Perceptually based coding of monochrome and color still images

The authors describe a human visual perception approach and report some results for this problem. The approach is based on the differential quantization of images, in which smooth approximations are subtracted from the image prior to quantization. They consider two such approximations. The first one is an approximation by splines obtained from a sparse and fixed subsampled array of the image. The second one segments the image into piecewise constant regions on the basis of the local activity of the image. Both these approximations result in remainders of residual images where large errors are localized in portions of the image of high activity. Because of visual masking the remainder image can now be coarsely quantized without visual impairment to the reconstructed image. The coarsely quantized remainder is now encoded in an error free manner. In such a perceptually based encoding method the mean square error is now dependent on the activity of the image.<>