| 摘要 |
PURPOSE:To remove unrequired data such as background or reversed printed characters by setting a threshold value corresponding to the deviation of image density. CONSTITUTION:A CCD part 3a performs the A/D conversion of an analog electric signal inputted from a CCD corresponding to each value of pixel density, performs MTF correction, white-and-black correction of gamma correction and outputs an 8-bit digital signal to a means value processing part 3b. Then, a density means value A of a low density gradation area, mean value C of high density area and mean value B of entire density are calculated. The mean value A shows the stain density of a picture and the means value C shows line drawing density. When a half tone such as a photograph or a picture is contained, however, the image is expressed by the entire gradation, and the values A, B and C are concentrated near the intermediate gradation. Therefore, it can be discriminated whether or not the original is written in line drawing, further, the threshold value is calculated corresponding to the result, a part smaller than this value is removed, and stain caused by the peak of deep background or reversed print, etc., can be removed. |
