1 /* Copyright 2016 Google Inc. All Rights Reserved. 2 Author: zip753 (at) gmail.com (Ivan Nikulin) 3 4 Distributed under MIT license. 5 See file LICENSE for detail or copy at https://opensource.org/licenses/MIT 6 */ 7 8 /* Tool for drawing diff PPM images between two input PGM images. Normally used 9 with backward reference histogram drawing tool. */ 10 11 #include <algorithm> 12 #include <cassert> 13 #include <cmath> 14 #include <cstdint> 15 #include <cstdio> 16 #include <cstdlib> /* exit, EXIT_FAILURE */ 17 #include <vector> 18 19 #ifndef CHECK 20 #define CHECK(X) if (!(X)) exit(EXIT_FAILURE); 21 #endif 22 23 void ReadPGM(FILE* f, uint8_t*** image, size_t* height, size_t* width) { 24 int colors; 25 CHECK(fscanf(f, "P5\n%lu %lu\n%d\n", width, height, &colors) == 3); 26 assert(colors == 255); 27 *image = new uint8_t*[*height]; 28 for (int i = *height - 1; i >= 0; --i) { 29 (*image)[i] = new uint8_t[*width]; 30 CHECK(fread((*image)[i], 1, *width, f) == *width); 31 } 32 } 33 34 void CalculateDiff(int** diff, uint8_t** image1, uint8_t** image2, 35 size_t height, size_t width) { 36 for (size_t i = 0; i < height; ++i) { 37 for (size_t j = 0; j < width; ++j) { 38 diff[i][j] = static_cast<int>(image1[i][j]) - image2[i][j]; 39 } 40 } 41 } 42 43 void DrawDiff(int** diff, uint8_t** image1, uint8_t** image2, 44 size_t height, size_t width, FILE* f) { 45 int max = -1234; 46 int min = +1234; 47 for (size_t i = 0; i < height; ++i) { 48 for (size_t j = 0; j < width; ++j) { 49 if (max < diff[i][j]) max = diff[i][j]; 50 if (min > diff[i][j]) min = diff[i][j]; 51 int img_min = std::min(255 - image1[i][j], 255 - image2[i][j]); 52 if (max < img_min) max = img_min; 53 } 54 } 55 56 int abs_max = -min; 57 if (abs_max < max) abs_max = max; 58 59 fprintf(f, "P6\n%lu %lu\n%d\n", width, height, abs_max); 60 61 uint8_t* row = new uint8_t[3 * width]; 62 for (int i = height - 1; i >= 0; --i) { 63 for (int j = 0; j < width; ++j) { 64 int min_val = std::min(255 - image1[i][j], 255 - image2[i][j]); 65 int max_val = std::max(min_val, abs(diff[i][j])); 66 if (diff[i][j] > 0) { /* red */ 67 row[3 * j + 0] = abs_max - max_val + diff[i][j]; 68 row[3 * j + 1] = abs_max - max_val; 69 row[3 * j + 2] = abs_max - max_val + min_val; 70 } else { /* green */ 71 row[3 * j + 0] = abs_max - max_val; 72 row[3 * j + 1] = abs_max - max_val - diff[i][j]; 73 row[3 * j + 2] = abs_max - max_val + min_val; 74 } 75 } 76 fwrite(row, 1, 3 * width, f); 77 } 78 delete[] row; 79 } 80 81 int main(int argc, char* argv[]) { 82 if (argc != 4) { 83 printf("usage: %s pgm1 pgm2 diff_ppm_path\n", argv[0]); 84 return 1; 85 } 86 87 uint8_t **image1, **image2; 88 size_t h1, w1, h2, w2; 89 90 FILE* fimage1 = fopen(argv[1], "rb"); 91 ReadPGM(fimage1, &image1, &h1, &w1); 92 fclose(fimage1); 93 94 FILE* fimage2 = fopen(argv[2], "rb"); 95 ReadPGM(fimage2, &image2, &h2, &w2); 96 fclose(fimage2); 97 98 if (!(h1 == h2 && w1 == w2)) { 99 printf("Images must have the same size.\n"); 100 return 1; 101 } 102 103 int** diff = new int*[h1]; 104 for (size_t i = 0; i < h1; ++i) diff[i] = new int[w1]; 105 CalculateDiff(diff, image1, image2, h1, w1); 106 107 FILE* fdiff = fopen(argv[3], "wb"); 108 DrawDiff(diff, image1, image2, h1, w1, fdiff); 109 fclose(fdiff); 110 111 return 0; 112 } 113
