| 摘要 |
PROBLEM TO BE SOLVED: To obtain a high S/N in the image compression coding employing predictive coding. SOLUTION: Digital image data are fed to a differential pulse coding modulation DPCM circuit 10, where a difference from an adjacent pixel is calculated. Not a difference from a just preceding pixel but a difference from a mean value of a just preceding pixel and pixels included in one-preceding line is calculated. The calculated difference is fed to an adaptive DPCM(ADPCM) circuit 12 and a quantization width is increased/decreased by using a prescribed threshold to quantize the difference. The quantized difference is fed to a Huffman coding circuit 14, where the difference is compression-coded and outputted. Since the difference is calculated by using pixel data of one-preceding line of a line including processing object pixel, predictive coding taking 2-dimension correlation of an image into account is attained and a high S/N is obtained. |
