code: public void getDescriptorsInRegion(int pixelX0 , int pixelY0 , int pixelX1 , int pixelY1 ,
  									   List<TupleDesc_F64> output ) {
  		int gridX0 = (int)Math.ceil(pixelX0/(double) pixelsPerCell);
  		int gridY0 = (int)Math.ceil(pixelY0/(double) pixelsPerCell);
  
  		int gridX1 = pixelX1/ pixelsPerCell - cellsPerBlockX;
  		int gridY1 = pixelY1/ pixelsPerCell - cellsPerBlockY;
  
  		for (int y = gridY0; y <= gridY1; y++) {
  			int index = y*cellCols + gridX0;
  			for (int x = gridX0; x <= gridX1; x++ ) {
  				output.add( descriptions.get(index++) );
  			}
  		}
  	}
docs: Convenience function which returns a list of all the descriptors computed inside the specified region in the image
  
  @param pixelX0 Pixel coordinate X-axis lower extent
  @param pixelY0 Pixel coordinate Y-axis lower extent
  @param pixelX1 Pixel coordinate X-axis upper extent
  @param pixelY1 Pixel coordinate Y-axis upper extent
  @param output List of descriptions