);
            }
            else
            {
               uint dst_offset0 = offsets[c0]++;
               uint dst_offset1 = offsets[c1]++;

               pNew[dst_offset0] = static_cast<T>(index0);
               pNew[dst_offset1] = static_cast<T>(index1);
            }
         }

         if (num_indices & 1)
         {
            uint index = *p;
            uint c = (RG_ETC1_GET_KEY_FROM_INDEX(index) >> pass_shift) & 0xFF;

            uint dst_offset = offsets[c];
            offsets[c] = dst_offset + 1;

            pNew[dst_offset] = static_cast<T>(index);
         }

         T* t = pCur;
         pCur = pNew;
         pNew = t;
      }            

      return pCur;
   }

#undef RG_ETC1_GET_KEY
#undef RG_ETC1_GET_KEY_FROM_INDEX

   uint16 etc1_block::pack_color5(const color_quad_u8& color, bool scaled, uint bias)
   {
      return pack_color5(color.r, color.g, color.b, scaled, bias);
   }
   
   uint16 etc1_block::pack_color5(uint r, uint g, uint b, bool scaled, uint bias)
   {
      if (scaled)
      {
         r = (r * 31U + bias) / 255U;
         g = (g * 31U + bias) / 255U;
         b = (b * 31U + bias) / 255U;
      }

      r = rg_etc1::minimum(r, 31U);
      g = rg_etc1::minimum(g, 31U);
      b = rg_etc1::minimum(b, 31U);

      return static_cast<uint16>(b | (g << 5U) | (r << 10U));
   }

   color_quad_u8 etc1_block::unpack_color5(uint16 packed_color5, bool scaled, uint alpha)
   {
      uint b = packed_color5 & 31U;
      uint g = (packed_color5 >> 5U) & 31U;
      uint r = (packed_color5 >> 10U) & 31U;

      if (scaled)
      {
         b = (b << 3U) | (b >> 2U);
         g = (g << 3U) | (g >> 2U);
         r = (r << 3U) | (r >> 2U);
      }

      return color_quad_u8(cNoClamp, r, g, b, rg_etc1::minimum(alpha, 255U));
   }

   void etc1_block::unpack_color5(uint& r, uint& g, uint& b, uint16 packed_color5, bool scaled)
   {
      color_quad_u8 c(unpack_color5(packed_color5, scaled, 0));
      r = c.r;
      g = c.g;
      b = c.b;
   }

   bool etc1_block::unpack_color5(color_quad_u8& result, uint16 packed_color5, uint16 packed_delta3, bool scaled, uint alpha)
   {
      int dc_r, dc_g, dc_b;
      unpack_delta3(dc_r, dc_g, dc_b, packed_delta3);
      
      int b = (packed_color5 & 31U) + dc_b;
      int g = ((packed_color5 >> 5U) & 31U) + dc_g;
      int r = ((packed_color5 >> 10U) & 31U) + dc_r;

      bool success = true;
      if (static_cast<uint>(r | g | b) > 31U)
      {
         success = false;
         r = rg_etc1::clamp<int>(r, 0, 31);
         g = rg_etc1::clamp<int>(g, 0, 31);
         b = rg_etc1::clamp<int>(b, 0, 31);
      }

      if (scaled)
      {
         b = (b << 3U) | (b >> 2U);
         g = (g << 3U) | (g >> 2U);
         r = (r << 3U) | (r >> 2U);
      }

      result.set_noclamp_rgba(r, g, b, rg_etc1::minimum(alpha, 255U));
      return success;
   }

   bool etc1_block::unpack_color5(uint& r, uint& g, uint& b, uint16 packed_color5, uint16 packed_delta3, bool scaled, uint alpha)
   {
      color_quad_u8 result;
      const bool success = unpack_color5(result, packed_color5, packed_delta3, scaled, alpha);
      r = result.r;
      g = result.g;
      b = result.b;
      return success;
   }
     
   uint16 etc1_block::pack_delta3(int r, int g, int b)
   {
      RG_ETC1_ASSERT((r >= cETC1ColorDeltaMin) && (r <= cETC1ColorDeltaMax));
      RG_ETC1_ASSERT((g >= cETC1ColorDeltaMin) && (g <= cETC1ColorDeltaMax));
      RG_ETC1_ASSERT((b >= cETC1ColorDeltaMin) && (b <= cETC1ColorDeltaMax));
      if (r < 0) r += 8;
      if (g < 0) g += 8;
      if (b < 0) b += 8;
      return static_cast<uint16>(b | (g << 3) | (r << 6));
   }
   
   void etc1_block::unpack_delta3(int& r, int& g, int& b, uint16 packed_delta3)
   {
      r = (packed_delta3 >> 6) & 7;
      g = (packed_delta3 >> 3) & 7;
      b = packed_delta3 & 7;
      if (r >= 4) r -= 8;
      if (g >= 4) g -= 8;
      if (b >= 4) b -= 8;
   }

   uint16 etc1_block::pack_color4(const color_quad_u8& color, bool scaled, uint bias)
   {
      return pack_color4(color.r, color.g, color.b, scaled, bias);
   }
   
   uint16 etc1_block::pack_color4(uint r, uint g, uint b, bool scaled, uint bias)
   {
      if (scaled)
      {
         r = (r * 15U + bias) / 255U;
         g = (g * 15U + bias) / 255U;
         b = (b * 15U + bias) / 255U;
      }

      r = rg_etc1::minimum(r, 15U);
      g = rg_etc1::minimum(g, 15U);
      b = rg_etc1::minimum(b, 15U);

      return static_cast<uint16>(b | (g << 4U) | (r << 8U));
   }

   color_quad_u8 etc1_block::unpack_color4(uint16 packed_color4, bool scaled, uint alpha)
   {
      uint b = packed_color4 & 15U;
      uint g = (packed_color4 >> 4U) & 15U;
      uint r = (packed_color4 >> 8U) & 15U;

      if (scaled)
      {
         b = (b << 4U) | b;
         g = (g << 4U) | g;
         r = (r << 4U) | r;
      }

      return color_quad_u8(cNoClamp, r, g, b, rg_etc1::minimum(alpha, 255U));
   }
   
   void etc1_block::unpack_color4(uint& r, uint& g, uint& b, uint16 packed_color4, bool scaled)
   {
      color_quad_u8 c(unpack_color4(packed_color4, scaled, 0));
      r = c.r;
      g = c.g;
      b = c.b;
   }

   void etc1_block::get_diff_subblock_colors(color_quad_u8* pDst, uint16 packed_color5, uint table_idx)
   {
      RG_ETC1_ASSERT(table_idx < cETC1IntenModifierValues);
      const int *pInten_modifer_table = &g_etc1_inten_tables[table_idx][0];

      uint r, g, b;
      unpack_color5(r, g, b, packed_color5, true);

      const int ir = static_cast<int>(r), ig = static_cast<int>(g), ib = static_cast<int>(b);

      const int y0 = pInten_modifer_table[0];
      pDst[0].set(ir + y0, ig + y0, ib + y0);

      const int y1 = pInten_modifer_table[1];
      pDst[1].set(ir + y1, ig + y1, ib + y1);

      const int y2 = pInten_modifer_table[2];
      pDst[2].set(ir + y2, ig + y2, ib + y2);

      const int y3 = pInten_modifer_table[3];
      pDst[3].set(ir + y3, ig + y3, ib + y3);
   }
   
   bool etc1_block::get_diff_subblock_colors(color_quad_u8* pDst, uint16 packed_color5, uint16 packed_delta3, uint table_idx)
   {
      RG_ETC1_ASSERT(table_idx < cETC1IntenModifierValues);
      const int *pInten_modifer_table = &g_etc1_inten_tables[table_idx][0];

      uint r, g, b;
      bool success = unpack_color5(r, g, b, packed_color5, packed_delta3, true);

      const int ir = static_cast<int>(r), ig = static_cast<int>(g), ib = static_cast<int>(b);

