| 摘要 |
<p>PROBLEM TO BE SOLVED: To obtain high image quality in spite of a small number of colors by generating a limited color image whose number of colors in use is limited from an original image, converting the limited color image into an image of a pallet color form consisting of a color pallet and a color number, generating a limited color image of a plurality of layers with different number of colors in use and encoding the image of a medium layer. SOLUTION: Original image data consist of R, G, B data with 256-gradation each in 24-bits per pixel. The subtractive color processing such as the median cut method is employed to limit number of colors in use into, e.g. 256 colors and color numbers of 0-255 are given to the 256 colors to obtain image data of a pallet color form in 8-bits per pixel. N-layers of limited color images whose number of colors in use differs from each other are generated, the original image is selected as the (N+1)-th layer, and the k-th layer image (2<=k<=N+1) is encoded with no distortion while decreasing the redundancy among the layers. The image data are efficiently compressed by utilizing the similarity of colors of color pallets of the adjacent layers.</p> |
