diff --git a/README b/README
index 11676ff9..da72c90b 100644
--- a/README
+++ b/README
@@ -148,6 +148,8 @@ options:
-crop <x> <y> <w> <h> .. crop picture with the given rectangle
-resize <w> <h> ........ resize picture (after any cropping)
-map <int> ............. print map of extra info.
+ -print_ssim ............ prints averaged SSIM distortion.
+ -print_psnr ............ prints averaged PSNR distortion.
-d <file.pgm> .......... dump the compressed output (PGM file).
-alpha_method <int> .... Transparency-compression method (0..1)
-alpha_filter <string> . predictive filtering for alpha plane.
diff --git a/examples/cwebp.c b/examples/cwebp.c
index d9067dc0..9d31bb17 100644
--- a/examples/cwebp.c
+++ b/examples/cwebp.c
@@ -529,7 +529,8 @@ static void PrintValues(const int values[4]) {
fprintf(stderr, "|\n");
}
-static void PrintExtraInfo(const WebPPicture* const pic, int short_output) {
+static void PrintExtraInfo(const WebPPicture* const pic, int short_output,
+ const char* const file_name) {
const WebPAuxStats* const stats = pic->stats;
if (short_output) {
fprintf(stderr, "%7d %2.2f\n", stats->coded_size, stats->PSNR[3]);
@@ -538,8 +539,11 @@ static void PrintExtraInfo(const WebPPicture* const pic, int short_output) {
const int num_i16 = stats->block_count[1];
const int num_skip = stats->block_count[2];
const int total = num_i4 + num_i16;
- fprintf(stderr,
- "%7d bytes Y-U-V-All-PSNR %2.2f %2.2f %2.2f %2.2f dB\n",
+ fprintf(stderr, "File: %s\n", file_name);
+ fprintf(stderr, "Dimension: %d x %d%s\n",
+ pic->width, pic->height, (pic->a != NULL) ? " (with alpha)" : "");
+ fprintf(stderr, "Output: "
+ "%d bytes Y-U-V-All-PSNR %2.2f %2.2f %2.2f %2.2f dB\n",
stats->coded_size,
stats->PSNR[0], stats->PSNR[1], stats->PSNR[2], stats->PSNR[3]);
if (total > 0) {
@@ -626,7 +630,7 @@ static int DumpPicture(const WebPPicture* const picture, const char* PGM_name) {
const int alpha_height = picture->a ? picture->height : 0;
const int height = picture->height + uv_height + alpha_height;
FILE* const f = fopen(PGM_name, "wb");
- if (!f) return 0;
+ if (f == NULL) return 0;
fprintf(f, "P5\n%d %d\n255\n", stride, height);
for (y = 0; y < picture->height; ++y) {
if (fwrite(picture->y + y * picture->y_stride, picture->width, 1, f) != 1)
@@ -707,6 +711,8 @@ static void HelpLong(void) {
printf(" -444 / -422 / -gray ..... Change colorspace\n");
#endif
printf(" -map <int> ............. print map of extra info.\n");
+ printf(" -print_ssim ............ prints averaged SSIM distortion.\n");
+ printf(" -print_psnr ............ prints averaged PSNR distortion.\n");
printf(" -d <file.pgm> .......... dump the compressed output (PGM file).\n");
printf(" -alpha_method <int> .... Transparency-compression method (0..1)\n");
printf(" -alpha_filter <string> . predictive filtering for alpha plane.\n");
@@ -766,11 +772,15 @@ int main(int argc, const char *argv[]) {
int resize_w = 0, resize_h = 0;
int show_progress = 0;
WebPPicture picture;
+ int print_distortion = 0; // 1=PSNR, 2=SSIM