      const int y0 = pInten_modifer_table[0];
      pDst[0].set(ir + y0, ig + y0, ib + y0);

      const int y1 = pInten_modifer_table[1];
      pDst[1].set(ir + y1, ig + y1, ib + y1);

      const int y2 = pInten_modifer_table[2];
      pDst[2].set(ir + y2, ig + y2, ib + y2);

      const int y3 = pInten_modifer_table[3];
      pDst[3].set(ir + y3, ig + y3, ib + y3);

      return success;
   }
   
   void etc1_block::get_abs_subblock_colors(color_quad_u8* pDst, uint16 packed_color4, uint table_idx)
   {
      RG_ETC1_ASSERT(table_idx < cETC1IntenModifierValues);
      const int *pInten_modifer_table = &g_etc1_inten_tables[table_idx][0];

      uint r, g, b;
      unpack_color4(r, g, b, packed_color4, true);
      
      const int ir = static_cast<int>(r), ig = static_cast<int>(g), ib = static_cast<int>(b);

      const int y0 = pInten_modifer_table[0];
      pDst[0].set(ir + y0, ig + y0, ib + y0);
      
      const int y1 = pInten_modifer_table[1];
      pDst[1].set(ir + y1, ig + y1, ib + y1);

      const int y2 = pInten_modifer_table[2];
      pDst[2].set(ir + y2, ig + y2, ib + y2);

      const int y3 = pInten_modifer_table[3];
      pDst[3].set(ir + y3, ig + y3, ib + y3);
   }
      
   bool unpack_etc1_block(const void* pETC1_block, unsigned int* pDst_pixels_rgba, bool preserve_alpha)
   {
      color_quad_u8* pDst = reinterpret_cast<color_quad_u8*>(pDst_pixels_rgba);
      const etc1_block& block = *static_cast<const etc1_block*>(pETC1_block);

      const bool diff_flag = block.get_diff_bit();
      const bool flip_flag = block.get_flip_bit();
      const uint table_index0 = block.get_inten_table(0);
      const uint table_index1 = block.get_inten_table(1);

      color_quad_u8 subblock_colors0[4];
      color_quad_u8 subblock_colors1[4];
      bool success = true;

      if (diff_flag)
      {
         const uint16 base_color5 = block.get_base5_color();
         const uint16 delta_color3 = block.get_delta3_color();
         etc1_block::get_diff_subblock_colors(subblock_colors0, base_color5, table_index0);
            
         if (!etc1_block::get_diff_subblock_colors(subblock_colors1, base_color5, delta_color3, table_index1))
            success = false;
      }
      else
      {
         const uint16 base_color4_0 = block.get_base4_color(0);
         etc1_block::get_abs_subblock_colors(subblock_colors0, base_color4_0, table_index0);

         const uint16 base_color4_1 = block.get_base4_color(1);
         etc1_block::get_abs_subblock_colors(subblock_colors1, base_color4_1, table_index1);
      }

      if (preserve_alpha)
      {
         if (flip_flag)
         {
            for (uint y = 0; y < 2; y++)
            {
               pDst[0].set_rgb(subblock_colors0[block.get_selector(0, y)]);
               pDst[1].set_rgb(subblock_colors0[block.get_selector(1, y)]);
               pDst[2].set_rgb(subblock_colors0[block.get_selector(2, y)]);
               pDst[3].set_rgb(subblock_colors0[block.get_selector(3, y)]);
               pDst += 4;
            }

            for (uint y = 2; y < 4; y++)
            {
               pDst[0].set_rgb(subblock_colors1[block.get_selector(0, y)]);
               pDst[1].set_rgb(subblock_colors1[block.get_selector(1, y)]);
               pDst[2].set_rgb(subblock_colors1[block.get_selector(2, y)]);
               pDst[3].set_rgb(subblock_colors1[block.get_selector(3, y)]);
               pDst += 4;
            }
         }
         else
         {
            for (uint y = 0; y < 4; y++)
            {
               pDst[0].set_rgb(subblock_colors0[block.get_selector(0, y)]);
               pDst[1].set_rgb(subblock_colors0[block.get_selector(1, y)]);
               pDst[2].set_rgb(subblock_colors1[block.get_selector(2, y)]);
               pDst[3].set_rgb(subblock_colors1[block.get_selector(3, y)]);
               pDst += 4;
            }
         }
      }
      else 
      {
         if (flip_flag)
         {
            // 0000
            // 0000
            // 1111
            // 1111
            for (uint y = 0; y < 2; y++)
            {
               pDst[0] = subblock_colors0[block.get_selector(0, y)];
               pDst[1] = subblock_colors0[block.get_selector(1, y)];
               pDst[2] = subblock_colors0[block.get_selector(2, y)];
               pDst[3] = subblock_colors0[block.get_selector(3, y)];
               pDst += 4;
            }

            for (uint y = 2; y < 4; y++)
            {
               pDst[0] = subblock_colors1[block.get_selector(0, y)];
               pDst[1] = subblock_colors1[block.get_selector(1, y)];
               pDst[2] = subblock_colors1[block.get_selector(2, y)];
               pDst[3] = subblock_colors1[block.get_selector(3, y)];
               pDst += 4;
            }
         }
         else
         {
            // 0011
            // 0011
            // 0011
            // 0011
            for (uint y = 0; y < 4; y++)
            {
               pDst[0] = subblock_colors0[block.get_selector(0, y)];
               pDst[1] = subblock_colors0[block.get_selector(1, y)];
               pDst[2] = subblock_colors1[block.get_selector(2, y)];
               pDst[3] = subblock_colors1[block.get_selector(3, y)];
               pDst += 4;
            }
         }
      }
      
      return success;
   }

   struct etc1_solution_coordinates
   {
      inline etc1_solution_coordinates() :
      m_unscaled_color(0, 0, 0, 0),
         m_inten_table(0),
         m_color4(false)
      {
      }

      inline etc1_solution_coordinates(uint r, uint g, uint b, uint inten_table, bool color4) : 
      m_unscaled_color(r, g, b, 255),
         m_inten_table(inten_table),
         m_color4(color4)
      {
      }

      inline etc1_solution_coordinates(const color_quad_u8& c, uint inten_table, bool color4) : 
      m_unscaled_color(c),
         m_inten_table(inten_table),
         m_color4(color4)
      {
      }

      inline etc1_solution_coordinates(const etc1_solution_coordinates& other)
      {
         *this = other;
      }

      inline etc1_solution_coordinates& operator= (const etc1_solution_coordinates& rhs)
      {
         m_unscaled_color = rhs.m_unscaled_color;
         m_inten_table = rhs.m_inten_table;
         m_color4 = rhs.m_color4;
         return *this;
      }

      inline void clear()
      {
         m_unscaled_color.clear();
         m_inten_table = 0;
         m_color4 = false;
      }

      inline color_quad_u8 get_scaled_color() const
      {
         int br, bg, bb;
         if (m_color4)
         {
            br = m_unscaled_color.r | (m_unscaled_color.r << 4);
            bg = m_unscaled_color.g | (m_unscaled_color.g << 4);
            bb = m_unscaled_color.b | (m_unscaled_color.b << 4);
         }
         else
         {
            br = (m_unscaled_color.r >> 2) | (m_unscaled_color.r << 3);
            bg = (m_unscaled_color.g >> 2) | (m_unscaled_color.g << 3);
            bb = (m_unscaled_color.b >> 2) | (m_unscaled_color.b << 3);
         }
         return color_quad_u8(br, bg, bb);
      }

