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Evas font: Improve RLE rounding alpha8 to alpha44 

This should ensure that the difference between the original
pixel value and the rle4 encoded one is <= 8.

The previous fix was a bit stupid as it was not taking into
account the conversion a4 to a8 (which is a8 = (a4 << 4) | a4).
This commit is contained in:
Jean-Philippe Andre 2014-12-09 11:00:38 +09:00
parent 9dbd2db21b
commit 624787c42a
1 changed files with 15 additions and 9 deletions
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24
src/lib/evas/common/evas_font_compress.c
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@ -54,6 +54,17 @@ expand_bitmap(DATA8 *src, int pitch, int w, int h, DATA8 *dst)
}
}
static inline DATA8
alpha8to4(int a8)
{
// a4 values are 0x00, 0x11, 0x22, 0x33, ... 0xee, 0xff
// increments by 0x11 = 17
int a4 = (a8 >> 4) & 0x0f;
int v = (a4 << 4) | a4;
if ((a8 - v) > 8) a4++;
else if ((v - a8) > 8) a4--;
return a4; // v = (a4 << 4) | a4;
}
@ -149,11 +160,8 @@ compress_rle4(DATA8 *src, int pitch, int w, int h, int *size_ret)
spanval = spanlen = spannum = 0;
for (x = 0; x < w; x++)
{
// we only need upper 4 bits of value for span creation
DATA8 v = pix[x] >> 4;
// round-up if closer to upper value
if ((pix[x] & 0x8) && (v != 0xF))
v++;
// round value from a8 to a44
DATA8 v = alpha8to4(pix[x]);
// if the current pixel value (in 4bit) is not the same as the
// span value (n 4 bit) OR... if the span now exceeds 16 pixels
// then add/write out the span to our RLE span blob
@ -347,10 +355,8 @@ compress_bpp4(DATA8 *src, int pitch, int w, int h, int *size_ret)
// 4 bits only needed) and pack
for (x = 0; x < (w - 1); x += 2)
{
DATA8 v1 = s[0] >> 4;
DATA8 v2 = s[1] >> 4;
if ((s[0] & 0x08) && (v1 != 0x0f)) v1++;
if ((s[1] & 0x08) && (v2 != 0x0f)) v2++;
DATA8 v1 = alpha8to4(s[0]);
DATA8 v2 = alpha8to4(s[1]);
*d = (v1 << 4) | v2;
s += 2;
d++;