In this paper, we propose a technique for automatic generation of pixel art from character images based on color-difference tolerance. Pixel art is one of image expressions for digital images and is based on the pixel level. Character images that are expressed by pixel art are composed of edge lines and a few colors. The proposed technique is for automatically generating pixel art from a photograph where there was only a single object. However, in the conventional method, it is difficult to determine several parameters of edge detection and decrease color for automatic generation of pixel art. In this paper, to create the optimal decreased color image for each target image, we propose a clustering method using a maximum distance algorithm (MDA) based on the human color-difference tolerance. Moreover, the complete automation of making pixel art is achieved by using the result obtained by clustering using the MDA for the threshold decision of the Canny edge detector. As a result, it is shown that several optimum parameters for pixel art are obtained by using the proposed method.