      inline void get_block_colors(color_quad_u8* pBlock_colors)
      {
         int br, bg, bb;
         if (m_color4)
         {
            br = m_unscaled_color.r | (m_unscaled_color.r << 4);
            bg = m_unscaled_color.g | (m_unscaled_color.g << 4);
            bb = m_unscaled_color.b | (m_unscaled_color.b << 4);
         }
         else
         {
            br = (m_unscaled_color.r >> 2) | (m_unscaled_color.r << 3);
            bg = (m_unscaled_color.g >> 2) | (m_unscaled_color.g << 3);
            bb = (m_unscaled_color.b >> 2) | (m_unscaled_color.b << 3);
         }
         const int* pInten_table = g_etc1_inten_tables[m_inten_table];
         pBlock_colors[0].set(br + pInten_table[0], bg + pInten_table[0], bb + pInten_table[0]);
         pBlock_colors[1].set(br + pInten_table[1], bg + pInten_table[1], bb + pInten_table[1]);
         pBlock_colors[2].set(br + pInten_table[2], bg + pInten_table[2], bb + pInten_table[2]);
         pBlock_colors[3].set(br + pInten_table[3], bg + pInten_table[3], bb + pInten_table[3]);
      }

      color_quad_u8 m_unscaled_color;
      uint m_inten_table;
      bool m_color4;
   };

   class etc1_optimizer
   {
      etc1_optimizer(const etc1_optimizer&);
      etc1_optimizer& operator= (const etc1_optimizer&);

   public:
      etc1_optimizer()
      {
         clear();
      }

      void clear()
      {
         m_pParams = NULL;
         m_pResult = NULL;
         m_pSorted_luma = NULL;
         m_pSorted_luma_indices = NULL;
      }

      struct params : etc1_pack_params
      {
         params()
         {
            clear();
         }

         params(const etc1_pack_params& base_params) : 
         etc1_pack_params(base_params)
         {
            clear_optimizer_params();
         }

         void clear()
         {
            etc1_pack_params::clear();
            clear_optimizer_params();
         }

         void clear_optimizer_params()
         {
            m_num_src_pixels = 0;
            m_pSrc_pixels = 0;

            m_use_color4 = false;
            static const int s_default_scan_delta[] = { 0 };
            m_pScan_deltas = s_default_scan_delta;
            m_scan_delta_size = 1;

            m_base_color5.clear();
            m_constrain_against_base_color5 = false;
         }

         uint m_num_src_pixels;
         const color_quad_u8* m_pSrc_pixels;

         bool m_use_color4;
         const int* m_pScan_deltas;
         uint m_scan_delta_size;

         color_quad_u8 m_base_color5;
         bool m_constrain_against_base_color5;
      };

      struct results
      {
         uint64 m_error;
         color_quad_u8 m_block_color_unscaled;
         uint m_block_inten_table;
         uint m_n;
         uint8* m_pSelectors;
         bool m_block_color4;

         inline results& operator= (const results& rhs)
         {
            m_block_color_unscaled = rhs.m_block_color_unscaled;
            m_block_color4 = rhs.m_block_color4;
            m_block_inten_table = rhs.m_block_inten_table;
            m_error = rhs.m_error;
            RG_ETC1_ASSERT(m_n == rhs.m_n);
            memcpy(m_pSelectors, rhs.m_pSelectors, rhs.m_n);
            return *this;
         }
      };

      void init(const params& params, results& result);
      bool compute();

   private:      
      struct potential_solution
      {
         potential_solution() : m_coords(), m_error(cUINT64_MAX), m_valid(false)
         {
         }

         etc1_solution_coordinates  m_coords;
         uint8                      m_selectors[8];
         uint64                     m_error;
         bool                       m_valid;

         void clear()
         {
            m_coords.clear();
            m_error = cUINT64_MAX;
            m_valid = false;
         }
      };

      const params* m_pParams;
      results* m_pResult;

      int m_limit;

      vec3F m_avg_color;
      int m_br, m_bg, m_bb;
      uint16 m_luma[8];
      uint32 m_sorted_luma[2][8];
      const uint32* m_pSorted_luma_indices;
      uint32* m_pSorted_luma;

      uint8 m_selectors[8];
      uint8 m_best_selectors[8];

      potential_solution m_best_solution;
      potential_solution m_trial_solution;
      uint8 m_temp_selectors[8];

      bool evaluate_solution(const etc1_solution_coordinates& coords, potential_solution& trial_solution, potential_solution* pBest_solution);
      bool evaluate_solution_fast(const etc1_solution_coordinates& coords, potential_solution& trial_solution, potential_solution* pBest_solution);
   };
      
   bool etc1_optimizer::compute()
   {
      const uint n = m_pParams->m_num_src_pixels;
      const int scan_delta_size = m_pParams->m_scan_delta_size;
      
      // Scan through a subset of the 3D lattice centered around the avg block color trying each 3D (555 or 444) lattice point as a potential block color.
      // Each time a better solution is found try to refine the current solution's block color based of the current selectors and intensity table index.
      for (int zdi = 0; zdi < scan_delta_size; zdi++)
      {
         const int zd = m_pParams->m_pScan_deltas[zdi];
         const int mbb = m_bb + zd;
         if (mbb < 0) continue; else if (mbb > m_limit) break;
         
         for (int ydi = 0; ydi < scan_delta_size; ydi++)
         {
            const int yd = m_pParams->m_pScan_deltas[ydi];
            const int mbg = m_bg + yd;
            if (mbg < 0) continue; else if (mbg > m_limit) break;

            for (int xdi = 0; xdi < scan_delta_size; xdi++)
            {
               const int xd = m_pParams->m_pScan_deltas[xdi];
               const int mbr = m_br + xd;
               if (mbr < 0) continue; else if (mbr > m_limit) break;
      
               etc1_solution_coordinates coords(mbr, mbg, mbb, 0, m_pParams->m_use_color4);
               if (m_pParams->m_quality == cHighQuality)
               {
                  if (!evaluate_solution(coords, m_trial_solution, &m_best_solution))
                     continue;
               }
               else
               {
                  if (!evaluate_solution_fast(coords, m_trial_solution, &m_best_solution))
                     continue;
               }
               
               // Now we have the input block, the avg. color of the input pixels, a set of trial selector indices, and the block color+intensity index.
               // Now, for each component, attempt to refine the current solution by solving a simple linear equation. For example, for 4 colors:
               // The goal is:
               // pixel0 - (block_color+inten_table[selector0]) + pixel1 - (block_color+inten_table[selector1]) + pixel2 - (block_color+inten_table[selector2]) + pixel3 - (block_color+inten_table[selector3]) = 0
               // Rearranging this:
               // (pixel0 + pixel1 + pixel2 + pixel3) - (block_color+inten_table[selector0]) - (block_color+inten_table[selector1]) - (block_color+inten_table[selector2]) - (block_color+inten_table[selector3]) = 0
               // (pixel0 + pixel1 + pixel2 + pixel3) - block_color - inten_table[selector0] - block_color-inten_table[selector1] - block_color-inten_table[selector2] - block_color-inten_table[selector3] = 0
               // (pixel0 + pixel1 + pixel2 + pixel3) - 4*block_color - inten_table[selector0] - inten_table[selector1] - inten_table[selector2] - inten_table[selector3] = 0
               // (pixel0 + pixel1 + pixel2 + pixel3) - 4*block_color - (inten_table[selector0] + inten_table[selector1] + inten_table[selector2] + inten_table[selector3]) = 0
               // (pixel0 + pixel1 + pixel2 + pixel3)/4 - block_color - (inten_table[selector0] + inten_table[selector1] + inten_table[selector2] + inten_table[selector3])/4 = 0
               // block_color = (pixel0 + pixel1 + pixel2 + pixel3)/4 - (inten_table[selector0] + inten_table[selector1] + inten_table[selector2] + inten_table[selector3])/4
               // So what this means:
               // optimal_block_color = avg_input - avg_inten_delta
               // So the optimal block color can be computed by taking the average block color and subtracting the current average of the intensity delta.
               // Unfortunately, optimal_block_color must then be quantized to 555 or 444 so it's not always possible to improve matters using this formula.
               // Also, the above formula is for unclamped intensity deltas. The actual implementation takes into account clamping.

