Patent ID: 7990579

Claim:
An image processing apparatus comprising: an acceptance section that accepts image information; an edge detection section that subjects the image information accepted by the acceptance section to edge detection; and a screen processing section that subjects the image information to screen processing, which utilizes area coverage modulation, in accordance with a result of detection performed by the edge detection section, wherein the edge detection section comprises: a first edge determination section that determines a pixel of interest by whether the pixel of interest belongs to an edge portion or a non-edge portion by reference to information about a density of the pixel of interest and information about densities of pixels around the pixel of interest determined by an edge detection window; and a second edge determination section that compares minimum density information among the information about densities of pixels around the pixel of interest determined by the edge detection window only with a predetermined background threshold value, and that redetermines whether the pixel of interest determined by the first edge determination section belongs to the edge portion or the non-edge portion, wherein, when the first edge determination section determines the pixel of interest belongs to the edge portion in cases where the minimum density is equal to or greater than the predetermined background threshold value, the second edge determination section overturns a determination of the first edge determination and determines the pixel of interest as belonging to the non-edge portion, the screen processing section has a plurality of different screen processing modes specifying a plurality of different numbers of screen lines, the second edge determination section has a plurality of background threshold values, the plurality of background threshold values are set in advance to correspond to the plurality of different numbers of screen lines, and the second edge determination section switches the background threshold value according to a number of screen lines.