+ WebPPicture original_picture; // when PSNR or SSIM is requested
WebPConfig config;
WebPAuxStats stats;
Stopwatch stop_watch;
- if (!WebPPictureInit(&picture) || !WebPConfigInit(&config)) {
+ if (!WebPPictureInit(&picture) ||
+ !WebPPictureInit(&original_picture) ||
+ !WebPConfigInit(&config)) {
fprintf(stderr, "Error! Version mismatch!\n");
goto Error;
}
@@ -792,6 +802,12 @@ int main(int argc, const char *argv[]) {
} else if (!strcmp(argv[c], "-d") && c < argc - 1) {
dump_file = argv[++c];
config.show_compressed = 1;
+ } else if (!strcmp(argv[c], "-print_ssim")) {
+ config.show_compressed = 1;
+ print_distortion = 2;
+ } else if (!strcmp(argv[c], "-print_psnr")) {
+ config.show_compressed = 1;
+ print_distortion = 1;
} else if (!strcmp(argv[c], "-short")) {
short_output++;
} else if (!strcmp(argv[c], "-s") && c < argc - 2) {
@@ -919,7 +935,7 @@ int main(int argc, const char *argv[]) {
StopwatchReadAndReset(&stop_watch);
}
if (!ReadPicture(in_file, &picture, keep_alpha)) {
- fprintf(stderr, "Error! Cannot read input picture\n");
+ fprintf(stderr, "Error! Cannot read input picture file '%s'\n", in_file);
goto Error;
}
picture.progress_hook = (show_progress && !quiet) ? ProgressReport : NULL;
@@ -932,7 +948,7 @@ int main(int argc, const char *argv[]) {
// Open the output
if (out_file) {
out = fopen(out_file, "wb");
- if (!out) {
+ if (out == NULL) {
fprintf(stderr, "Error! Cannot open output file '%s'\n", out_file);
goto Error;
} else {
@@ -969,6 +985,9 @@ int main(int argc, const char *argv[]) {
if (picture.extra_info_type > 0) {
AllocExtraInfo(&picture);
}
+ if (print_distortion > 0) { // Save original picture for later comparison
+ WebPPictureCopy(&picture, &original_picture);
+ }
if (!WebPEncode(&config, &picture)) {
fprintf(stderr, "Error! Cannot encode picture as WebP\n");
fprintf(stderr, "Error code: %d (%s)\n",
@@ -984,13 +1003,23 @@ int main(int argc, const char *argv[]) {
if (dump_file) {
DumpPicture(&picture, dump_file);
}
+
if (!quiet) {
- PrintExtraInfo(&picture, short_output);
+ PrintExtraInfo(&picture, short_output, in_file);
+ }
+ if (!quiet && !short_output && print_distortion > 0) { // print distortion
+ float values[5];
+ WebPPictureDistortion(&picture, &original_picture,
+ (print_distortion == 1) ? 0 : 1, values);
+ fprintf(stderr, "%s: Y:%.2f U:%.2f V:%.2f A:%.2f Total:%.2f\n",
+ (print_distortion == 1) ? "PSNR" : "SSIM",
+ values[0], values[1], values[2], values[3], values[4]);
}
Error:
free(picture.extra_info);
WebPPictureFree(&picture);
+ WebPPictureFree(&original_picture);
if (out != NULL) {
fclose(out);
}
diff --git a/man/cwebp.1 b/man/cwebp.1
index 2192fd5f..ec7ed8cf 100644
--- a/man/cwebp.1
+++ b/man/cwebp.1
@@ -168,6 +168,12 @@ Disable all assembly optimizations.
.B \-v
Print extra information (encoding time in particular).
.TP
+.B \-print_psnr
+Compute and report average PSNR (Peak-Signal-To-Noise ratio).
+.TP
+.B \-print_ssim
+Compute and report average SSIM (structural similarity metric)
+.TP
.B \-progress
Report encoding progress in percent.
