| 摘要 |
<p>PROBLEM TO BE SOLVED: To provide a coder that quantizes a color image before color conversion at an optimum quantization rate for each component of the image so as to efficiently compress the image while suppressing the effect on the image quality. SOLUTION: An S conversion section 102 converts RGB values of a color image segmented in the unit of 4 pixels into a DC component and an AC component. An RCT(Reversible Component Transform) section 112 transforms the DC component into a luminance signal and chrominance signals. Quantization sections 103-111 quantize the AC component. In the quantization, a small quantization rate is adopted for the G component in the AC component including many luminance components and a larger quantization rate is employed for the other components R, B and an RCT section 113 transforms the quantized components into a luminance signal. Linking the components subjected to color conversion to each other generates a code of a fixed length.</p> |
