Patent ID: 7791759

Claim:
An image processing method performed by an image processing apparatus that includes a controller, the method comprising the steps of: detecting a dynamic range of input image data; performing edge enhancement processing that amplifies high-frequency components of the input image data, where a bit number of grayscale levels of the input image data is increased; performing dithering processing using one of a plurality of dither matrices respectively having different pseudo-grayscale levels, to reduce the bit number of grayscale levels of each pixel of the image data that has been processed by the edge enhancement processing; and determining the one of the plurality of dither matrices to be used in the dithering processing based on a combination of a parameter indicating a dynamic range of the input image data and a parameter indicating an enhancement coefficient of the edge enhancement processing, wherein the determining is performed, at least in part, by the controller, and wherein the pseudo-grayscale levels of the dither matrix used in the dithering processing is increased when the enhancement coefficient of the edge enhancement processing is relatively low or when the dynamic range of the input image data is relatively narrow, wherein the plurality of dither matrices includes at least four dither matrices respectively having pseudo-grayscale levels A, B, C, and D (A>B>C>D), wherein the dither matrix having pseudo-grayscale level A is determined to be used, in the determining step, when the enhancement coefficient of the edge enhancement processing is relatively low and the dynamic range of the input image data is relatively narrow, wherein the dither matrix having pseudo-grayscale level B is determined to be used, in the determining step, when the enhancement coefficient of the edge enhancement processing is relatively low and the dynamic range of the input image data is relatively wide, wherein the dither matrix having pseudo-grayscale level C is determined to be used, in the determining step, when the enhancement coefficient of the edge enhancement processing is relatively high and the dynamic range of the input image data is relatively narrow, and wherein the dither matrix having pseudo-grayscale level D is determined to be used, in the determining step, when the enhancement coefficient of the edge enhancement processing is relatively high and the dynamic range of the input image data is relatively wide.