The Research On Digital Halftone

This paper mainly investigates digital halftone algorithm including error diffusion algorithm, ordered dither algorithm and dot diffusion algorithm. The performance of three algorithms is compared and analyzed. The improvement of ordered dither algorithm makes it different with the result of the original algorithm.Digital halftone technology uses some features of the human vision, and converts a continuous image into a binary image with the tools such as mathematics and computer. When looking at an image, human eyes will take a few or more close points as a whole and take the average. Using this feature, when we observe a halftone image, an average gray level in a particular local area is close to the gray level of the corresponding original continuous image, and forms a continuous effect on the whole.Error Diffusion algorithm is a widely used algorithm with better results. This algorithm is mainly used for neighborhood processing. Under the condition of avoid increasing point size, it can provide higher quality for printing, and the generated halftone images have rich gray levels, each pixels in the halftone images are anisotropic.The method can be implemented by thresholding the image pixels according to the predefined scan path (scan path can be line by line or can be customized), the obtained error after thersholding is spread to nonprocessed pixels in the neighborhood in some specific ways.Dot diffusion technology incorporates the two algorithms, and has the merits of both at the same time, so the processed image using dot diffusion doesn't have artifacts as error diffusion algorithm does, and doesn't makes people feel image special curt as ordered dither algorithm does. The produced results using dot diffusion is clearer than the results using ordered dither algorithm. In practical applications, the printing effect using dot diffusion algorithm is significantly better than error diffusion algorithm and ordered dither algorithm.