               const uint max_refinement_trials = (m_pParams->m_quality == cLowQuality) ? 2 : (((xd | yd | zd) == 0) ? 4 : 2);
               for (uint refinement_trial = 0; refinement_trial < max_refinement_trials; refinement_trial++)
               {
                  const uint8* pSelectors = m_best_solution.m_selectors;
                  const int* pInten_table = g_etc1_inten_tables[m_best_solution.m_coords.m_inten_table];

                  int delta_sum_r = 0, delta_sum_g = 0, delta_sum_b = 0;
                  const color_quad_u8 base_color(m_best_solution.m_coords.get_scaled_color());
                  for (uint r = 0; r < n; r++)
                  {
                     const uint s = *pSelectors++;
                     const int yd = pInten_table[s];
                     // Compute actual delta being applied to each pixel, taking into account clamping.
                     delta_sum_r += rg_etc1::clamp<int>(base_color.r + yd, 0, 255) - base_color.r;
                     delta_sum_g += rg_etc1::clamp<int>(base_color.g + yd, 0, 255) - base_color.g;
                     delta_sum_b += rg_etc1::clamp<int>(base_color.b + yd, 0, 255) - base_color.b;
                  }
                  if ((!delta_sum_r) && (!delta_sum_g) && (!delta_sum_b))
                     break;
                  const float avg_delta_r_f = static_cast<float>(delta_sum_r) / n;
                  const float avg_delta_g_f = static_cast<float>(delta_sum_g) / n;
                  const float avg_delta_b_f = static_cast<float>(delta_sum_b) / n;
                  const int br1 = rg_etc1::clamp<int>(static_cast<uint>((m_avg_color[0] - avg_delta_r_f) * m_limit / 255.0f + .5f), 0, m_limit);
                  const int bg1 = rg_etc1::clamp<int>(static_cast<uint>((m_avg_color[1] - avg_delta_g_f) * m_limit / 255.0f + .5f), 0, m_limit);
                  const int bb1 = rg_etc1::clamp<int>(static_cast<uint>((m_avg_color[2] - avg_delta_b_f) * m_limit / 255.0f + .5f), 0, m_limit);
                  
                  bool skip = false;
                  
                  if ((mbr == br1) && (mbg == bg1) && (mbb == bb1))
                     skip = true;
                  else if ((br1 == m_best_solution.m_coords.m_unscaled_color.r) && (bg1 == m_best_solution.m_coords.m_unscaled_color.g) && (bb1 == m_best_solution.m_coords.m_unscaled_color.b))
                     skip = true;
                  else if ((m_br == br1) && (m_bg == bg1) && (m_bb == bb1))
                     skip = true;

                  if (skip)
                     break;

                  etc1_solution_coordinates coords1(br1, bg1, bb1, 0, m_pParams->m_use_color4);
                  if (m_pParams->m_quality == cHighQuality)
                  {
                     if (!evaluate_solution(coords1, m_trial_solution, &m_best_solution)) 
                        break;
                  }
                  else
                  {
                     if (!evaluate_solution_fast(coords1, m_trial_solution, &m_best_solution))
                        break;
                  }

               }  // refinement_trial

            } // xdi
         } // ydi
      } // zdi

      if (!m_best_solution.m_valid)
      {
         m_pResult->m_error = cUINT32_MAX;
         return false;
      }
      
      const uint8* pSelectors = m_best_solution.m_selectors;

#ifdef RG_ETC1_BUILD_DEBUG
      {
         color_quad_u8 block_colors[4];
         m_best_solution.m_coords.get_block_colors(block_colors);

         const color_quad_u8* pSrc_pixels = m_pParams->m_pSrc_pixels;
         uint64 actual_error = 0;
         for (uint i = 0; i < n; i++)
            actual_error += pSrc_pixels[i].squared_distance_rgb(block_colors[pSelectors[i]]);
         
         RG_ETC1_ASSERT(actual_error == m_best_solution.m_error);
      }
#endif      
      
      m_pResult->m_error = m_best_solution.m_error;

      m_pResult->m_block_color_unscaled = m_best_solution.m_coords.m_unscaled_color;
      m_pResult->m_block_color4 = m_best_solution.m_coords.m_color4;
      
      m_pResult->m_block_inten_table = m_best_solution.m_coords.m_inten_table;
      memcpy(m_pResult->m_pSelectors, pSelectors, n);
      m_pResult->m_n = n;

      return true;
   }

   void etc1_optimizer::init(const params& p, results& r)
   {
      // This version is hardcoded for 8 pixel subblocks.
      RG_ETC1_ASSERT(p.m_num_src_pixels == 8);
      
      m_pParams = &p;
      m_pResult = &r;
                  
      const uint n = 8;
      
      m_limit = m_pParams->m_use_color4 ? 15 : 31;

      vec3F avg_color(0.0f);

      for (uint i = 0; i < n; i++)
      {
         const color_quad_u8& c = m_pParams->m_pSrc_pixels[i];
         const vec3F fc(c.r, c.g, c.b);

         avg_color += fc;

         m_luma[i] = static_cast<uint16>(c.r + c.g + c.b);
         m_sorted_luma[0][i] = i;
      }
      avg_color *= (1.0f / static_cast<float>(n));
      m_avg_color = avg_color;

      m_br = rg_etc1::clamp<int>(static_cast<uint>(m_avg_color[0] * m_limit / 255.0f + .5f), 0, m_limit);
      m_bg = rg_etc1::clamp<int>(static_cast<uint>(m_avg_color[1] * m_limit / 255.0f + .5f), 0, m_limit);
      m_bb = rg_etc1::clamp<int>(static_cast<uint>(m_avg_color[2] * m_limit / 255.0f + .5f), 0, m_limit);

      if (m_pParams->m_quality <= cMediumQuality)
      {
         m_pSorted_luma_indices = indirect_radix_sort(n, m_sorted_luma[0], m_sorted_luma[1], m_luma, 0, sizeof(m_luma[0]), false);
         m_pSorted_luma = m_sorted_luma[0];
         if (m_pSorted_luma_indices == m_sorted_luma[0])
            m_pSorted_luma = m_sorted_luma[1];
      
         for (uint i = 0; i < n; i++)
            m_pSorted_luma[i] = m_luma[m_pSorted_luma_indices[i]];
      }
      
      m_best_solution.m_coords.clear();
      m_best_solution.m_valid = false;
      m_best_solution.m_error = cUINT64_MAX;
   }

   bool etc1_optimizer::evaluate_solution(const etc1_solution_coordinates& coords, potential_solution& trial_solution, potential_solution* pBest_solution)
   {
      trial_solution.m_valid = false;

      if (m_pParams->m_constrain_against_base_color5)
      {
         const int dr = coords.m_unscaled_color.r - m_pParams->m_base_color5.r;
         const int dg = coords.m_unscaled_color.g - m_pParams->m_base_color5.g;
         const int db = coords.m_unscaled_color.b - m_pParams->m_base_color5.b;

         if ((rg_etc1::minimum(dr, dg, db) < cETC1ColorDeltaMin) || (rg_etc1::maximum(dr, dg, db) > cETC1ColorDeltaMax))
            return false;
      }

      const color_quad_u8 base_color(coords.get_scaled_color());
      
      const uint n = 8;
            
      trial_solution.m_error = cUINT64_MAX;
            
      for (uint inten_table = 0; inten_table < cETC1IntenModifierValues; inten_table++)
      {
         const int* pInten_table = g_etc1_inten_tables[inten_table];

         color_quad_u8 block_colors[4];
         for (uint s = 0; s < 4; s++)
         {
            const int yd = pInten_table[s];
            block_colors[s].set(base_color.r + yd, base_color.g + yd, base_color.b + yd, 0);
         }
         
         uint64 total_error = 0;
         
