8 /* Tool for drawing diff PPM images between two input PGM images. Normally used
28   for (int i = *height - 1; i >= 0; --i) {  in ReadPGM()
34 void CalculateDiff(int** diff, uint8_t** image1, uint8_t** image2,  in CalculateDiff()  argument
38       diff[i][j] = static_cast<int>(image1[i][j]) - image2[i][j];  in CalculateDiff()
43 void DrawDiff(int** diff, uint8_t** image1, uint8_t** image2,  in DrawDiff()  argument
45   int max = -1234;  in DrawDiff()
49       if (max < diff[i][j]) max = diff[i][j];  in DrawDiff()
50       if (min > diff[i][j]) min = diff[i][j];  in DrawDiff()
51       int img_min = std::min(255 - image1[i][j], 255 - image2[i][j]);  in DrawDiff()
56   int abs_max = -min;  in DrawDiff()
62   for (int i = height - 1; i >= 0; --i) {  in DrawDiff()
64       int min_val = std::min(255 - image1[i][j], 255 - image2[i][j]);  in DrawDiff()
65       int max_val = std::max(min_val, abs(diff[i][j]));  in DrawDiff()
66       if (diff[i][j] > 0) { /* red */  in DrawDiff()
67         row[3 * j + 0] = abs_max - max_val + diff[i][j];  in DrawDiff()
68         row[3 * j + 1] = abs_max - max_val;  in DrawDiff()
69         row[3 * j + 2] = abs_max - max_val + min_val;  in DrawDiff()
71         row[3 * j + 0] = abs_max - max_val;  in DrawDiff()
72         row[3 * j + 1] = abs_max - max_val - diff[i][j];  in DrawDiff()
73         row[3 * j + 2] = abs_max - max_val + min_val;  in DrawDiff()
103   int** diff = new int*[h1];  in main()  local
104   for (size_t i = 0; i < h1; ++i) diff[i] = new int[w1];  in main()
105   CalculateDiff(diff, image1, image2, h1, w1);  in main()
108   DrawDiff(diff, image1, image2, h1, w1, fdiff);  in main()