Two Channel Image Coding Scheme
Diego P. de Garrido, Paulo Roberto Rosa Lopes Nunes, Jacques Szczupak · Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE · 1989
In this paper we present a two channel image compression technique which allows good compression rates and image quality. The technique consists in splitting the image into two parts: a low-pass one, which represents the general area brightness without sharp contours, and the high-pass part containing mainly sharp edge information. This decomposition into low and high-frequency components was first presented in the so called Synthetic High System. The Synthetic Highs System exploits elegantly the properties of the visual system and consists in detecting and coding edges separately from low frequency components. The method proposed here follows the general idea of the Synthetic Highs System, though there is no edge-detection involved. Most of the contribution of our scheme relates to the way the two frequency bands are coded: transform coding for the low-pass part and vector quantization for the high-pass one. The system was tested using several monochromatic images with sizes 256 x 256 and 512 x 512; good results were obtained in terms of visual quality and peak signal-to-noise ratio. Blocking effects were not observed for the images tested.