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