Method and apparatus for encoding image data, and computer-readable recording medium in which program for encoding image data is recorded

摘要

An accurate encoding of image data representing a source image, which data is divided into a multiplicity of blocks is performed in accordance with features of the source image by defining a plurality of sub-areas each of which including one or more blocks; quantizing the multiple blocks; counting the number of valid coefficients among the quantization coefficients in each sub-area; adjusting the quantization coefficients of the plural sub-area in accordance with a distribution of the number of valid coefficients over the plural sub-areas (that is, a degree of appearance of the valid coefficients of each sub-area); and encoding the adjusted quantization coefficients. In addition to the accuracy, encoding of image data using sub-areas enhances a speed of processes.