Digital Halftoning Using Error Diffusion and Linear Pixel Shuffling

Digital halftoning is used to render continuous gray-scale images to a device, such as a laser printer or video display, that is only capable of binary output (black and white). Other applications include image transmission and storage where the gray-scale to binary data reduction translates to reduced transmission and storage costs. The idea is that the local density of dots mimics the original gray-scale and appears nearly the same to a viewer. This method works because the human visual system acts like an averaging or low-pass filtering device when presented with the relatively high frequency dot pattern. The challenge is to optimize the appearance by minimizing side effects such as undesirable texture artifacts and false contours, that can be produced by the pattern. The general issues that must be addressed are those concerned with the original image relative to dynamic range and spatial resolution of the grayscale and those concerned with the visibility of the halftone pattern.