Patent ID: 6643402
Filing Date: 2003-11-04
Classification: H04N

Abstract:
An image compression device for compressing image data comprising:a discrete cosine transformation circuit performing a two-dimensional discrete cosine transformation on,.image data constituting an image of one screen to generate a discrete cosine transformation coefficient; a quantization circuit quantizing the discrete cosine transformation coefficient supplied from said discrete cosine transformation circuit referring to a quantization threshold value stored in a preset quantization table; a Huffman encoding circuit performing a variable length encoding on the discrete cosine transformation coefficient quantized in said quantization circuit, referring to a Huffman code stored in a preset Huffman table to generate compression image data; a code amount counter counting a code amount of the compression image data generated by said Huffman encoding circuit; and a control circuit repeatedly performing a compression process by said discrete cosine transformation circuit, said quantization circuit and said Huffman encoding circuit, while changing a setting of a parameter constituted of said quantizaiton threshold value and said Huffman code until the code amount of the compression image data counted by said code amount counter becomes equal to or smaller than a predetermined value, to determine an optimal version of said parameter for rendering the code amount of the compression image data equal to or smaller than the predetermined value; wherein said control circuit dividing said image of one screen into a plurality of blocks, selecting a block from said plurality of blocks while changing the number of blocks to be selected, and repeating said compression process on image data of the selected block to determine said optimal version of said parameter.