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If alpha is zero then sneakily replace it with a very small nonzero so that the color data is preserved.

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Pre-process n1 so that we don't have to do it later on. Can't do n0 since it's used to find the coefficient index.
This commit is contained in:
Jorge Rodriguez
2014-09-09 17:03:20 -07:00
parent d510d70b6a
commit 4b69c0637e
2 changed files with 65 additions and 18 deletions
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57
tests/resample_test.cpp
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@ -384,18 +384,21 @@ void test_subpixel(const char* file, float width_percent, float height_percent,
free(output_data);
}
unsigned char* pixel(unsigned char* buffer, int x, int y, int c, int w, int n)
unsigned int* pixel(unsigned int* buffer, int x, int y, int c, int w, int n)
{
return &buffer[y*w*n + x*n + c];
}
void test_premul()
{
unsigned char input[2 * 2 * 4];
unsigned char output[1 * 1 * 4];
unsigned int input[2 * 2 * 4];
unsigned int output[1 * 1 * 4];
unsigned int output2[2 * 2 * 4];
memset(input, 0, sizeof(input));
// First a test to make sure premul is working properly.
// Top left - solid red
*pixel(input, 0, 0, 0, 2, 4) = 255;
*pixel(input, 0, 0, 3, 2, 4) = 255;
@ -412,18 +415,50 @@ void test_premul()
*pixel(input, 1, 1, 1, 2, 4) = 255;
*pixel(input, 1, 1, 3, 2, 4) = 25;
stbir_resize_uint8_generic(input, 2, 2, 0, output, 1, 1, 0, 4, 3, 0, STBIR_EDGE_CLAMP, STBIR_FILTER_BOX, STBIR_COLORSPACE_LINEAR, &g_context);
stbir_resize(input, 2, 2, 0, output, 1, 1, 0, STBIR_TYPE_UINT32, 4, 3, 0, STBIR_EDGE_CLAMP, STBIR_EDGE_CLAMP, STBIR_FILTER_BOX, STBIR_FILTER_BOX, STBIR_COLORSPACE_LINEAR, &g_context);
float r = 1.0f;
float g = 1.0f;
float ra = 1.0;
float ga = (float)25 / 255;
float r = (float)255 / 4294967296;
float g = (float)255 / 4294967296;
float ra = (float)255 / 4294967296;
float ga = (float)25 / 4294967296;
float a = (ra + ga) / 2;
STBIR_ASSERT(output[0] == (int)(r * ra / 2 / a * 255 + 0.5f)); // 232
STBIR_ASSERT(output[1] == (int)(g * ga / 2 / a * 255 + 0.5f)); // 23
STBIR_ASSERT(output[0] == (int)(r * ra / 2 / a * 4294967296 + 0.5f)); // 232
STBIR_ASSERT(output[1] == (int)(g * ga / 2 / a * 4294967296 + 0.5f)); // 23
STBIR_ASSERT(output[2] == 0);
STBIR_ASSERT(output[3] == (int)(a * 255 + 0.5f)); // 140
STBIR_ASSERT(output[3] == (int)(a * 4294967296 + 0.5f)); // 140
// Now a test to make sure it doesn't clobber existing values.
// Top right - completely transparent green
*pixel(input, 1, 0, 1, 2, 4) = 255;
*pixel(input, 1, 0, 3, 2, 4) = 0;
// Bottom right - completely transparent green
*pixel(input, 1, 1, 1, 2, 4) = 255;
*pixel(input, 1, 1, 3, 2, 4) = 0;
stbir_resize(input, 2, 2, 0, output2, 2, 2, 0, STBIR_TYPE_UINT32, 4, 3, 0, STBIR_EDGE_CLAMP, STBIR_EDGE_CLAMP, STBIR_FILTER_BOX, STBIR_FILTER_BOX, STBIR_COLORSPACE_LINEAR, &g_context);
STBIR_ASSERT(*pixel(output2, 0, 0, 0, 2, 4) == 255);
STBIR_ASSERT(*pixel(output2, 0, 0, 1, 2, 4) == 0);
STBIR_ASSERT(*pixel(output2, 0, 0, 2, 2, 4) == 0);
STBIR_ASSERT(*pixel(output2, 0, 0, 3, 2, 4) == 255);
STBIR_ASSERT(*pixel(output2, 0, 1, 0, 2, 4) == 255);
STBIR_ASSERT(*pixel(output2, 0, 1, 1, 2, 4) == 0);
STBIR_ASSERT(*pixel(output2, 0, 1, 2, 2, 4) == 0);
STBIR_ASSERT(*pixel(output2, 0, 1, 3, 2, 4) == 255);
STBIR_ASSERT(*pixel(output2, 1, 0, 0, 2, 4) == 0);
STBIR_ASSERT(*pixel(output2, 1, 0, 1, 2, 4) == 255);
STBIR_ASSERT(*pixel(output2, 1, 0, 2, 2, 4) == 0);
STBIR_ASSERT(*pixel(output2, 1, 0, 3, 2, 4) == 0);
STBIR_ASSERT(*pixel(output2, 1, 1, 0, 2, 4) == 0);
STBIR_ASSERT(*pixel(output2, 1, 1, 1, 2, 4) == 255);
STBIR_ASSERT(*pixel(output2, 1, 1, 2, 2, 4) == 0);
STBIR_ASSERT(*pixel(output2, 1, 1, 3, 2, 4) == 0);
}
// test that splitting a pow-2 image into tiles produces identical results