DITHERED IMAGE COMPRESSION SYSTEM

A dithered image compression system that converts a source image into an image that is efficiently compressed and yet preserves the visual image information of the original source image in a computer environment. A preferred embodiment of the invention removes the image data from the source image that are lost during the normal storage and halftoning stages in one step. Each pixel in the source image is compared to the threshold array values. If the value of the source image pixel is less than the corresponding threshold array pixel, then a zero is placed in that position in the dithered image array, otherwise a one is placed in the dithered image array. The dithered image array is then compared with the threshold array, thereby creating a range array where the range of each pixel is determined using the dithered image array values combined with the threshold array values. A value selection is then made from the range array to create a derived image array where one value is selected from the range that has been established for each pixel. The actual value selected depends on the desired print quality and/or compression ratio. The result is an image that is much simpler than the source image and can be compressed without any further loss of information because the amount of data known to be lost has been removed. The derived image will produce the same dithered image using the same threshold array as the original source image in the halftone process.