11 #define ESCAPE_LIMIT (NUM_SYMS - 1)
15 unsigned char pix1[WIDTH * HEIGHT], pix2[WIDTH * HEIGHT];
17 void readpix(unsigned char *ptr, const char *filename)
19 FILE *fp = fopen(filename, "rb");
25 fseek(fp, 0, SEEK_END);
27 assert(len >= WIDTH * HEIGHT);
28 fseek(fp, len - WIDTH * HEIGHT, SEEK_SET);
30 fread(ptr, 1, WIDTH * HEIGHT, fp);
34 /****************************************************************************
35 * structural similarity metric
36 ****************************************************************************/
37 static void ssim_4x4x2_core( const uint8_t *pix1, intptr_t stride1,
38 const uint8_t *pix2, intptr_t stride2,
41 for( int z = 0; z < 2; z++ )
43 uint32_t s1 = 0, s2 = 0, ss = 0, s12 = 0;
44 for( int y = 0; y < 4; y++ )
45 for( int x = 0; x < 4; x++ )
47 int a = pix1[x+y*stride1];
48 int b = pix2[x+y*stride2];
66 static float ssim_end1( int s1, int s2, int ss, int s12 )
68 /* Maximum value for 10-bit is: ss*64 = (2^10-1)^2*16*4*64 = 4286582784, which will overflow in some cases.
69 * s1*s1, s2*s2, and s1*s2 also obtain this value for edge cases: ((2^10-1)*16*4)^2 = 4286582784.
70 * Maximum value for 9-bit is: ss*64 = (2^9-1)^2*16*4*64 = 1069551616, which will not overflow. */
72 static const int ssim_c1 = (int)(.01*.01*PIXEL_MAX*PIXEL_MAX*64 + .5);
73 static const int ssim_c2 = (int)(.03*.03*PIXEL_MAX*PIXEL_MAX*64*63 + .5);
78 type vars = fss*64 - fs1*fs1 - fs2*fs2;
79 type covar = fs12*64 - fs1*fs2;
80 return (float)(2*fs1*fs2 + ssim_c1) * (float)(2*covar + ssim_c2)
81 / ((float)(fs1*fs1 + fs2*fs2 + ssim_c1) * (float)(vars + ssim_c2));
85 static float ssim_end4( int sum0[5][4], int sum1[5][4], int width )
88 for( int i = 0; i < width; i++ )
89 ssim += ssim_end1( sum0[i][0] + sum0[i+1][0] + sum1[i][0] + sum1[i+1][0],
90 sum0[i][1] + sum0[i+1][1] + sum1[i][1] + sum1[i+1][1],
91 sum0[i][2] + sum0[i+1][2] + sum1[i][2] + sum1[i+1][2],
92 sum0[i][3] + sum0[i+1][3] + sum1[i][3] + sum1[i+1][3] );
96 float x264_pixel_ssim_wxh(
97 uint8_t *pix1, intptr_t stride1,
98 uint8_t *pix2, intptr_t stride2,
99 int width, int height, void * buf, int *cnt )
103 int (*sum0)[4] = buf;
104 int (*sum1)[4] = sum0 + (width >> 2) + 3;
107 for( int y = 1; y < height; y++ )
112 for( int x = 0; x < width; x+=2 )
113 ssim_4x4x2_core( &pix1[4*(x+z*stride1)], stride1, &pix2[4*(x+z*stride2)], stride2, &sum0[x] );
115 for( int x = 0; x < width-1; x += 4 )
116 ssim += ssim_end4( sum0+x, sum1+x, min(4,width-x-1) );
118 *cnt = (height-1) * (width-1);
122 int main(int argc, char **argv)
124 readpix(pix1, argv[1]);
125 readpix(pix2, argv[2]);
127 double sum_sq_err = 0.0;
129 for (unsigned y = 0; y < HEIGHT; ++y) {
130 for (unsigned x = 0; x < WIDTH; ++x) {
131 int k1 = pix1[y * WIDTH + x];
132 int k2 = pix2[y * WIDTH + x];
133 sum_sq_err += (k1 - k2) * (k1 - k2);
136 double mse = sum_sq_err / double(WIDTH * HEIGHT);
137 double psnr_db = 20 * log10(255.0 / sqrt(mse));
139 void *scratch = new int[8 * WIDTH];
141 float ssim = x264_pixel_ssim_wxh(
142 pix1 + 2 + WIDTH*2, WIDTH,
143 pix2 + 2 + WIDTH*2, WIDTH,
144 WIDTH - 2, HEIGHT - 2, scratch, &cnt);
147 printf("%.2f %.2f\n", psnr_db, -10.0 * log10(1 - ssim));