Patent ID: 6049634
Filing Date: 2000-04-11
Classification: G06T,H04N

Abstract:
An image compression device, in which image data corresponding to one image is divided into a plurality of blocks, each of said blocks being subjected to an image compression process, said image compression device being provided with a first quantization table composed of first quantization coefficients for performing said image compression process, said image compression device comprising:a two-dimensional discrete cosine transformation (two-dimensional DCT) processor that performs a two-dimensional DCT on said image data to obtain DCT coefficients for each of said plurality of blocks;a statistical value calculation processor that performs a statistical value calculation process, related to a quantization and a dequantization, on all of said plurality of blocks for every spatial frequency to obtain a statistical value for every spatial frequency;a quantization table generating processor that obtains a second quantization coefficient for every spatial frequency in such a manner that said statistical value becomes a minimum, so that a second quantization table composed of a plurality of said second quantization coefficients is generated; anda compression processor that quantizes said DCT coefficients to obtain quantized DCT coefficients, compresses said quantized DCT coefficients to obtain compressed image data, and records said compressed image data in a recording medium, said compression processor comprising:a determining processor that determines whether said second quantization table is proper or not, said compression processor using said first quantization table for said quantization and then recording said first quantization table in said recording medium when said determining processor determines that said second quantization table is improper, said compression processor using said second quantization table for said quantization and then recording said second quantization table in said recording medium when said determining processor determines that said second quantization table is proper.