         const color_quad_u8* pSrc_pixels = m_pParams->m_pSrc_pixels;
         for (uint c = 0; c < n; c++)
         {
            const color_quad_u8& src_pixel = *pSrc_pixels++;
            
            uint best_selector_index = 0;
            uint best_error = rg_etc1::square(src_pixel.r - block_colors[0].r) + rg_etc1::square(src_pixel.g - block_colors[0].g) + rg_etc1::square(src_pixel.b - block_colors[0].b);

            uint trial_error = rg_etc1::square(src_pixel.r - block_colors[1].r) + rg_etc1::square(src_pixel.g - block_colors[1].g) + rg_etc1::square(src_pixel.b - block_colors[1].b);
            if (trial_error < best_error)
            {
               best_error = trial_error;
               best_selector_index = 1;
            }

            trial_error = rg_etc1::square(src_pixel.r - block_colors[2].r) + rg_etc1::square(src_pixel.g - block_colors[2].g) + rg_etc1::square(src_pixel.b - block_colors[2].b);
            if (trial_error < best_error)
            {
               best_error = trial_error;
               best_selector_index = 2;
            }

            trial_error = rg_etc1::square(src_pixel.r - block_colors[3].r) + rg_etc1::square(src_pixel.g - block_colors[3].g) + rg_etc1::square(src_pixel.b - block_colors[3].b);
            if (trial_error < best_error)
            {
               best_error = trial_error;
               best_selector_index = 3;
            }

            m_temp_selectors[c] = static_cast<uint8>(best_selector_index);

            total_error += best_error;
            if (total_error >= trial_solution.m_error)
               break;
         }
         
         if (total_error < trial_solution.m_error)
         {
            trial_solution.m_error = total_error;
            trial_solution.m_coords.m_inten_table = inten_table;
            memcpy(trial_solution.m_selectors, m_temp_selectors, 8);
            trial_solution.m_valid = true;
         }
      }
      trial_solution.m_coords.m_unscaled_color = coords.m_unscaled_color;
      trial_solution.m_coords.m_color4 = m_pParams->m_use_color4;

      bool success = false;
      if (pBest_solution)
      {
         if (trial_solution.m_error < pBest_solution->m_error)
         {
            *pBest_solution = trial_solution;
            success = true;
         }
      }

      return success;
   }

   bool etc1_optimizer::evaluate_solution_fast(const etc1_solution_coordinates& coords, potential_solution& trial_solution, potential_solution* pBest_solution)
   {
      if (m_pParams->m_constrain_against_base_color5)
      {
         const int dr = coords.m_unscaled_color.r - m_pParams->m_base_color5.r;
         const int dg = coords.m_unscaled_color.g - m_pParams->m_base_color5.g;
         const int db = coords.m_unscaled_color.b - m_pParams->m_base_color5.b;

         if ((rg_etc1::minimum(dr, dg, db) < cETC1ColorDeltaMin) || (rg_etc1::maximum(dr, dg, db) > cETC1ColorDeltaMax))
         {
            trial_solution.m_valid = false;
            return false;
         }
      }

      const color_quad_u8 base_color(coords.get_scaled_color());

      const uint n = 8;
      
      trial_solution.m_error = cUINT64_MAX;

      for (int inten_table = cETC1IntenModifierValues - 1; inten_table >= 0; --inten_table)
      {
         const int* pInten_table = g_etc1_inten_tables[inten_table];

         uint block_inten[4];
         color_quad_u8 block_colors[4];
         for (uint s = 0; s < 4; s++)
         {
            const int yd = pInten_table[s];
            color_quad_u8 block_color(base_color.r + yd, base_color.g + yd, base_color.b + yd, 0);
            block_colors[s] = block_color;
            block_inten[s] = block_color.r + block_color.g + block_color.b;
         }

         // evaluate_solution_fast() enforces/assumesd a total ordering of the input colors along the intensity (1,1,1) axis to more quickly classify the inputs to selectors.
         // The inputs colors have been presorted along the projection onto this axis, and ETC1 block colors are always ordered along the intensity axis, so this classification is fast.
         // 0   1   2   3
         //   01  12  23
         const uint block_inten_midpoints[3] = { block_inten[0] + block_inten[1], block_inten[1] + block_inten[2], block_inten[2] + block_inten[3] };

         uint64 total_error = 0;
         const color_quad_u8* pSrc_pixels = m_pParams->m_pSrc_pixels;
         if ((m_pSorted_luma[n - 1] * 2) < block_inten_midpoints[0])
         {
            if (block_inten[0] > m_pSorted_luma[n - 1])
            {
               const uint min_error = labs(block_inten[0] - m_pSorted_luma[n - 1]);
               if (min_error >= trial_solution.m_error)
                  continue;
            }

            memset(&m_temp_selectors[0], 0, n);

            for (uint c = 0; c < n; c++)
               total_error += block_colors[0].squared_distance_rgb(pSrc_pixels[c]);
         }
         else if ((m_pSorted_luma[0] * 2) >= block_inten_midpoints[2])
         {
            if (m_pSorted_luma[0] > block_inten[3])
            {
               const uint min_error = labs(m_pSorted_luma[0] - block_inten[3]);
               if (min_error >= trial_solution.m_error)
                  continue;
            }

            memset(&m_temp_selectors[0], 3, n);

            for (uint c = 0; c < n; c++)
               total_error += block_colors[3].squared_distance_rgb(pSrc_pixels[c]);
         }
         else
         {
            uint cur_selector = 0, c;
            for (c = 0; c < n; c++)
            {
               const uint y = m_pSorted_luma[c];
               while ((y * 2) >= block_inten_midpoints[cur_selector])
                  if (++cur_selector > 2)
                     goto done;
               const uint sorted_pixel_index = m_pSorted_luma_indices[c];
               m_temp_selectors[sorted_pixel_index] = static_cast<uint8>(cur_selector);
               total_error += block_colors[cur_selector].squared_distance_rgb(pSrc_pixels[sorted_pixel_index]);
            }
done:
            while (c < n)
            {
               const uint sorted_pixel_index = m_pSorted_luma_indices[c];
               m_temp_selectors[sorted_pixel_index] = 3;
               total_error += block_colors[3].squared_distance_rgb(pSrc_pixels[sorted_pixel_index]);
               ++c;
            }
         }

         if (total_error < trial_solution.m_error)
         {
            trial_solution.m_error = total_error;
            trial_solution.m_coords.m_inten_table = inten_table;
            memcpy(trial_solution.m_selectors, m_temp_selectors, n);
            trial_solution.m_valid = true;
            if (!total_error)
               break;
         }
      }
      trial_solution.m_coords.m_unscaled_color = coords.m_unscaled_color;
      trial_solution.m_coords.m_color4 = m_pParams->m_use_color4;
      
      bool success = false;
      if (pBest_solution)
      {
         if (trial_solution.m_error < pBest_solution->m_error)
         {
            *pBest_solution = trial_solution;
            success = true;
         }
      }

      return success;
   }
         
   static uint etc1_decode_value(uint diff, uint inten, uint selector, uint packed_c)
   {
      const uint limit = diff ? 32 : 16; limit;
      RG_ETC1_ASSERT((diff < 2) && (inten < 8) && (selector < 4) && (packed_c < limit));
      int c;
      if (diff)
         c = (packed_c >> 2) | (packed_c << 3);
      else 
         c = packed_c | (packed_c << 4);
      c += g_etc1_inten_tables[inten][selector];
      c = rg_etc1::clamp<int>(c, 0, 255);
      return c;
   }

   static inline int mul_8bit(int a, int b) { int t = a*b + 128; return (t + (t >> 8)) >> 8; }

   void pack_etc1_block_init()
   {
      for (uint diff = 0; diff < 2; diff++)
      {
         const uint limit = diff ? 32 : 16;

         for (uint inten = 0; inten < 8; inten++)
         {
            for (uint selector = 0; selector < 4; selector++)
            {
               const uint inverse_table_index = diff + (inten << 1) + (selector << 4);
               for (uint color = 0; color < 256; color++)
               {
                  uint best_error = cUINT32_MAX, best_packed_c = 0;
                  for (uint packed_c = 0; packed_c < limit; packed_c++)
                  {
                     int v = etc1_decode_value(diff, inten, selector, packed_c);
                     uint err = labs(v - static_cast<int>(color));
                     if (err < best_error)
                     {
                        best_error = err;
                        best_packed_c = packed_c;
                        if (!best_error) 
                           break;
                     }
                  }
                  RG_ETC1_ASSERT(best_error <= 255);
                  g_etc1_inverse_lookup[inverse_table_index][color] = static_cast<uint16>(best_packed_c | (best_error << 8));
               }
            }
         }
      }
      
      uint expand5[32];
      for(int i = 0; i < 32; i++)
         expand5[i] = (i << 3) | (i >> 2);

      for(int i = 0; i < 256 + 16; i++)
      {
         int v = clamp<int>(i - 8, 0, 255);
         g_quant5_tab[i] = static_cast<uint8>(expand5[mul_8bit(v,31)]);
      }
   }

