Recent Results in High Compression Image Coding

The digital representation of an image requires a very large number of bits. The goal of image coding is to reduce this number as much as possible, and to reconstruct a faithful duplicate of the original picture. Early efforts in image coding, solely guided by information theory, led to a plethora of methods. The compression ratio reached a plateau of about 10:1 several years ago. Recent progress in the study of the brain mechanism of vision and of scene analysis has opened new vistas in picture coding. The concept of directional sensitivity of neurones in the visual cortex combined with the separate processing of contours and textures has led to a new class of coding methods, called second generation, capable of achieving compression ratios as high as 100:1. In this paper, recent results on object-based coding methods are reported, exhibiting improvements in the previous second-generation methods.