blob: 01b671651bb05e015dafa58f1f81b72ade57ba23 [file] [log] [blame]
/* Copyright 2016 Google Inc. All Rights Reserved.
Author: zip753@gmail.com (Ivan Nikulin)
Distributed under MIT license.
See file LICENSE for detail or copy at https://opensource.org/licenses/MIT
*/
/* Tool for drawing diff PPM images between two input PGM images. Normally used
with backward reference histogram drawing tool. */
#include <algorithm>
#include <cassert>
#include <cmath>
#include <cstdint>
#include <cstdio>
#include <cstdlib> /* exit, EXIT_FAILURE */
#include <vector>
#ifndef CHECK
#define CHECK(X) if (!(X)) exit(EXIT_FAILURE);
#endif
void ReadPGM(FILE* f, uint8_t*** image, size_t* height, size_t* width) {
int colors;
CHECK(fscanf(f, "P5\n%lu %lu\n%d\n", width, height, &colors) == 3);
assert(colors == 255);
*image = new uint8_t*[*height];
for (int i = *height - 1; i >= 0; --i) {
(*image)[i] = new uint8_t[*width];
CHECK(fread((*image)[i], 1, *width, f) == *width);
}
}
void CalculateDiff(int** diff, uint8_t** image1, uint8_t** image2,
size_t height, size_t width) {
for (size_t i = 0; i < height; ++i) {
for (size_t j = 0; j < width; ++j) {
diff[i][j] = static_cast<int>(image1[i][j]) - image2[i][j];
}
}
}
void DrawDiff(int** diff, uint8_t** image1, uint8_t** image2,
size_t height, size_t width, FILE* f) {
int max = -1234;
int min = +1234;
for (size_t i = 0; i < height; ++i) {
for (size_t j = 0; j < width; ++j) {
if (max < diff[i][j]) max = diff[i][j];
if (min > diff[i][j]) min = diff[i][j];
int img_min = std::min(255 - image1[i][j], 255 - image2[i][j]);
if (max < img_min) max = img_min;
}
}
int abs_max = -min;
if (abs_max < max) abs_max = max;
fprintf(f, "P6\n%lu %lu\n%d\n", width, height, abs_max);
uint8_t* row = new uint8_t[3 * width];
for (int i = height - 1; i >= 0; --i) {
for (int j = 0; j < width; ++j) {
int min_val = std::min(255 - image1[i][j], 255 - image2[i][j]);
int max_val = std::max(min_val, abs(diff[i][j]));
if (diff[i][j] > 0) { /* red */
row[3 * j + 0] = abs_max - max_val + diff[i][j];
row[3 * j + 1] = abs_max - max_val;
row[3 * j + 2] = abs_max - max_val + min_val;
} else { /* green */
row[3 * j + 0] = abs_max - max_val;
row[3 * j + 1] = abs_max - max_val - diff[i][j];
row[3 * j + 2] = abs_max - max_val + min_val;
}
}
fwrite(row, 1, 3 * width, f);
}
delete[] row;
}
int main(int argc, char* argv[]) {
if (argc != 4) {
printf("usage: %s pgm1 pgm2 diff_ppm_path\n", argv[0]);
return 1;
}
uint8_t **image1, **image2;
size_t h1, w1, h2, w2;
FILE* fimage1 = fopen(argv[1], "rb");
ReadPGM(fimage1, &image1, &h1, &w1);
fclose(fimage1);
FILE* fimage2 = fopen(argv[2], "rb");
ReadPGM(fimage2, &image2, &h2, &w2);
fclose(fimage2);
if (!(h1 == h2 && w1 == w2)) {
printf("Images must have the same size.\n");
return 1;
}
int** diff = new int*[h1];
for (size_t i = 0; i < h1; ++i) diff[i] = new int[w1];
CalculateDiff(diff, image1, image2, h1, w1);
FILE* fdiff = fopen(argv[3], "wb");
DrawDiff(diff, image1, image2, h1, w1, fdiff);
fclose(fdiff);
return 0;
}