static IImageRegion g22_mostOverlappingRegionInOtherImage(IImageRegion region, IImageRegions regions2) {
  WidthAndHeight image1 = region.image();
  WidthAndHeight image2 = regions2.image();
  assertSameSize(image1, image2);
  
  // pixel positions in image 1 region
  int[] pixels = region.pixelsAsIntArray();
  
  // region matrix of image 2
  int[] regionMatrix = regions2.regionMatrix();
  
  // count matching pixels for each image 2 region
  int nRegions = regions2.nRegions();
  int[] counts = new[nRegions+1];
  
  for (pos : pixels)
    counts[regionMatrix[pos]]++;
    
  ret regions2.getRegion(indexOfHighest(counts));
}