This code take a black and white image and convert it black pixels into a list of numbers. These numbers contain the direction of a node in a quadtree, this means that 231 is a reference, for example, to a node in the third level of the tree at the northwest part of the southwest part of the northeast part of the quadtree. Using this list of directions we can create a black and white image that take the directions of the nodes as a guide to built the image pixel by pixel.