| 摘要 |
<P>PROBLEM TO BE SOLVED: To perform coding with higher compression efficiency, while maintaining resolution about an image, such as, characters and line drawings having high-frequency components, and suppressing image deterioration regarding a gradation image such as a natural image. <P>SOLUTION: An extraction part 102 determines colors of pixels of the high frequency components in input image data as extracted colors, and generates identification information for indicating which of the extracted colors/non-extracted colors the pixels in the image data are for each pixel in the image data. A replacement part 104 replaces pixel values of the extracted colors with an average value of the non-extracted colors. A reduction part 105 reduces the inside of the image data, after the replacement to one half, both horizontally and vertically by generating a single pixel, from 2×2 pixels by using a window of 2×2 pixel size. At this time, when at least one non-extracted pixel exists in the window, an average value of the non-extracted colors in the window is determined as a pixel value of the reduced image. Then, a packing part 107 couples the extracted colors, reversible coding results of the identification information, and irreversible coding data about the reduced image to one another to be output as coded data of the input image data. <P>COPYRIGHT: (C)2009,JPO&INPIT |