   // Packs solid color blocks efficiently using a set of small precomputed tables.
   // For random 888 inputs, MSE results are better than Erricson's ETC1 packer in "slow" mode ~9.5% of the time, is slightly worse only ~.01% of the time, and is equal the rest of the time.
   static uint64 pack_etc1_block_solid_color(etc1_block& block, const uint8* pColor, etc1_pack_params& pack_params)
   {
      pack_params;
      RG_ETC1_ASSERT(g_etc1_inverse_lookup[0][255]);
            
      static uint s_next_comp[4] = { 1, 2, 0, 1 };
            
      uint best_error = cUINT32_MAX, best_i = 0;
      int best_x = 0, best_packed_c1 = 0, best_packed_c2 = 0;

      // For each possible 8-bit value, there is a precomputed list of diff/inten/selector configurations that allow that 8-bit value to be encoded with no error.
      for (uint i = 0; i < 3; i++)
      {
         const uint c1 = pColor[s_next_comp[i]], c2 = pColor[s_next_comp[i + 1]];

         const int delta_range = 1;
         for (int delta = -delta_range; delta <= delta_range; delta++)
         {
            const int c_plus_delta = rg_etc1::clamp<int>(pColor[i] + delta, 0, 255);

            const uint16* pTable;
            if (!c_plus_delta)
               pTable = g_color8_to_etc_block_config_0_255[0];
            else if (c_plus_delta == 255)
               pTable = g_color8_to_etc_block_config_0_255[1];
            else
               pTable = g_color8_to_etc_block_config_1_to_254[c_plus_delta - 1];

            do
            {
               const uint x = *pTable++;

#ifdef RG_ETC1_BUILD_DEBUG
               const uint diff = x & 1;
               const uint inten = (x >> 1) & 7;
               const uint selector = (x >> 4) & 3;
               const uint p0 = (x >> 8) & 255;
               RG_ETC1_ASSERT(etc1_decode_value(diff, inten, selector, p0) == (uint)c_plus_delta);
#endif

               const uint16* pInverse_table = g_etc1_inverse_lookup[x & 0xFF];
               uint16 p1 = pInverse_table[c1];
               uint16 p2 = pInverse_table[c2];
               const uint trial_error = rg_etc1::square(c_plus_delta - pColor[i]) + rg_etc1::square(p1 >> 8) + rg_etc1::square(p2 >> 8);
               if (trial_error < best_error)
               {
                  best_error = trial_error;
                  best_x = x;
                  best_packed_c1 = p1 & 0xFF;
                  best_packed_c2 = p2 & 0xFF;
                  best_i = i;
                  if (!best_error)
                     goto found_perfect_match;
               }
            } while (*pTable != 0xFFFF);
         }
      }
found_perfect_match:

      const uint diff = best_x & 1;
      const uint inten = (best_x >> 1) & 7;

      block.m_bytes[3] = static_cast<uint8>(((inten | (inten << 3)) << 2) | (diff << 1));
                        
      const uint etc1_selector = g_selector_index_to_etc1[(best_x >> 4) & 3];
      *reinterpret_cast<uint16*>(&block.m_bytes[4]) = (etc1_selector & 2) ? 0xFFFF : 0;
      *reinterpret_cast<uint16*>(&block.m_bytes[6]) = (etc1_selector & 1) ? 0xFFFF : 0;

      const uint best_packed_c0 = (best_x >> 8) & 255;
      if (diff)
      {
         block.m_bytes[best_i] = static_cast<uint8>(best_packed_c0 << 3);
         block.m_bytes[s_next_comp[best_i]] = static_cast<uint8>(best_packed_c1 << 3);
         block.m_bytes[s_next_comp[best_i+1]] = static_cast<uint8>(best_packed_c2 << 3);
      }
      else
      {
         block.m_bytes[best_i] = static_cast<uint8>(best_packed_c0 | (best_packed_c0 << 4));
         block.m_bytes[s_next_comp[best_i]] = static_cast<uint8>(best_packed_c1 | (best_packed_c1 << 4));
         block.m_bytes[s_next_comp[best_i+1]] = static_cast<uint8>(best_packed_c2 | (best_packed_c2 << 4));
      }

      return best_error;
   }
      
   static uint pack_etc1_block_solid_color_constrained(
      etc1_optimizer::results& results, 
      uint num_colors, const uint8* pColor, 
      etc1_pack_params& pack_params, 
      bool use_diff,
      const color_quad_u8* pBase_color5_unscaled)
   {
      RG_ETC1_ASSERT(g_etc1_inverse_lookup[0][255]);

      pack_params;
      static uint s_next_comp[4] = { 1, 2, 0, 1 };

      uint best_error = cUINT32_MAX, best_i = 0;
      int best_x = 0, best_packed_c1 = 0, best_packed_c2 = 0;

      // For each possible 8-bit value, there is a precomputed list of diff/inten/selector configurations that allow that 8-bit value to be encoded with no error.
      for (uint i = 0; i < 3; i++)
      {
         const uint c1 = pColor[s_next_comp[i]], c2 = pColor[s_next_comp[i + 1]];

         const int delta_range = 1;
         for (int delta = -delta_range; delta <= delta_range; delta++)
         {
            const int c_plus_delta = rg_etc1::clamp<int>(pColor[i] + delta, 0, 255);

            const uint16* pTable;
            if (!c_plus_delta)
               pTable = g_color8_to_etc_block_config_0_255[0];
            else if (c_plus_delta == 255)
               pTable = g_color8_to_etc_block_config_0_255[1];
            else
               pTable = g_color8_to_etc_block_config_1_to_254[c_plus_delta - 1];

            do
            {
               const uint x = *pTable++;
               const uint diff = x & 1;
               if (static_cast<uint>(use_diff) != diff)
               {
                  if (*pTable == 0xFFFF)
                     break;
                  continue;
               }

               if ((diff) && (pBase_color5_unscaled))
               {
                  const int p0 = (x >> 8) & 255;
                  int delta = p0 - static_cast<int>(pBase_color5_unscaled->c[i]);
                  if ((delta < cETC1ColorDeltaMin) || (delta > cETC1ColorDeltaMax))
                  {
                     if (*pTable == 0xFFFF)
                        break;
                     continue;
                  }
               }

