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because of we divide by /255 not /256, we lose numerical precision, so can't guarantee that box filter results round to same results as naive

pull/43/head
Sean Barrett 2014-09-13 08:06:39 -07:00
parent adbbe8dabd
commit 1dcca19ae0
1 changed files with 6 additions and 4 deletions
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10
tests/resample_test.cpp
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@ -155,7 +155,7 @@ static void performance(int argc, char **argv)
out_w = w*2; out_h = h/4; count=20; // 2 // note this is structured pessimily, would be much faster to downsample vertically first out_w = w*2; out_h = h/4; count=20; // 2 // note this is structured pessimily, would be much faster to downsample vertically first
#elif 0 #elif 0
out_w = w/4; out_h = h*2; count=50; // 3 out_w = w/4; out_h = h*2; count=50; // 3
#elif 0 #elif 1
out_w = w*3; out_h = h*3; count=5; srgb=0; // 4 out_w = w*3; out_h = h*3; count=5; srgb=0; // 4
#else #else
out_w = w*3; out_h = h*3; count=3; // 5 // this is dominated by linear->sRGB conversion out_w = w*3; out_h = h*3; count=3; // 5 // this is dominated by linear->sRGB conversion
@ -181,7 +181,7 @@ int main(int argc, char** argv)
int out_w, out_h, out_stride; int out_w, out_h, out_stride;
//resizer(argc, argv); //resizer(argc, argv);
performance(argc, argv); //performance(argc, argv);
#if 1 #if 1
test_suite(argc, argv); test_suite(argc, argv);
@ -648,10 +648,10 @@ void verify_box(void)
+ image88[j*2+0][i*2+1] + image88[j*2+0][i*2+1]
+ image88[j*2+1][i*2+0] + image88[j*2+1][i*2+0]
+ image88[j*2+1][i*2+1]; + image88[j*2+1][i*2+1];
STBIR_ASSERT(output44[j][i] == ((n+2)>>2)); STBIR_ASSERT(output44[j][i] == ((n+2)>>2) || output44[j][i] == ((n+1)>>2)); // can't guarantee exact rounding due to numerical precision
t += n; t += n;
} }
STBIR_ASSERT(output11[0][0] == ((t+32)>>6)); STBIR_ASSERT(output11[0][0] == ((t+32)>>6) || output11[0][0] == ((t+31)>>6)); // can't guarantee exact rounding due to numerical precision
} }
void verify_filter_normalized(stbir_filter filter, int output_size, unsigned int value) void verify_filter_normalized(stbir_filter filter, int output_size, unsigned int value)
@ -675,6 +675,8 @@ void test_filters(void)
{ {
int i,j; int i,j;
mtsrand(0);
for (i=0; i < sizeof(image88); ++i) for (i=0; i < sizeof(image88); ++i)
image88[0][i] = mtrand() & 255; image88[0][i] = mtrand() & 255;
verify_box(); verify_box();