forked from enlightenment/efl
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).
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@ -54,6 +54,17 @@ expand_bitmap(DATA8 *src, int pitch, int w, int h, DATA8 *dst)
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}
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}
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static inline DATA8
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alpha8to4(int a8)
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{
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// a4 values are 0x00, 0x11, 0x22, 0x33, ... 0xee, 0xff
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// increments by 0x11 = 17
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int a4 = (a8 >> 4) & 0x0f;
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int v = (a4 << 4) | a4;
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if ((a8 - v) > 8) a4++;
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else if ((v - a8) > 8) a4--;
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return a4; // v = (a4 << 4) | a4;
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}
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@ -149,11 +160,8 @@ compress_rle4(DATA8 *src, int pitch, int w, int h, int *size_ret)
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spanval = spanlen = spannum = 0;
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for (x = 0; x < w; x++)
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{
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// we only need upper 4 bits of value for span creation
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DATA8 v = pix[x] >> 4;
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// round-up if closer to upper value
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if ((pix[x] & 0x8) && (v != 0xF))
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v++;
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// round value from a8 to a44
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DATA8 v = alpha8to4(pix[x]);
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// if the current pixel value (in 4bit) is not the same as the
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// span value (n 4 bit) OR... if the span now exceeds 16 pixels
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// then add/write out the span to our RLE span blob
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@ -347,10 +355,8 @@ compress_bpp4(DATA8 *src, int pitch, int w, int h, int *size_ret)
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// 4 bits only needed) and pack
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for (x = 0; x < (w - 1); x += 2)
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{
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DATA8 v1 = s[0] >> 4;
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DATA8 v2 = s[1] >> 4;
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if ((s[0] & 0x08) && (v1 != 0x0f)) v1++;
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if ((s[1] & 0x08) && (v2 != 0x0f)) v2++;
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DATA8 v1 = alpha8to4(s[0]);
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DATA8 v2 = alpha8to4(s[1]);
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*d = (v1 << 4) | v2;
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s += 2;
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d++;
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