IMAGE CODING APPARATUS, IMAGE DECODING APPARATUS, IMAGE CODING METHOD, IMAGE DECODING METHOD, AND PROGRAM FOR THEM

摘要

PROBLEM TO BE SOLVED: To provide an image coding apparatus capable of compressing a dot image at a high compression rate by preventing the image quality of the dot image from being deteriorated. SOLUTION: A raster generating section 400 in the image coding apparatus converts input image data to each color component image. A representative symbol generating section 402 extracts a dot pattern included in a received color component image as a symbol, applies clustering to the extracted symbol by using, e.g. vector quantization to produce a representative symbol. A symbol dictionary generating section 404 registers the produced representative symbol to a symbol dictionary, gives an index to the representative symbol for identifying the representative symbol to produce a symbol dictionary. A symbol position generating section 406 uses the symbol dictionary to cross-reference an index corresponding to the representative symbol with a position at which the dot pattern appears. A coding section 408 codes the generated symbol position cross-reference data with test region coding stipulated by the JBIG2 to produce the coded data. COPYRIGHT: (C)2007,JPO&INPIT