| 摘要 |
This invention has as its object to efficiently compress a mixed image which includes both natural and non-natural images upon encoding and decoding image data. To achieve this object, in an image encoding apparatus according to this invention, a line buffer (101) segments image data (131) input from an image scanner (130) for inputting image data into a plurality of regions, a discrimination unit (120) discriminates the ratio of regions each having a predetermined nature to the image data (131), a quantization matrix selector (121) selects a quantization matrix used to compress the region on the basis of this ratio, an image data encoder (103) compresses the region using the selected quantization matrix, and an attribute flag encoder (102) compresses information which helps the decoding side estimate a quantization matrix used to encode the region.
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