static double SSIMGetClipped(const uint8_t* src1, int stride1,
const uint8_t* src2, int stride2,
int xo, int yo, int W, int H) {
DistoStats stats = { 0, 0, 0, 0, 0, 0 };
const int ymin = (yo - SSIM_KERNEL < 0) ? 0 : yo - SSIM_KERNEL;
const int ymax = (yo + SSIM_KERNEL > H - 1) ? H - 1 : yo + SSIM_KERNEL;
const int xmin = (xo - SSIM_KERNEL < 0) ? 0 : xo - SSIM_KERNEL;
const int xmax = (xo + SSIM_KERNEL > W - 1) ? W - 1 : xo + SSIM_KERNEL;
int x, y;
src1 += ymin * stride1;
src2 += ymin * stride2;
for (y = ymin; y <= ymax; ++y, src1 += stride1, src2 += stride2) {
for (x = xmin; x <= xmax; ++x) {
const uint32_t w = kWeight[SSIM_KERNEL + x - xo]
* kWeight[SSIM_KERNEL + y - yo];
const uint32_t s1 = src1[x];
const uint32_t s2 = src2[x];
stats.w += w;
stats.xm += w * s1;
stats.ym += w * s2;
stats.xxm += w * s1 * s1;
stats.xym += w * s1 * s2;
stats.yym += w * s2 * s2;
}
}
return SSIMCalculation(&stats);
}
double VP8SSIMFromStatsClipped(const VP8DistoStats* const stats) {
return SSIMCalculation(stats, stats->w);
}
double VP8SSIMFromStats(const VP8DistoStats* const stats) {
return SSIMCalculation(stats, kWeightSum);
}