#ifdef RG_ETC1_BUILD_DEBUG
               {
                  const uint inten = (x >> 1) & 7;
                  const uint selector = (x >> 4) & 3;
                  const uint p0 = (x >> 8) & 255;
                  RG_ETC1_ASSERT(etc1_decode_value(diff, inten, selector, p0) == (uint)c_plus_delta);
               }
#endif

               const uint16* pInverse_table = g_etc1_inverse_lookup[x & 0xFF];
               uint16 p1 = pInverse_table[c1];
               uint16 p2 = pInverse_table[c2];

               if ((diff) && (pBase_color5_unscaled))
               {
                  int delta1 = (p1 & 0xFF) - static_cast<int>(pBase_color5_unscaled->c[s_next_comp[i]]);
                  int delta2 = (p2 & 0xFF) - static_cast<int>(pBase_color5_unscaled->c[s_next_comp[i + 1]]);
                  if ((delta1 < cETC1ColorDeltaMin) || (delta1 > cETC1ColorDeltaMax) || (delta2 < cETC1ColorDeltaMin) || (delta2 > cETC1ColorDeltaMax))
                  {
                     if (*pTable == 0xFFFF)
                        break;
                     continue;
                  }
               }

               const uint trial_error = rg_etc1::square(c_plus_delta - pColor[i]) + rg_etc1::square(p1 >> 8) + rg_etc1::square(p2 >> 8);
               if (trial_error < best_error)
               {
                  best_error = trial_error;
                  best_x = x;
                  best_packed_c1 = p1 & 0xFF;
                  best_packed_c2 = p2 & 0xFF;
                  best_i = i;
                  if (!best_error)
                     goto found_perfect_match;
               }
            } while (*pTable != 0xFFFF);
         }
      }
found_perfect_match:

      if (best_error == cUINT32_MAX)
         return best_error;

      best_error *= num_colors;

      results.m_n = num_colors;
      results.m_block_color4 = !(best_x & 1);
      results.m_block_inten_table = (best_x >> 1) & 7;
      memset(results.m_pSelectors, (best_x >> 4) & 3, num_colors);

      const uint best_packed_c0 = (best_x >> 8) & 255;
      results.m_block_color_unscaled[best_i] = static_cast<uint8>(best_packed_c0);
      results.m_block_color_unscaled[s_next_comp[best_i]] = static_cast<uint8>(best_packed_c1);
      results.m_block_color_unscaled[s_next_comp[best_i + 1]] = static_cast<uint8>(best_packed_c2);
      results.m_error = best_error;
      
      return best_error;
   }

   // Function originally from RYG's public domain real-time DXT1 compressor, modified for 555.
   static void dither_block_555(color_quad_u8* dest, const color_quad_u8* block)
   {
      int err[8],*ep1 = err,*ep2 = err+4;
      uint8 *quant = g_quant5_tab+8;

      memset(dest, 0xFF, sizeof(color_quad_u8)*16);

      // process channels seperately
      for(int ch=0;ch<3;ch++)
      {
         uint8* bp = (uint8*)block;
         uint8* dp = (uint8*)dest;

         bp += ch; dp += ch;

         memset(err,0, sizeof(err));
         for(int y = 0; y < 4; y++)
         {
            // pixel 0
            dp[ 0] = quant[bp[ 0] + ((3*ep2[1] + 5*ep2[0]) >> 4)];
            ep1[0] = bp[ 0] - dp[ 0];

            // pixel 1
            dp[ 4] = quant[bp[ 4] + ((7*ep1[0] + 3*ep2[2] + 5*ep2[1] + ep2[0]) >> 4)];
            ep1[1] = bp[ 4] - dp[ 4];

            // pixel 2
            dp[ 8] = quant[bp[ 8] + ((7*ep1[1] + 3*ep2[3] + 5*ep2[2] + ep2[1]) >> 4)];
            ep1[2] = bp[ 8] - dp[ 8];

            // pixel 3
            dp[12] = quant[bp[12] + ((7*ep1[2] + 5*ep2[3] + ep2[2]) >> 4)];
            ep1[3] = bp[12] - dp[12];

            // advance to next line
            int* tmp = ep1; ep1 = ep2; ep2 = tmp;
            bp += 16;
            dp += 16;
         }
      }
   }

   unsigned int pack_etc1_block(void* pETC1_block, const unsigned int* pSrc_pixels_rgba, etc1_pack_params& pack_params)
   {
      const color_quad_u8* pSrc_pixels = reinterpret_cast<const color_quad_u8*>(pSrc_pixels_rgba);
      etc1_block& dst_block = *static_cast<etc1_block*>(pETC1_block);

#ifdef RG_ETC1_BUILD_DEBUG
      // Ensure all alpha values are 0xFF.
      for (uint i = 0; i < 16; i++)
      {
         RG_ETC1_ASSERT(pSrc_pixels[i].a == 255);
      }
#endif

      color_quad_u8 src_pixel0(pSrc_pixels[0]);

      // Check for solid block.
      const uint32 first_pixel_u32 = pSrc_pixels->m_u32;
      int r;
      for (r = 15; r >= 1; --r)
         if (pSrc_pixels[r].m_u32 != first_pixel_u32)
            break;
      if (!r)
         return static_cast<unsigned int>(16 * pack_etc1_block_solid_color(dst_block, &pSrc_pixels[0].r, pack_params));
      
      color_quad_u8 dithered_pixels[16];
      if (pack_params.m_dithering)
      {
         dither_block_555(dithered_pixels, pSrc_pixels);
         pSrc_pixels = dithered_pixels;
      }

      etc1_optimizer optimizer;

      uint64 best_error = cUINT64_MAX;
      uint best_flip = false, best_use_color4 = false;
      
      uint8 best_selectors[2][8];
      etc1_optimizer::results best_results[2];
      for (uint i = 0; i < 2; i++)
      {
         best_results[i].m_n = 8;
         best_results[i].m_pSelectors = best_selectors[i];
      }
      
      uint8 selectors[3][8];
      etc1_optimizer::results results[3];
      
      for (uint i = 0; i < 3; i++)
      {
         results[i].m_n = 8;
         results[i].m_pSelectors = selectors[i];
      }
            
      color_quad_u8 subblock_pixels[8];

      etc1_optimizer::params params(pack_params);
      params.m_num_src_pixels = 8;
      params.m_pSrc_pixels = subblock_pixels;

      for (uint flip = 0; flip < 2; flip++)
      {
         for (uint use_color4 = 0; use_color4 < 2; use_color4++)
         {
            uint64 trial_error = 0;

            uint subblock;
            for (subblock = 0; subblock < 2; subblock++)
            {
               if (flip)
                  memcpy(subblock_pixels, pSrc_pixels + subblock * 8, sizeof(color_quad_u8) * 8);
               else
               {
                  const color_quad_u8* pSrc_col = pSrc_pixels + subblock * 2;
                  subblock_pixels[0] = pSrc_col[0]; subblock_pixels[1] = pSrc_col[4]; subblock_pixels[2] = pSrc_col[8]; subblock_pixels[3] = pSrc_col[12];
                  subblock_pixels[4] = pSrc_col[1]; subblock_pixels[5] = pSrc_col[5]; subblock_pixels[6] = pSrc_col[9]; subblock_pixels[7] = pSrc_col[13];
               }

               results[2].m_error = cUINT64_MAX;
               if ((params.m_quality >= cMediumQuality) && ((subblock) || (use_color4)))
               {
                  const uint32 subblock_pixel0_u32 = subblock_pixels[0].m_u32;
                  for (r = 7; r >= 1; --r)
                     if (subblock_pixels[r].m_u32 != subblock_pixel0_u32)
                        break;
                  if (!r)
                  {
                     pack_etc1_block_solid_color_constrained(results[2], 8, &subblock_pixels[0].r, pack_params, !use_color4, (subblock && !use_color4) ? &results[0].m_block_color_unscaled : NULL);
                  }
               }

               params.m_use_color4 = (use_color4 != 0);
               params.m_constrain_against_base_color5 = false;

               if ((!use_color4) && (subblock))
               {
                  params.m_constrain_against_base_color5 = true;
                  params.m_base_color5 = results[0].m_block_color_unscaled;
               }
                              
