| 摘要 |
<p><P>PROBLEM TO BE SOLVED: To provide an image data compression method capable of attaining reversible compression of image data of an index form and irreversible / high efficiency compression of image data in an RGB form or a YUV form and a decompression apparatus of compressed data. <P>SOLUTION: First, image data are divided into a plurality of blocks, image data of each block are scanned in a predetermined order and rearranged. Wavelet transformation is applied to the data obtained by rearrangement and quantization and threshold value control are applied to the data after the wavelet transformation. Then a difference arithmetic operation and encoding are performed, and in the case of irreversible compression, the wavelet transformation, the quantization and the threshold control are not performed. The processes above are repetitively executed by changing the scan method, a scan method providing the smallest data quantity after the compression is selected, the selected scan method and the compressed image data on the basis of the scan method are outputted. The decompression apparatus reversely executes the compression processes to restore the compressed data to the original data. <P>COPYRIGHT: (C)2004,JPO</p> |
