| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide an image compression apparatus capable of performing BTC compression of a color image with proper image reproducibility. <P>SOLUTION: A color image is divided into blocks of 4×4 pixels, or the like, and BTC compression is performed on each block for each color component, wherein a value in normalizing the gradation value of each color component is adjusted, in such a way that the color of an original pixel and a color of a compressed/expanded pixel become the closest. Namely, when the gradation value to be normalized is in the vicinity of threshold, regions on both sides of the threshold are set as candidates at normalization, and under a condition where a color at reproduction becomes closer, any one of regions is selected from among the candidates. <P>COPYRIGHT: (C)2009,JPO&INPIT |
