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allow alpha channel to be channel #0

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This commit is contained in:
Sean Barrett 2014-08-11 02:34:50 -07:00
parent f502cae91a
commit 6ade66182c
1 changed files with 6 additions and 5 deletions
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11
stb_resample.h
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@ -842,14 +842,15 @@ static void stbr__decode_scanline(stbr__info* stbr_info, int n)
break; break;
} }
if (alpha_channel) if (alpha_channel >= 0)
{ {
float alpha = decode_buffer[decode_pixel_index + alpha_channel];
for (c = 0; c < channels; c++) for (c = 0; c < channels; c++)
{ {
if (c == alpha_channel) if (c == alpha_channel)
continue; continue;
decode_buffer[decode_pixel_index + c] *= decode_buffer[decode_pixel_index + alpha_channel]; decode_buffer[decode_pixel_index + c] *= alpha;
} }
} }
} }
@ -1007,7 +1008,7 @@ static stbr_inline void stbr__encode_pixel(void* output_buffer, int output_pixel
int n; int n;
float divide_alpha = 1; float divide_alpha = 1;
if (alpha_channel) { if (alpha_channel >= 0) {
float alpha = encode_buffer[encode_pixel_index + alpha_channel]; float alpha = encode_buffer[encode_pixel_index + alpha_channel];
float reciprocal_alpha = alpha ? 1.0f / alpha : 0; float reciprocal_alpha = alpha ? 1.0f / alpha : 0;
for (n = 0; n < channels; n++) for (n = 0; n < channels; n++)
@ -1377,9 +1378,9 @@ static int stbr__resize_advanced(const void* input_data, int input_w, int input_
if (s1 > 1 || s0 < 0 || t1 > 1 || t0 < 0) if (s1 > 1 || s0 < 0 || t1 > 1 || t0 < 0)
return 0; return 0;
STBR_ASSERT(alpha_channel >= 0 && alpha_channel < channels); STBR_ASSERT(alpha_channel < channels);
if (alpha_channel < 0 || alpha_channel >= channels) if (alpha_channel >= channels)
return 0; return 0;
STBR_ASSERT(tempmem); STBR_ASSERT(tempmem);