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stb_truetype: Cancel out phase offset from box filter correctly.

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This commit is contained in:
Fabian Giesen 2014-12-08 19:20:41 -08:00
parent 8ac41a413d
commit 5f674fc7e5
1 changed files with 14 additions and 2 deletions
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16
stb_truetype.h
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@ -2275,13 +2275,25 @@ static void stbtt__v_prefilter(unsigned char *pixels, int w, int h, int stride_i
} }
} }
static float stbtt__oversample_shift(int oversample)
{
if (!oversample)
return 0.0f;
// The prefilter is a box filter of width "oversample",
// which shifts phase by (oversample - 1)/2 pixels in
// oversampled space. We want to shift in the opposite
// direction to counter this.
return (float)-(oversample - 1) / (2.0f * (float)oversample);
}
int stbtt_PackFontRanges(stbtt_pack_context *spc, unsigned char *fontdata, int font_index, stbtt_pack_range *ranges, int num_ranges) int stbtt_PackFontRanges(stbtt_pack_context *spc, unsigned char *fontdata, int font_index, stbtt_pack_range *ranges, int num_ranges)
{ {
stbtt_fontinfo info; stbtt_fontinfo info;
float recip_h = 1.0f / spc->h_oversample; float recip_h = 1.0f / spc->h_oversample;
float recip_v = 1.0f / spc->v_oversample; float recip_v = 1.0f / spc->v_oversample;
float sub_x = spc->h_oversample ? recip_h : 0; float sub_x = stbtt__oversample_shift(spc->h_oversample);
float sub_y = spc->v_oversample ? recip_v : 0; float sub_y = stbtt__oversample_shift(spc->v_oversample);
int i,j,k,n, return_value = 1; int i,j,k,n, return_value = 1;
stbrp_context *context = (stbrp_context *) spc->pack_info; stbrp_context *context = (stbrp_context *) spc->pack_info;
stbrp_rect *rects; stbrp_rect *rects;