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anim_diff: add a -raw_comparison flag

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If this flag is not used, RGB is premultiplied before comparison.
Otherwise, the raw R/G/B values are compared, which can be a problem
in transparent area (alpha=0 R/G/B=anything)

Change-Id: I131cc10ec92414ad508b81f599a60d0097cac470
This commit is contained in:
Pascal Massimino
2015-07-07 22:45:49 +00:00
committed by James Zern
parent 155c1b222b
commit acb297e9c2
3 changed files with 40 additions and 12 deletions
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35
examples/anim_util.cc
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@ -815,20 +815,41 @@ bool ReadAnimatedImage(const char filename[], AnimatedImage* const image,
}
}
static void Accumulate(double v1, double v2, double* const max_diff,
double* const sse) {
const double diff = fabs(v1 - v2);
if (diff > *max_diff) *max_diff = diff;
*sse += diff * diff;
}
void GetDiffAndPSNR(const uint8_t rgba1[], const uint8_t rgba2[],
uint32_t width, uint32_t height, int* const max_diff,
double* const psnr) {
uint32_t width, uint32_t height, bool premultiply,
int* const max_diff, double* const psnr) {
const uint32_t stride = width * kNumChannels;
*max_diff = 0;
const int kAlphaChannel = kNumChannels - 1;
double f_max_diff = 0.;
double sse = 0.;
for (uint32_t y = 0; y < height; ++y) {
for (uint32_t x = 0; x < stride; ++x) {
for (uint32_t x = 0; x < stride; x += kNumChannels) {
const size_t offset = y * stride + x;
const int diff = abs(rgba1[offset] - rgba2[offset]);
if (diff > *max_diff) *max_diff = diff;
sse += diff * diff;
const int alpha1 = rgba1[offset + kAlphaChannel];
const int alpha2 = rgba2[offset + kAlphaChannel];
Accumulate(alpha1, alpha2, &f_max_diff, &sse);
if (!premultiply) {
for (int k = 0; k < kAlphaChannel; ++k) {
Accumulate(rgba1[offset + k], rgba2[offset + k], &f_max_diff, &sse);
}
} else {
// premultiply R/G/B channels with alpha value
for (int k = 0; k < kAlphaChannel; ++k) {
Accumulate(rgba1[offset + k] * alpha1 / 255.,
rgba2[offset + k] * alpha2 / 255.,
&f_max_diff, &sse);
}
}
}
}
*max_diff = static_cast<int>(f_max_diff);
if (*max_diff == 0) {
*psnr = 99.; // PSNR when images are identical.
} else {