sean-m
/
stb
mirror of https://github.com/nothings/stb.git
1
0
Fork 0
Code Issues Releases Activity

Replace premul test with better premul test that doesn't require visual inspection.

pull/43/head
Jorge Rodriguez 2014-09-09 16:30:06 -07:00
parent 497eab8339
commit 084baed15c
1 changed files with 31 additions and 29 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

60
tests/resample_test.cpp
View File

@ -384,44 +384,46 @@ void test_subpixel(const char* file, float width_percent, float height_percent,
free(output_data);
}
void test_premul(const char* file)
unsigned char* pixel(unsigned char* buffer, int x, int y, int c, int w, int n)
{
int w, h, n;
unsigned char* input_data = stbi_load(file, &w, &h, &n, 4);
n = 4;
return &buffer[y*w*n + x*n + c];
}
if (input_data == NULL)
return;
void test_premul()
{
unsigned char input[2 * 2 * 4];
unsigned char output[1 * 1 * 4];
memset(input, 0, sizeof(input));
// Set alpha for the top half.
for (int x = 0; x < w; x++)
{
for (int y = 0; y < h / 2; y++)
input_data[(y*w + x)*n + 3] = input_data[(y*w + x)*n + 0];
}
// Top left - solid red
*pixel(input, 0, 0, 0, 2, 4) = 255;
*pixel(input, 0, 0, 3, 2, 4) = 255;
stbi_write_png("test-output/premul-original.png", w, h, n, input_data, 0);
// Bottom left - solid red
*pixel(input, 0, 1, 0, 2, 4) = 255;
*pixel(input, 0, 1, 3, 2, 4) = 255;
int new_w = (int)(w * .1);
int new_h = (int)(h * .1);
// Top right - transparent green
*pixel(input, 1, 0, 1, 2, 4) = 255;
*pixel(input, 1, 0, 3, 2, 4) = 25;
unsigned char* output_data = (unsigned char*)malloc(new_w * new_h * n * sizeof(unsigned char));
// Bottom right - transparent green
*pixel(input, 1, 1, 1, 2, 4) = 255;
*pixel(input, 1, 1, 3, 2, 4) = 25;
stbir_resize_uint8_generic(input_data, w, h, 0, output_data, new_w, new_h, 0, n, n - 1, 0, STBIR_EDGE_CLAMP, STBIR_FILTER_CATMULLROM, STBIR_COLORSPACE_SRGB, &g_context);
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);
char output[200];
sprintf(output, "test-output/premul-%s", file);
stbi_write_png(output, new_w, new_h, n, output_data, 0);
float r = 1.0f;
float g = 1.0f;
float ra = 1.0;
float ga = (float)25 / 255;
float a = (ra + ga) / 2;
stbir_resize_uint8_generic(input_data, w, h, 0, output_data, new_w, new_h, 0, n, n - 1, STBIR_FLAG_PREMULTIPLIED_ALPHA, STBIR_EDGE_CLAMP, STBIR_FILTER_CATMULLROM, STBIR_COLORSPACE_SRGB, &g_context);
sprintf(output, "test-output/nopremul-%s", file);
stbi_write_png(output, new_w, new_h, n, output_data, 0);
stbi_image_free(input_data);
free(output_data);
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[2] == 0);
STBIR_ASSERT(output[3] == (int)(a * 255 + 0.5f)); // 140
}
// test that splitting a pow-2 image into tiles produces identical results
@ -713,7 +715,7 @@ void test_suite(int argc, char **argv)
test_subpixel_3();
test_subpixel_4();
test_premul(barbara);
test_premul();
for (i = 0; i < 10; i++)
test_subpixel(barbara, 0.5f, 0.5f, (float)i / 10, 1);