kc3-lang/brotli/research/draw_diff.cc

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• Hash : 8544ae85
  Author :
  Date : 2018-06-09T11:17:13
  

  Update (#680)
  
   * fix MSVC warnings
   * cleanups

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• research/draw_diff.cc

• /* 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>
  
  #if !defined(CHECK)
  #define CHECK(X) if (!(X)) exit(EXIT_FAILURE);
  #endif
  
  typedef uint8_t* ScanLine;
  typedef ScanLine* Image;
  
  void ReadPGM(FILE* f, Image* 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);
    ScanLine* lines = new ScanLine[*height];
    *image = lines;
    for (int i = *height - 1; i >= 0; --i) {
      ScanLine line = new uint8_t[*width];
      lines[i] = line;
      CHECK(fread(line, 1, *width, f) == *width);
    }
  }
  
  void CalculateDiff(int** diff, Image image1, Image 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, Image image1, Image 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;
    }
  
    Image 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;
  }
  

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