Method and apparatus for coding image information, and method of creating code books

DETAILED DESCRIPTION Accordingly, an object of the present invention is to provide an image information coding apparatus which utilizes the correlativity of image data to perform vector quantization of high image quality with a comparatively small look-up table.
According to the present invention, the foregoing objects are attained by providing a color image coding apparatus which includes extracting means for extracting frequency components every block composed of a plurality of pixels, dividing means for dividing the block into a plurality of sub-blocks in dependence upon the frequency components extracted by the extracting means, first quantizing means for performing vector quantization on every sub-block, and second quantizing means for performing further vector quantization in dependence upon correlation among the sub-blocks using results of quantization performed by the first quantizing means.
Another object of the present invention is to provide a coding apparatus in which a pixel block is divided into a plurality of sub-blocks and vector quantization is performed independently sub-block by sub-block, whereby the number of vector dimensions can be reduced and memory capacity diminished so as to enable a LUT or the like to be used.
According to the present invention, the foregoing objects are attained by providing a coding apparatus for vector-quantizing digital image information in block units, characterized by comprising dividing means for dividing a plurality of components constituting a pixel block into a plurality of sub-blocks, scalar quantizing means for scalar-quantizing the components of the sub-blocks, first vector quantizing means for vector-quantizing sub-blocks scalar-quantized by the first scalar quantizing means, and second quantizing means for performing further vector quantization in dependence upon correlation among the sub-blocks using results of quantization performed by the first vector quantizing means.
Still another object of the present invention is to provide a coding method and apparatus in which vector quantization is arranged to take place in a number of stages to solve the problems related to processing speed, coding efficiency and circuit size encountered in the conventional methods using an arithmetic unit or look-up table