| 摘要 |
<P>PROBLEM TO BE SOLVED: To suppress image deterioration occurring, when gradation of image data is reduced. Ž<P>SOLUTION: An image forming apparatus includes: a resolution conversion unit 101 for converting multi-gradation image data into image data of N (N is a natural number satisfying 3≤N) tones, wherein N is less than the number of gradation of the multi-gradation image data, integrating an input pixel of interest in image data input in an input part with n (n is a natural number satisfying 2≤n) pixels that include the input pixel of interest and being contiguous in a sub-scanning direction, and determining the average value of pixel values of the n pixels as a pixel value of integrated pixels; a quantization unit 103 for quantizing the image data obtained by 101 to image data of N tones; and a pixel selection unit 104 for performing first determination processing for determining whether a difference between the pixel values of n input pixels which are contiguous in the sub-scanning direction exceeds a threshold value set, in advance, and second determination processing for determining whether a direction in which the pixel values of the n input pixels become greater is a forward direction of the sub-scanning direction or an opposite direction, and determining a pixel value of each of the n output pixels expressed with N tones. Ž<P>COPYRIGHT: (C)2010,JPO&INPIT Ž
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