// Copyright 2016 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.

// -----------------------------------------------------------------------------

//

// Simple tool to load two webp/png/jpg/tiff files and compute PSNR/SSIM.

// This is mostly a wrapper around WebPPictureDistortion().

//

/*

gcc -o get_disto get_disto.c -O3 -I../ -L../examples -L../imageio \

-lexample_util -limageio_util -limagedec -lwebp -L/opt/local/lib \

-lpng -lz -ljpeg -ltiff -lm -lpthread

*/

//

// Author: Skal (pascal.massimino@gmail.com)

#include <assert.h>

#include <stdio.h>

#include <stdlib.h>

#include <string.h>

#include "webp/encode.h"

#include "imageio/image_dec.h"

#include "imageio/imageio_util.h"

static size_t ReadPicture(const char* const filename, WebPPicture* const pic,

int keep_alpha) {

const uint8_t* data = NULL;

size_t data_size = 0;

WebPImageReader reader = NULL;

int ok = ImgIoUtilReadFile(filename, &data, &data_size);

if (!ok) goto End;

pic->use_argb = 1; // force ARGB

#ifdef HAVE_WINCODEC_H

// Try to decode the file using WIC falling back to the other readers for

// e.g., WebP.

ok = ReadPictureWithWIC(filename, pic, keep_alpha, NULL);

if (ok) goto End;

#endif

reader = WebPGuessImageReader(data, data_size);

ok = reader(data, data_size, pic, keep_alpha, NULL);

End:

if (!ok) {

fprintf(stderr, "Error! Could not process file %s\n", filename);

}

free((void*)data);

return ok ? data_size : 0;

}

static void RescalePlane(uint8_t* plane, int width, int height,

int x_stride, int y_stride, int max) {

const uint32_t factor = (max > 0) ? (255u << 16) / max : 0;

int x, y;

for (y = 0; y < height; ++y) {

uint8_t* const ptr = plane + y * y_stride;

for (x = 0; x < width * x_stride; x += x_stride) {

const uint32_t diff = (ptr[x] * factor + (1 << 15)) >> 16;

ptr[x] = diff;

}

}

}

// Return the max absolute difference.

static int DiffScaleChannel(uint8_t* src1, int stride1,

const uint8_t* src2, int stride2,

int x_stride, int w, int h, int do_scaling) {

int x, y;

int max = 0;

for (y = 0; y < h; ++y) {

uint8_t* const ptr1 = src1 + y * stride1;

const uint8_t* const ptr2 = src2 + y * stride2;

for (x = 0; x < w * x_stride; x += x_stride) {

const int diff = abs(ptr1[x] - ptr2[x]);

if (diff > max) max = diff;

ptr1[x] = diff;

}

}

if (do_scaling) RescalePlane(src1, w, h, x_stride, stride1, max);

return max;

}

//------------------------------------------------------------------------------

// SSIM calculation. We re-implement these functions here, out of dsp/, to avoid

// breaking the library's hidden visibility. This code duplication avoids the

// bigger annoyance of having to open up internal details of libdsp...

#define SSIM_KERNEL 3 // total size of the kernel: 2 * SSIM_KERNEL + 1

// struct for accumulating statistical moments

typedef struct {

uint32_t w; // sum(w_i) : sum of weights

uint32_t xm, ym; // sum(w_i * x_i), sum(w_i * y_i)

uint32_t xxm, xym, yym; // sum(w_i * x_i * x_i), etc.

} DistoStats;

// hat-shaped filter. Sum of coefficients is equal to 16.

static const uint32_t kWeight[2 * SSIM_KERNEL + 1] = { 1, 2, 3, 4, 3, 2, 1 };

static WEBP_INLINE double SSIMCalculation(const DistoStats* const stats) {

const uint32_t N = stats->w;

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

}

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);

}

// Compute SSIM-score map. Return -1 in case of error, max diff otherwise.

static int SSIMScaleChannel(uint8_t* src1, int stride1,

const uint8_t* src2, int stride2,

int x_stride, int w, int h, int do_scaling) {

int x, y;

int max = 0;

uint8_t* const plane1 = (uint8_t*)malloc(2 * w * h * sizeof(*plane1));

uint8_t* const plane2 = plane1 + w * h;

if (plane1 == NULL) return -1;

// extract plane

for (y = 0; y < h; ++y) {

for (x = 0; x < w; ++x) {

plane1[x + y * w] = src1[x * x_stride + y * stride1];

plane2[x + y * w] = src2[x * x_stride + y * stride2];

}

}

for (y = 0; y < h; ++y) {

for (x = 0; x < w; ++x) {

const double ssim = SSIMGetClipped(plane1, w, plane2, w, x, y, w, h);

int diff = (int)(255 * (1. - ssim));

if (diff < 0) {

diff = 0;

} else if (diff > max) {

max = diff;

}

src1[x * x_stride + y * stride1] = (diff > 255) ? 255u : (uint8_t)diff;

}

}

free(plane1);

if (do_scaling) RescalePlane(src1, w, h, x_stride, stride1, max);

return max;

}

// Convert an argb picture to luminance.

static void ConvertToGray(WebPPicture* const pic) {

int x, y;

assert(pic != NULL);

assert(pic->use_argb);

for (y = 0; y < pic->height; ++y) {

uint32_t* const row = &pic->argb[y * pic->argb_stride];

for (x = 0; x < pic->width; ++x) {

const uint32_t argb = row[x];

const uint32_t r = (argb >> 16) & 0xff;

const uint32_t g = (argb >> 8) & 0xff;

const uint32_t b = (argb >> 0) & 0xff;

