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fix bug in png decoding with 1,2,4-bpp images using filter that samples previous line

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This commit is contained in:
Sean Barrett 2017-03-18 10:54:22 -07:00
parent ee19531f68
commit be6d13cd6d
1 changed files with 2 additions and 1 deletions
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stb_image.h
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@ -4201,7 +4201,7 @@ static int stbi__create_png_image_raw(stbi__png *a, stbi_uc *raw, stbi__uint32 r
for (j=0; j < y; ++j) { for (j=0; j < y; ++j) {
stbi_uc *cur = a->out + stride*j; stbi_uc *cur = a->out + stride*j;
stbi_uc *prior = cur - stride; stbi_uc *prior;
int filter = *raw++; int filter = *raw++;
if (filter > 4) if (filter > 4)
@ -4213,6 +4213,7 @@ static int stbi__create_png_image_raw(stbi__png *a, stbi_uc *raw, stbi__uint32 r
filter_bytes = 1; filter_bytes = 1;
width = img_width_bytes; width = img_width_bytes;
} }
prior = cur - stride; // bugfix: need to compute this after 'cur +=' computation above
// if first row, use special filter that doesn't sample previous row // if first row, use special filter that doesn't sample previous row
if (j == 0) filter = first_row_filter[filter]; if (j == 0) filter = first_row_filter[filter];