| 摘要 |
<P>PROBLEM TO BE SOLVED: To reduce a risk of incorrect detection of a foreign substance attached to the reading position of a line sensor. <P>SOLUTION: In an image data for one color component, when a density value variation between a target pixel and a pixel adjacent to the target pixel exceeds a first reference value, the target pixel is defined to be a top pixel, each density value is successively compared between the top pixel and each pixel succeeding the top pixel. Also, a first pixel having a density value equal to or greater than the density value of the top pixel is defined to be an end pixel. When the number of pixels in a pixel group (tentative foreign substance region) from the top pixel continuing to the end pixel is smaller than a second reference value, and an average density value among the entire pixels in the tentative foreign substance region is a third reference value or greater, if in an image data for other one color component, a difference between the pixel density value associated with the top pixel and the average pixel density value associated with the entire pixels in the tentative foreign substance region is smaller than a fourth reference value, it is determined that a foreign substance exists at the reading position of the line sensor corresponding to the one color component. <P>COPYRIGHT: (C)2013,JPO&INPIT |
