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// Copyright 2017 Google Inc. All Rights Reserved.
//
// Use of this source code is governed by a BSD-style license
// that can be found in the COPYING file in the root of the source
// tree. An additional intellectual property rights grant can be found
// in the file PATENTS. All contributing project authors may
// be found in the AUTHORS file in the root of the source tree.
// -----------------------------------------------------------------------------
//
// distortion calculation
//
// Author: Skal (pascal.massimino@gmail.com)
#include <assert.h>
#include <stdlib.h> // for abs()
#include "src/dsp/dsp.h"
#if !defined(WEBP_REDUCE_SIZE)
//------------------------------------------------------------------------------
// SSIM / PSNR
// hat-shaped filter. Sum of coefficients is equal to 16.
static const uint32_t kWeight[2 * VP8_SSIM_KERNEL + 1] = {
1, 2, 3, 4, 3, 2, 1
};
static const uint32_t kWeightSum = 16 * 16; // sum{kWeight}^2
static WEBP_INLINE double SSIMCalculation(
const VP8DistoStats* const stats, uint32_t N /*num samples*/) {
const uint32_t w2 = N * N;
const uint32_t C1 = 20 * w2;
const uint32_t C2 = 60 * w2;
const uint32_t C3 = 8 * 8 * w2; // 'dark' limit ~= 6
const uint64_t xmxm = (uint64_t)stats->xm * stats->xm;
const uint64_t ymym = (uint64_t)stats->ym * stats->ym;
if (xmxm + ymym >= C3) {
const int64_t xmym = (int64_t)stats->xm * stats->ym;
const int64_t sxy = (int64_t)stats->xym * N - xmym; // can be negative
const uint64_t sxx = (uint64_t)stats->xxm * N - xmxm;
const uint64_t syy = (uint64_t)stats->yym * N - ymym;
// we descale by 8 to prevent overflow during the fnum/fden multiply.
const uint64_t num_S = (2 * (uint64_t)(sxy < 0 ? 0 : sxy) + C2) >> 8;
const uint64_t den_S = (sxx + syy + C2) >> 8;
const uint64_t fnum = (2 * xmym + C1) * num_S;
const uint64_t fden = (xmxm + ymym + C1) * den_S;
const double r = (double)fnum / fden;
assert(r >= 0. && r <= 1.0);
return r;
}
return 1.; // area is too dark to contribute meaningfully
}
double VP8SSIMFromStats(const VP8DistoStats* const stats) {
return SSIMCalculation(stats, kWeightSum);
}
double VP8SSIMFromStatsClipped(const VP8DistoStats* const stats) {
return SSIMCalculation(stats, stats->w);
}
static double SSIMGetClipped_C(const uint8_t* src1, int stride1,
const uint8_t* src2, int stride2,
int xo, int yo, int W, int H) {
VP8DistoStats stats = { 0, 0, 0, 0, 0, 0 };
const int ymin = (yo - VP8_SSIM_KERNEL < 0) ? 0 : yo - VP8_SSIM_KERNEL;
const int ymax = (yo + VP8_SSIM_KERNEL > H - 1) ? H - 1
: yo + VP8_SSIM_KERNEL;
const int xmin = (xo - VP8_SSIM_KERNEL < 0) ? 0 : xo - VP8_SSIM_KERNEL;
const int xmax = (xo + VP8_SSIM_KERNEL > W - 1) ? W - 1
: xo + VP8_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[VP8_SSIM_KERNEL + x - xo]
* kWeight[VP8_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 VP8SSIMFromStatsClipped(&stats);
}
static double SSIMGet_C(const uint8_t* src1, int stride1,
const uint8_t* src2, int stride2) {
VP8DistoStats stats = { 0, 0, 0, 0, 0, 0 };
int x, y;
for (y = 0; y <= 2 * VP8_SSIM_KERNEL; ++y, src1 += stride1, src2 += stride2) {
for (x = 0; x <= 2 * VP8_SSIM_KERNEL; ++x) {
const uint32_t w = kWeight[x] * kWeight[y];
const uint32_t s1 = src1[x];
const uint32_t s2 = src2[x];
stats.xm += w * s1;
stats.ym += w * s2;
stats.xxm += w * s1 * s1;
stats.xym += w * s1 * s2;
stats.yym += w * s2 * s2;
}
}
return VP8SSIMFromStats(&stats);
}
#endif // !defined(WEBP_REDUCE_SIZE)
//------------------------------------------------------------------------------
#if !defined(WEBP_DISABLE_STATS)
static uint32_t AccumulateSSE_C(const uint8_t* src1,
const uint8_t* src2, int len) {
int i;
uint32_t sse2 = 0;
assert(len <= 65535); // to ensure that accumulation fits within uint32_t
for (i = 0; i < len; ++i) {
const int32_t diff = src1[i] - src2[i];
sse2 += diff * diff;
}
return sse2;
}
#endif
//------------------------------------------------------------------------------
#if !defined(WEBP_REDUCE_SIZE)
VP8SSIMGetFunc VP8SSIMGet;
VP8SSIMGetClippedFunc VP8SSIMGetClipped;
#endif
#if !defined(WEBP_DISABLE_STATS)
VP8AccumulateSSEFunc VP8AccumulateSSE;
#endif
extern void VP8SSIMDspInitSSE2(void);
WEBP_DSP_INIT_FUNC(VP8SSIMDspInit) {
#if !defined(WEBP_REDUCE_SIZE)
VP8SSIMGetClipped = SSIMGetClipped_C;
VP8SSIMGet = SSIMGet_C;
#endif
#if !defined(WEBP_DISABLE_STATS)
VP8AccumulateSSE = AccumulateSSE_C;
#endif
if (VP8GetCPUInfo != NULL) {
#if defined(WEBP_USE_SSE2)
if (VP8GetCPUInfo(kSSE2)) {
VP8SSIMDspInitSSE2();
}
#endif
}
}
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