Halftoning for color-indexed displays

In many applications, the color bit-depth of an image has to be modified, typically lowered, to match the rendering device. Halftoning is typically used to reduce the effects of quantization, which can produce objectionable contouring effects. Until now, color-indexed images whose palette was a subset of the colors of the image could only be dithered using error diffusion. We present an algorithm for color halftoning when the color palette is image-dependent. Experimental results demonstrate that our new algorithm does not introduce color shifts, color spikes, or wormy textures, and has greater preservation of detail