| US 7,570,824 B2 | ||
| Image processing method, image processor, image forming apparatus and memory product | ||
| Terumitsu Katougi, Chiba (Japan); Shiro Wakahara, Chiba (Japan); and Kazuyuki Hamada, Nara (Japan) | ||
| Assigned to Sharp Kabushiki Kaisha, Osaka (Japan) | ||
| Filed on Jul. 08, 2004, as Appl. No. 10/886,729. | ||
| Claims priority of application No. 2003-273501 (JP), filed on Jul. 11, 2003; application No. 2003-334272 (JP), filed on Sep. 25, 2003; and application No. 2003-365097 (JP), filed on Oct. 24, 2003. | ||
| Prior Publication US 2005/0008245 A1, Jan. 13, 2005 | ||
| Int. Cl. G06K 9/36 (2006.01) | ||
| U.S. Cl. 382—239 [382/162; 382/232] | 37 Claims |
| 1. An image processing method comprising the steps of:
receiving image data; and
using a processor to perform the following steps of:
transforming image data into spatial frequency components;
quantizing the transformed spatial frequency components;
performing a modification process of changing spatial frequency components in a predetermined frequency domain on the quantized
spatial frequency components;
inverse-quantizing the spatial frequency components on which the modification process is performed;
inverse-transforming the inverse-quantized spatial frequency components into image data; and
reducing a number of gray levels in the inverse-transformed image data, based on a threshold value.
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