Isoluminant Color Halftoning for Generating Pointillistic Tile Images and Photomosaics

We propose a non-photorealistic (NPR) rendering technique for generating mosaic images of which color composition is analogous to the pointillistic paintings. Input images are firstly downsampled. Next, the downsampled image is halftoned in the way where the luminance is preserved while the hue of colors is different between adjacent pixels. Finally, the halftoned image is upsampled to the original size of the input image by pasting patch images to each pixel in the halftoned image with preserving the average color of patches. When patches are geometrical tiles, results are colorful tile images while if the patches are small photographs then the enlarged image yields photomosaics.