1. An image processing method comprising steps: a computing device receiving an original image including a plurality of colors; specifying a number of multiple layers; the computing device assigning one of the plurality of colors of the original image to one of the multiple layers; determining a height value of one of the multiple layers; and the computing device mapping the height value of one of the multiple layers to the original image according to one of the plurality of colors assigned to one of the multiple layers to generate a height image containing a coordinate value and the height value.