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Try to keep integer precision by briefly casting to double while decoding and encoding.

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This commit is contained in:
Jorge Rodriguez 2014-07-30 01:18:23 -07:00
parent 11897fbf96
commit 6625259959
2 changed files with 8 additions and 8 deletions
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8
stb_resample.h
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@ -715,12 +715,12 @@ static void stbr__decode_scanline(stbr__info* stbr_info, int n)
case STBR__DECODE(STBR_TYPE_UINT32, STBR_COLORSPACE_LINEAR): case STBR__DECODE(STBR_TYPE_UINT32, STBR_COLORSPACE_LINEAR):
for (int n = 0; n < channels; n++) for (int n = 0; n < channels; n++)
decode_buffer[decode_texel_index + n] = ((float)((const unsigned int*)input_data)[input_texel_index + n]) / 4294967295; decode_buffer[decode_texel_index + n] = (float)(((double)((const unsigned int*)input_data)[input_texel_index + n]) / 4294967295);
break; break;
case STBR__DECODE(STBR_TYPE_UINT32, STBR_COLORSPACE_SRGB): case STBR__DECODE(STBR_TYPE_UINT32, STBR_COLORSPACE_SRGB):
for (int n = 0; n < channels; n++) for (int n = 0; n < channels; n++)
decode_buffer[decode_texel_index + n] = stbr__srgb_to_linear(((float)((const unsigned int*)input_data)[input_texel_index + n]) / 4294967295); decode_buffer[decode_texel_index + n] = stbr__srgb_to_linear((float)(((double)((const unsigned int*)input_data)[input_texel_index + n]) / 4294967295));
break; break;
case STBR__DECODE(STBR_TYPE_FLOAT, STBR_COLORSPACE_LINEAR): case STBR__DECODE(STBR_TYPE_FLOAT, STBR_COLORSPACE_LINEAR):
@ -913,12 +913,12 @@ static stbr_inline void stbr__encode_scanline(void* output_buffer, int output_te
case STBR__DECODE(STBR_TYPE_UINT32, STBR_COLORSPACE_LINEAR): case STBR__DECODE(STBR_TYPE_UINT32, STBR_COLORSPACE_LINEAR):
for (int n = 0; n < channels; n++) for (int n = 0; n < channels; n++)
((unsigned int*)output_buffer)[output_texel_index + n] = (unsigned int)(stbr__saturate(encode_buffer[encode_texel_index + n]) * 4294967295); ((unsigned int*)output_buffer)[output_texel_index + n] = (unsigned int)(((double)stbr__saturate(encode_buffer[encode_texel_index + n])) * 4294967295);
break; break;
case STBR__DECODE(STBR_TYPE_UINT32, STBR_COLORSPACE_SRGB): case STBR__DECODE(STBR_TYPE_UINT32, STBR_COLORSPACE_SRGB):
for (int n = 0; n < channels; n++) for (int n = 0; n < channels; n++)
((unsigned int*)output_buffer)[output_texel_index + n] = (unsigned int)(stbr__linear_to_srgb(stbr__saturate(encode_buffer[encode_texel_index + n])) * 4294967295); ((unsigned int*)output_buffer)[output_texel_index + n] = (unsigned int)(((double)stbr__linear_to_srgb(stbr__saturate(encode_buffer[encode_texel_index + n]))) * 4294967295);
break; break;
case STBR__DECODE(STBR_TYPE_FLOAT, STBR_COLORSPACE_LINEAR): case STBR__DECODE(STBR_TYPE_FLOAT, STBR_COLORSPACE_LINEAR):

8
tests/resample_test.cpp
View File

@ -128,9 +128,9 @@ void resize_image(const char* filename, float width_percent, float height_percen
template <typename F, typename T> template <typename F, typename T>
void convert_image(const F* input, T* output, int length) void convert_image(const F* input, T* output, int length)
{ {
float f = (pow(2.0f, 8.0f * sizeof(T)) - 1) / (pow(2.0f, 8.0f * sizeof(F)) - 1); double f = (pow(2.0, 8.0 * sizeof(T)) - 1) / (pow(2.0, 8.0 * sizeof(F)) - 1);
for (int i = 0; i < length; i++) for (int i = 0; i < length; i++)
output[i] = (T)(((float)input[i]) * f); output[i] = (T)(((double)input[i]) * f);
} }
template <typename T> template <typename T>
@ -155,8 +155,8 @@ void test_format(const char* file, float width_percent, float height_percent, st
free(T_data); free(T_data);
stbi_image_free(input_data); stbi_image_free(input_data);
char* char_data = (char*)malloc(new_w * new_h * n * sizeof(char)); unsigned char* char_data = (unsigned char*)malloc(new_w * new_h * n * sizeof(char));
convert_image<T, char>(output_data, char_data, new_w * new_h * n); convert_image<T, unsigned char>(output_data, char_data, new_w * new_h * n);
char output[200]; char output[200];
sprintf(output, "test-output/type-%d-%d-%d-%d-%s", type, colorspace, new_w, new_h, file); sprintf(output, "test-output/type-%d-%d-%d-%d-%s", type, colorspace, new_w, new_h, file);