| 摘要 |
PROBLEM TO BE SOLVED: To binarize gray level image data at a high speed by a desired threshold by storing image data provided with the same gradation value as one group in the state of being divided for a plurality of groups. SOLUTION: A gray level image memory comprises a list memory 221 and a pointer memory 222. In a state where an address (j×I+i) is allocated to a cell (i, j) corresponding to a pixel (i, j) in the list memory 221 and the 2<m> kinds of the addresses corresponding to the gradation values at the pointer memory 222 are turned to the leading address of a gradation value correspondence list, gray level image data are stored corresponding to the 2<m> kinds of the gradation values in the list memory 221 as the address on the gradation value correspondence list. When reading out, the address on the gradation value correspondence list is turned to the leading address, the address on the gradation value correspondence list is successively traced on the list memory 221 and the respective addresses are successively transformed to the coordinate of the picture element (i, j) and read. |
