Patent ID: 7359568

Claim:
An image processing apparatus, comprising: an input section inputting information of an image; a converter converting the information of the image inputted by said input section into information suitable for edge detection; and an image processor calculating a difference value of each image unit between adjacent image units mutually in a predetermined direction to generate an edge image based on the converted information of the image, wherein the image processor adds an absolute value of the difference value of the image unit to a difference value of adjacent image unit to the image unit in the predetermined direction when the difference value of the image unit calculated by the image processor is negative, wherein the input section inputs information of an image in which an area of noninverted characters and an area of inverted characters are mixed, and wherein the image processor generates an edge image for the noninverted characters and an edge image for the inverted characters, selects either of the generated edge images for each character string area, and composes the selected edge images for each character string area to form one edge image.