Pyramidal image compression using anisotropic and error-corrected interpolation

In pyramidal coding, the key to significant bit rate reduction is the reduction of interpolation error. This is usually accomplished through well-designed nonlinear interpolation filters, such as median and morphological filters. These filters are usually isotropic, hence cannot account for the anisotropic nature of the images. In addition, these filters base their interpolation solely on the image at the immediate higher level (lower resolution), hence a smaller interpolation error can be expected if the already-transmitted error signals are used for the interpolation of the remaining pixels. In view of these two problems, this paper proposes to decrease the interpolation error through the introduction of anisotropic techniques and the use of the transmitted error signals to improve the interpolation of the remaining pixels. This error is further reduced through the usage of anisotropic diffusion as the low-pass filter. Finally, an anisotropic DPCM coder is presented to code the image at the top of the pyramid.