.TP
diff --git a/src/enc/filter.c b/src/enc/filter.c
index ba659242..7fb78a39 100644
--- a/src/enc/filter.c
+++ b/src/enc/filter.c
@@ -234,14 +234,21 @@ static void DoFilter(const VP8EncIterator* const it, int level) {
// SSIM metric
enum { KERNEL = 3 };
-typedef struct {
- double w, xm, ym, xxm, xym, yym;
-} SSIMStats;
+static const double kMinValue = 1.e-10; // minimal threshold
-static void Accumulate(const uint8_t* src1, int stride1,
- const uint8_t* src2, int stride2,
- int xo, int yo, int W, int H,
- SSIMStats* const stats) {
+void VP8SSIMAddStats(const DistoStats* const src, DistoStats* const dst) {
+ dst->w += src->w;
+ dst->xm += src->xm;
+ dst->ym += src->ym;
+ dst->xxm += src->xxm;
+ dst->xym += src->xym;
+ dst->yym += src->yym;
+}
+
+static void VP8SSIMAccumulate(const uint8_t* src1, int stride1,
+ const uint8_t* src2, int stride2,
+ int xo, int yo, int W, int H,
+ DistoStats* const stats) {
const int ymin = (yo - KERNEL < 0) ? 0 : yo - KERNEL;
const int ymax = (yo + KERNEL > H - 1) ? H - 1 : yo + KERNEL;
const int xmin = (xo - KERNEL < 0) ? 0 : xo - KERNEL;
@@ -263,7 +270,7 @@ static void Accumulate(const uint8_t* src1, int stride1,
}
}
-static double GetSSIM(const SSIMStats* const stats) {
+double VP8SSIMGet(const DistoStats* const stats) {
const double xmxm = stats->xm * stats->xm;
const double ymym = stats->ym * stats->ym;
const double xmym = stats->xm * stats->ym;
@@ -281,26 +288,49 @@ static double GetSSIM(const SSIMStats* const stats) {
C2 = 58.5225 * w2;
fnum = (2 * xmym + C1) * (2 * sxy + C2);
fden = (xmxm + ymym + C1) * (sxx + syy + C2);
- return (fden != 0) ? fnum / fden : 0.;
+ return (fden != 0.) ? fnum / fden : kMinValue;
+}
+
+double VP8SSIMGetSquaredError(const DistoStats* const s) {
+ if (s->w > 0.) {
+ const double iw2 = 1. / (s->w * s->w);
+ const double sxx = s->xxm * s->w - s->xm * s->xm;
+ const double syy = s->yym * s->w - s->ym * s->ym;
+ const double sxy = s->xym * s->w - s->xm * s->ym;
+ const double SSE = iw2 * (sxx + syy - 2. * sxy);
+ if (SSE > kMinValue) return SSE;
+ }
+ return kMinValue;
+}
+
+void VP8SSIMAccumulatePlane(const uint8_t* src1, int stride1,
+ const uint8_t* src2, int stride2,
+ int W, int H, DistoStats* const stats) {
+ int x, y;
+ for (y = 0; y < H; ++y) {
+ for (x = 0; x < W; ++x) {
+ VP8SSIMAccumulate(src1, stride1, src2, stride2, x, y, W, H, stats);
+ }
+ }
}
static double GetMBSSIM(const uint8_t* yuv1, const uint8_t* yuv2) {
int x, y;
- SSIMStats s = { .0, .0, .0, .0, .0, .0 };
+ DistoStats s = { .0, .0, .0, .0, .0, .0 };
// compute SSIM in a 10 x 10 window
for (x = 3; x < 13; x++) {
for (y = 3; y < 13; y++) {
- Accumulate(yuv1 + Y_OFF, BPS, yuv2 + Y_OFF, BPS, x, y, 16, 16, &s);
+ VP8SSIMAccumulate(yuv1 + Y_OFF, BPS, yuv2 + Y_OFF, BPS, x, y, 16, 16, &s);
}
}
for (x = 1; x < 7; x++) {
for (y = 1; y < 7; y++) {
- Accumulate(yuv1 + U_OFF, BPS, yuv2 + U_OFF, BPS, x, y, 8, 8, &s);
- Accumulate(yuv1 + V_OFF, BPS, yuv2 + V_OFF, BPS, x, y, 8, 8, &s);
+ VP8SSIMAccumulate(yuv1 + U_OFF, BPS, yuv2 + U_OFF, BPS, x, y, 8, 8, &s);
+ VP8SSIMAccumulate(yuv1 + V_OFF, BPS, yuv2 + V_OFF, BPS, x, y, 8, 8, &s);
}
}
- return GetSSIM(&s);
+ return VP8SSIMGet(&s);
}
//------------------------------------------------------------------------------
diff --git a/src/enc/picture.c b/src/enc/picture.c
index a4312fb9..3b284d12 100644
--- a/src/enc/picture.c
+++ b/src/enc/picture.c
@@ -11,6 +11,7 @@
#include <assert.h>
#include <stdlib.h>
+#include <math.h>
#include "./vp8enci.h"
@@ -659,7 +660,58 @@ void WebPCleanupTransparentArea(WebPPicture* const pic) {
#undef SIZE2
//------------------------------------------------------------------------------
-// Simplest call:
+// Distortion
+
+// Max value returned in case of exact similarity.