               if (params.m_quality == cHighQuality)
               {
                  static const int s_scan_delta_0_to_4[] = { -4, -3, -2, -1, 0, 1, 2, 3, 4 };
                  params.m_scan_delta_size = RG_ETC1_ARRAY_SIZE(s_scan_delta_0_to_4);
                  params.m_pScan_deltas = s_scan_delta_0_to_4;
               }
               else if (params.m_quality == cMediumQuality)
               {
                  static const int s_scan_delta_0_to_1[] = { -1, 0, 1 };
                  params.m_scan_delta_size = RG_ETC1_ARRAY_SIZE(s_scan_delta_0_to_1);
                  params.m_pScan_deltas = s_scan_delta_0_to_1;
               }
               else
               {
                  static const int s_scan_delta_0[] = { 0 };
                  params.m_scan_delta_size = RG_ETC1_ARRAY_SIZE(s_scan_delta_0);
                  params.m_pScan_deltas = s_scan_delta_0;
               }
               
               optimizer.init(params, results[subblock]);
               if (!optimizer.compute())
                  break;
                              
               if (params.m_quality >= cMediumQuality)
               {
                  // TODO: Fix fairly arbitrary/unrefined thresholds that control how far away to scan for potentially better solutions.
                  const uint refinement_error_thresh0 = 3000;
                  const uint refinement_error_thresh1 = 6000;
                  if (results[subblock].m_error > refinement_error_thresh0)
                  {
                     if (params.m_quality == cMediumQuality)
                     {
                        static const int s_scan_delta_2_to_3[] = { -3, -2, 2, 3 };
                        params.m_scan_delta_size = RG_ETC1_ARRAY_SIZE(s_scan_delta_2_to_3);
                        params.m_pScan_deltas = s_scan_delta_2_to_3;
                     }
                     else
                     {
                        static const int s_scan_delta_5_to_5[] = { -5, 5 };
                        static const int s_scan_delta_5_to_8[] = { -8, -7, -6, -5, 5, 6, 7, 8 };
                        if (results[subblock].m_error > refinement_error_thresh1)
                        {
                           params.m_scan_delta_size = RG_ETC1_ARRAY_SIZE(s_scan_delta_5_to_8);
                           params.m_pScan_deltas = s_scan_delta_5_to_8;
                        }
                        else
                        {
                           params.m_scan_delta_size = RG_ETC1_ARRAY_SIZE(s_scan_delta_5_to_5);
                           params.m_pScan_deltas = s_scan_delta_5_to_5;
                        }
                     }

                     if (!optimizer.compute())
                        break;
                  }

                  if (results[2].m_error < results[subblock].m_error)
                     results[subblock] = results[2];
               }
                            
               trial_error += results[subblock].m_error;
               if (trial_error >= best_error)
                  break;
            }

            if (subblock < 2)
               continue;

            best_error = trial_error;
            best_results[0] = results[0];
            best_results[1] = results[1];
            best_flip = flip;
            best_use_color4 = use_color4;
            
         } // use_color4

      } // flip

      int dr = best_results[1].m_block_color_unscaled.r - best_results[0].m_block_color_unscaled.r;
      int dg = best_results[1].m_block_color_unscaled.g - best_results[0].m_block_color_unscaled.g;
      int db = best_results[1].m_block_color_unscaled.b - best_results[0].m_block_color_unscaled.b;
      RG_ETC1_ASSERT(best_use_color4 || (rg_etc1::minimum(dr, dg, db) >= cETC1ColorDeltaMin) && (rg_etc1::maximum(dr, dg, db) <= cETC1ColorDeltaMax));
           
      if (best_use_color4)
      {
         dst_block.m_bytes[0] = static_cast<uint8>(best_results[1].m_block_color_unscaled.r | (best_results[0].m_block_color_unscaled.r << 4));
         dst_block.m_bytes[1] = static_cast<uint8>(best_results[1].m_block_color_unscaled.g | (best_results[0].m_block_color_unscaled.g << 4));
         dst_block.m_bytes[2] = static_cast<uint8>(best_results[1].m_block_color_unscaled.b | (best_results[0].m_block_color_unscaled.b << 4));
      }
      else
      {
         if (dr < 0) dr += 8; dst_block.m_bytes[0] = static_cast<uint8>((best_results[0].m_block_color_unscaled.r << 3) | dr);
         if (dg < 0) dg += 8; dst_block.m_bytes[1] = static_cast<uint8>((best_results[0].m_block_color_unscaled.g << 3) | dg);
         if (db < 0) db += 8; dst_block.m_bytes[2] = static_cast<uint8>((best_results[0].m_block_color_unscaled.b << 3) | db);
      }
      
      dst_block.m_bytes[3] = static_cast<uint8>( (best_results[1].m_block_inten_table << 2) | (best_results[0].m_block_inten_table << 5) | ((~best_use_color4 & 1) << 1) | best_flip );
      
      uint selector0 = 0, selector1 = 0;
      if (best_flip)
      {
         // flipped:
         // { 0, 0 }, { 1, 0 }, { 2, 0 }, { 3, 0 },               
         // { 0, 1 }, { 1, 1 }, { 2, 1 }, { 3, 1 } 
         //
         // { 0, 2 }, { 1, 2 }, { 2, 2 }, { 3, 2 },
         // { 0, 3 }, { 1, 3 }, { 2, 3 }, { 3, 3 }
         const uint8* pSelectors0 = best_results[0].m_pSelectors;
         const uint8* pSelectors1 = best_results[1].m_pSelectors;
         for (int x = 3; x >= 0; --x)
         {
            uint b;
            b = g_selector_index_to_etc1[pSelectors1[4 + x]];
            selector0 = (selector0 << 1) | (b & 1); selector1 = (selector1 << 1) | (b >> 1);

            b = g_selector_index_to_etc1[pSelectors1[x]];
            selector0 = (selector0 << 1) | (b & 1); selector1 = (selector1 << 1) | (b >> 1);

            b = g_selector_index_to_etc1[pSelectors0[4 + x]];
            selector0 = (selector0 << 1) | (b & 1); selector1 = (selector1 << 1) | (b >> 1);

            b = g_selector_index_to_etc1[pSelectors0[x]];
            selector0 = (selector0 << 1) | (b & 1); selector1 = (selector1 << 1) | (b >> 1);
         }
      }
      else
      {
         // non-flipped:
         // { 0, 0 }, { 0, 1 }, { 0, 2 }, { 0, 3 },
         // { 1, 0 }, { 1, 1 }, { 1, 2 }, { 1, 3 }
         //
         // { 2, 0 }, { 2, 1 }, { 2, 2 }, { 2, 3 },
         // { 3, 0 }, { 3, 1 }, { 3, 2 }, { 3, 3 }
         for (int subblock = 1; subblock >= 0; --subblock)
         {
            const uint8* pSelectors = best_results[subblock].m_pSelectors + 4;
            for (uint i = 0; i < 2; i++)
            {
               uint b;
               b = g_selector_index_to_etc1[pSelectors[3]];
               selector0 = (selector0 << 1) | (b & 1); selector1 = (selector1 << 1) | (b >> 1);

               b = g_selector_index_to_etc1[pSelectors[2]];
               selector0 = (selector0 << 1) | (b & 1); selector1 = (selector1 << 1) | (b >> 1);

               b = g_selector_index_to_etc1[pSelectors[1]];
               selector0 = (selector0 << 1) | (b & 1); selector1 = (selector1 << 1) | (b >> 1);

               b = g_selector_index_to_etc1[pSelectors[0]];
               selector0 = (selector0 << 1) | (b & 1);selector1 = (selector1 << 1) | (b >> 1);

               pSelectors -= 4;
            }
         }
      }
                  
      dst_block.m_bytes[4] = static_cast<uint8>(selector1 >> 8); dst_block.m_bytes[5] = static_cast<uint8>(selector1 & 0xFF);
      dst_block.m_bytes[6] = static_cast<uint8>(selector0 >> 8); dst_block.m_bytes[7] = static_cast<uint8>(selector0 & 0xFF);

      return static_cast<unsigned int>(best_error);
   }

} // namespace rg_etc1