| 摘要 |
PROBLEM TO BE SOLVED: To provide a context generation method, an image compression method and an image processor for generating reference state (or context) to improve the compression rate, without increasing the number of the context (the number of reference tables) so much. SOLUTION: As a bit arrangement of address data for deciding a context at calculation encoding processing in image compression, besides a surrounding image element value m bit of pixel of attention, values Q1,..., Qn other than a pixel value of this surrounding pixel are operated, and the operation result P1+...+Pn is added to the bit arrangement of the address data for context decision. In the operation, as a result of binarization by an average value of the pixel value of an input pixel, an average density and the result of binarization by a corresponding dither threshold, quality and attribute information of an image, including an edge part and a flat part of the image, a change rate of the average density in an area of plural pixels, the size and positive or negative signs and so on are calculated, and binary or a multi-valued output is set as the operation results. |
