IMAGE PROCESSOR, IMAGE READING DEVICE AND IMAGE FORMING DEVICE MOUNTED WITH THE PROCESSOR, IMAGE PROCESSING METHOD, AND COMPUTER-READABLE STORAGE MEDIUM STORED WITH IMAGE PROCESSING PROCEDURE

摘要

PROBLEM TO BE SOLVED: To securely detect an edge in a color image by detecting the edge on the basis of the saturation data calculated from image data of the respective R, G, and B colors. SOLUTION: At an edge detection part 182, image data of the respective R, G, and B colors are inputted to a luminosity calculation part 191 and a saturation calculation part 192. The lightness calculation part 191 calculates lightness data and the saturation calculation part 192 calculates saturation data. The calculates lightness data and saturation data are inputted to differential filters 193 and 194 and the respective gradients are calculated. Their outputs are inputted to a comparison part 195, which compares their absolute values with a determined threshold. When the absolute values of the output values are larger than the threshold, a signal '1' showing that a pixel of interest is an edge is outputted, but when less than the threshold, a signal '0' showing that the pixel of interest is not an edge is outputted. When the signal output is supplied to an OR circuit 196 and an edge is detected with at least one of the absolute values, it is detected that a regard pixel is the edge.