+static const double kMinDistortion_dB = 99.;
+
+int WebPPictureDistortion(const WebPPicture* const pic1,
+ const WebPPicture* const pic2,
+ int type, float result[5]) {
+ int c;
+ DistoStats stats[5];
+
+ if (pic1->width != pic2->width ||
+ pic1->height != pic2->height ||
+ (pic1->a == NULL) != (pic2->a == NULL)) {
+ return 0;
+ }
+
+ memset(stats, 0, sizeof(stats));
+ VP8SSIMAccumulatePlane(pic1->y, pic1->y_stride,
+ pic2->y, pic2->y_stride,
+ pic1->width, pic1->height, &stats[0]);
+ VP8SSIMAccumulatePlane(pic1->u, pic1->uv_stride,
+ pic2->u, pic2->uv_stride,
+ (pic1->width + 1) >> 1, (pic1->height + 1) >> 1,
+ &stats[1]);
+ VP8SSIMAccumulatePlane(pic1->v, pic1->uv_stride,
+ pic2->v, pic2->uv_stride,
+ (pic1->width + 1) >> 1, (pic1->height + 1) >> 1,
+ &stats[2]);
+ if (pic1->a != NULL) {
+ VP8SSIMAccumulatePlane(pic1->a, pic1->a_stride,
+ pic2->a, pic2->a_stride,
+ pic1->width, pic1->height, &stats[3]);
+ }
+ for (c = 0; c <= 4; ++c) {
+ if (type == 1) {
+ const double v = VP8SSIMGet(&stats[c]);
+ result[c] = (v < 1.) ? -10.0 * log10(1. - v)
+ : kMinDistortion_dB;
+ } else {
+ const double v = VP8SSIMGetSquaredError(&stats[c]);
+ result[c] = (v > 0.) ? -4.3429448 * log(v / (255 * 255.))
+ : kMinDistortion_dB;
+ }
+ // Accumulate forward
+ if (c < 4) VP8SSIMAddStats(&stats[c], &stats[4]);
+ }
+ return 1;
+}
+
+//------------------------------------------------------------------------------
+// Simplest high-level calls:
typedef int (*Importer)(WebPPicture* const, const uint8_t* const, int);
diff --git a/src/enc/vp8enci.h b/src/enc/vp8enci.h
index 2689139f..ce8492a5 100644
--- a/src/enc/vp8enci.h
+++ b/src/enc/vp8enci.h
@@ -455,9 +455,20 @@ int VP8EncFinishLayer(VP8Encoder* const enc); // finalize coding
void VP8EncDeleteLayer(VP8Encoder* enc); // reclaim memory
// in filter.c
-extern void VP8InitFilter(VP8EncIterator* const it);
-extern void VP8StoreFilterStats(VP8EncIterator* const it);
-extern void VP8AdjustFilterStrength(VP8EncIterator* const it);
+
+// SSIM utils
+typedef struct { double w, xm, ym, xxm, xym, yym; } DistoStats;
+void VP8SSIMAddStats(const DistoStats* const src, DistoStats* const dst);
+void VP8SSIMAccumulatePlane(const uint8_t* src1, int stride1,
+ const uint8_t* src2, int stride2,
+ int W, int H, DistoStats* const stats);
+double VP8SSIMGet(const DistoStats* const stats);
+double VP8SSIMGetSquaredError(const DistoStats* const stats);
+
+// autofilter
+void VP8InitFilter(VP8EncIterator* const it);
+void VP8StoreFilterStats(VP8EncIterator* const it);
+void VP8AdjustFilterStrength(VP8EncIterator* const it);
//------------------------------------------------------------------------------
diff --git a/src/webp/encode.h b/src/webp/encode.h
index 8dcac2f9..772ac252 100644
--- a/src/webp/encode.h
+++ b/src/webp/encode.h
@@ -248,6 +248,15 @@ WEBP_EXTERN(void) WebPPictureFree(WebPPicture* const picture);
WEBP_EXTERN(int) WebPPictureCopy(const WebPPicture* const src,
WebPPicture* const dst);
+// Compute PSNR or SSIM distortion between two pictures.
+// Result is in dB, stores in result[] in the Y/U/V/Alpha/All order.
+// Returns 0 in case of error (pic1 and pic2 don't have same dimension, ...)
+// Warning: this function is rather CPU-intensive.
+WEBP_EXTERN(int) WebPPictureDistortion(
+ const WebPPicture* const pic1, const WebPPicture* const pic2,
+ int metric_type, // 0 = PSNR, 1 = SSIM
+ float result[5]);
+
// self-crops a picture to the rectangle defined by top/left/width/height.
// Returns 0 in case of memory allocation error, or if the rectangle is
// outside of the source picture.