srecord noeq HashBinaryImage(IBinaryImage img) {
  long hash;
  
  long get() {
    if (img == null) ret hash;
    var img = this.img.toImage2B();
    
    int w = img.getWidth(), h = img.getHeight();
    int n = w*h;
    byte[] pixels = img.pixels;

    addToHash(w);
    addToHash(h);
    
    for i to n:
      addToHash((pixels[i/8] & (1 << (i & 7))) != 0 ? 0xFFFFFFFF : 0xFF000000);

    ret hash;
  }
  
  void addToHash(long x) {
    hash = boostHashCombine64(hash, x);
  }
}