// We use BT.709 for converting to luminance.

const uint32_t Y = (uint32_t)(0.2126 * r + 0.7152 * g + 0.0722 * b + .5);

row[x] = (argb & 0xff000000u) | (Y * 0x010101u);

}

}

}

static void Help(void) {

fprintf(stderr,

"Usage: get_disto [-ssim][-psnr][-alpha] compressed.webp orig.webp\n"

" -ssim ..... print SSIM distortion\n"

" -psnr ..... print PSNR distortion (default)\n"

" -alpha .... preserve alpha plane\n"

" -h ........ this message\n"

" -o <file> . save the diff map as a WebP lossless file\n"

" -scale .... scale the difference map to fit [0..255] range\n"

" -gray ..... use grayscale for difference map (-scale)\n"

" Also handles PNG, JPG and TIFF files, in addition to WebP.\n");

}

int main(int argc, const char *argv[]) {

WebPPicture pic1, pic2;

size_t size1 = 0, size2 = 0;

int ret = 1;

float disto[5];

int type = 0;

int c;

int help = 0;

int keep_alpha = 0;

int scale = 0;

int use_gray = 0;

const char* name1 = NULL;

const char* name2 = NULL;

const char* output = NULL;

if (!WebPPictureInit(&pic1) || !WebPPictureInit(&pic2)) {

fprintf(stderr, "Can't init pictures\n");

return 1;

}

for (c = 1; c < argc; ++c) {

if (!strcmp(argv[c], "-ssim")) {

type = 1;

} else if (!strcmp(argv[c], "-psnr")) {

type = 0;

} else if (!strcmp(argv[c], "-alpha")) {

keep_alpha = 1;

} else if (!strcmp(argv[c], "-scale")) {

scale = 1;

} else if (!strcmp(argv[c], "-gray")) {

use_gray = 1;

} else if (!strcmp(argv[c], "-h")) {

help = 1;

ret = 0;

} else if (!strcmp(argv[c], "-o")) {

if (++c == argc) {

fprintf(stderr, "missing file name after %s option.\n", argv[c - 1]);

goto End;

}

output = argv[c];

} else if (name1 == NULL) {

name1 = argv[c];

} else {

name2 = argv[c];

}

}

if (help || name1 == NULL || name2 == NULL) {

if (!help) {

fprintf(stderr, "Error: missing arguments.\n");

}

Help();

goto End;

}

size1 = ReadPicture(name1, &pic1, 1);

size2 = ReadPicture(name2, &pic2, 1);

if (size1 == 0 || size2 == 0) goto End;

if (!keep_alpha) {

WebPBlendAlpha(&pic1, 0x00000000);

WebPBlendAlpha(&pic2, 0x00000000);

}

if (!WebPPictureDistortion(&pic1, &pic2, type, disto)) {

fprintf(stderr, "Error while computing the distortion.\n");

goto End;

}

printf("%u %.2f %.2f %.2f %.2f %.2f [ %.2f bpp ]\n",

(unsigned int)size1,

disto[4], disto[0], disto[1], disto[2], disto[3],

8.f * size1 / pic1.width / pic1.height);

if (output != NULL) {

uint8_t* data = NULL;

size_t data_size = 0;

if (pic1.use_argb != pic2.use_argb) {

fprintf(stderr, "Pictures are not in the same argb format. "

"Can't save the difference map.\n");

goto End;

}

if (pic1.use_argb) {

int n;

fprintf(stderr, "max differences per channel: ");

for (n = 0; n < 3; ++n) { // skip the alpha channel

const int range = (type == 1) ?

SSIMScaleChannel((uint8_t*)pic1.argb + n, pic1.argb_stride * 4,

(const uint8_t*)pic2.argb + n, pic2.argb_stride * 4,

4, pic1.width, pic1.height, scale) :

DiffScaleChannel((uint8_t*)pic1.argb + n, pic1.argb_stride * 4,

(const uint8_t*)pic2.argb + n, pic2.argb_stride * 4,

4, pic1.width, pic1.height, scale);

if (range < 0) fprintf(stderr, "\nError computing diff map\n");

fprintf(stderr, "[%d]", range);

}

fprintf(stderr, "\n");

if (use_gray) ConvertToGray(&pic1);

} else {

fprintf(stderr, "Can only compute the difference map in ARGB format.\n");

goto End;

}

#if !defined(WEBP_REDUCE_CSP)

data_size = WebPEncodeLosslessBGRA((const uint8_t*)pic1.argb,

pic1.width, pic1.height,

pic1.argb_stride * 4,

&data);

if (data_size == 0) {

fprintf(stderr, "Error during lossless encoding.\n");

goto End;

}

ret = ImgIoUtilWriteFile(output, data, data_size) ? 0 : 1;

WebPFree(data);

if (ret) goto End;

#else

(void)data;

(void)data_size;

fprintf(stderr, "Cannot save the difference map. Please recompile "

"without the WEBP_REDUCE_CSP flag.\n");

#endif // WEBP_REDUCE_CSP

}

ret = 0;

End:

WebPPictureFree(&pic1);

WebPPictureFree(&pic2);

return ret;

}