code: void selectBlockSize( int width , int height , int requestedBlockWidth) {
  
  		if( height < requestedBlockWidth ) {
  			blockHeight = height;
  		} else {
  			int rows = height/requestedBlockWidth;
  			blockHeight = height/rows;
  		}
  
  		if( width < requestedBlockWidth ) {
  			blockWidth = width;
  		} else {
  			int cols = width/requestedBlockWidth;
  			blockWidth = width/cols;
  		}
  	}
docs: Selects a block size which is close to the requested block size by the user