IMAGE DATA CODING APPARATUS

An image data coding apparatus adopting the method of this invention includes a divider section for dividing an image having gray levels into a plurality of blocks, each consisting of a plurality of pixels; a pre-processing section for detecting the density and the presence/absence of an edge in an image of each divided block; and a vector quantizing section for encoding an image of each block in accordance with the detected density and the presence/absence of the edge in the image of the block. The pre-processing section detects a standard deviation of density levels of the pixels included in each block. The vector quantizing section divides the density levels of the pixels included in each block into a plurality of level sections so as to obtain a code indicating the level section in which the density level of each pixel is included. In the vector quantizing section, the obtained code is again encoded by means of vector quantization.