| 摘要 |
According to this invention, in image data A and B which are respectively constituted by pixel groups SIGMA Aij and SIGMA Bij consisting of N pixels Aij and Bij (N is a positive integer; i and j respectively indicate a row position and a column position), and in which density data Adij and Bdij of the pixels are expressed by n(2m)-bit data (n and m are positive integers), designated 2m-bit portion aij of each density data Adij of image data A is divided into upper m-bit portion aUij and lower m-bit portion aLij. A histogram processor (16) calculates SIGMA aij.bij between 2m-bit portions aij and bij using a histogram obtained by the upper or lower m-bit portion aUij or aLij and designated 2m-bit portion bij of each density data Bdij of pixel group SIGMA Bij. An average can also be calculated by a calculation section (32) using the histogram. Therefore, a covariance can be calculated at high speed. |
