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Fix alpha multiplication for images with unassociated alpha

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Abdelrahman Said 2024-05-06 00:54:25 +01:00
parent d278d7ee55
commit efad22f21e
1 changed files with 11 additions and 3 deletions
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14
src/tiff/tiffread.c
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@ -221,6 +221,8 @@ internal bool read_field(const TiffField *field, TiffImage *img);
internal bool validate_image_type(const TiffImage *img); internal bool validate_image_type(const TiffImage *img);
internal void fread_with_offset(FILE *fp, void *dst, u64 count, u64 offset); internal void fread_with_offset(FILE *fp, void *dst, u64 count, u64 offset);
internal bool valid_tiff_file(const char *file); internal bool valid_tiff_file(const char *file);
internal f32 u8_normalise(u8 value);
internal u8 u8_denormalise(f32 value);
Image *read_baseline_tiff(const char *file, Arena *arena) { Image *read_baseline_tiff(const char *file, Arena *arena) {
Image *img_out = NULL; Image *img_out = NULL;
@ -608,9 +610,11 @@ internal void read_strips(TiffReader *reader) {
fread_with_offset(reader->fp, &(p->a), 1, alpha_offset); fread_with_offset(reader->fp, &(p->a), 1, alpha_offset);
if (alpha.type == ALPHA_TYPE_UNASSOCIATED) { if (alpha.type == ALPHA_TYPE_UNASSOCIATED) {
p->r *= p->a; f32 a_norm = u8_normalise(p->a);
p->g *= p->a;
p->b *= p->a; p->r = u8_denormalise(u8_normalise(p->r) * a_norm);
p->g = u8_denormalise(u8_normalise(p->g) * a_norm);
p->b = u8_denormalise(u8_normalise(p->b) * a_norm);
} }
} }
@ -857,3 +861,7 @@ internal bool valid_tiff_file(const char *file) {
return true; return true;
} }
internal f32 u8_normalise(u8 value) { return (f32)value / (f32)UINT8_MAX; }
internal u8 u8_denormalise(f32 value) { return (u8)(value * UINT8_MAX); }