| 摘要 |
PROBLEM TO BE SOLVED: To prevent production of fog in the vicinity of an edge part by converting an input image into high gradation image based on picture elements other than those of a specific attribute included in an area of a prescribed size including a conversion object picture element. SOLUTION: An attribute discrimination section 201 discriminates whether or not a picture element of interest of a received binary image as to whether or not the picture element belongs to a character/line drawing area. When the noted picture element belongs to the character/line drawing area, a selector 203 selects an output of a simple multilevel section 202 to provide an output of a multilevel image obtained by applying simple multilevel processing to the picture element of interest. When the noted picture element does not belong to the character/line drawing area, the selector 203 selects an output of an arithmetic section 206. In this case, a block size decision section 204 applies convolution to 25 picture elements in total consisting of 5 vertical picture elements × 5 horizontal picture elements around the picture element of interest and indicates a small block size to a block processing section 205 when a maximum absolute value is a threshold level or over, and indicates a large block size thereto when the maximum absolute value is less than the threshold level. An arithmetic section 206 counts number of black level picture elements in the picture element block except the character/line drawing area to calculate a high gradation image. As a result the input image is converted into a multilevel image where the edge part of the character/line drawing area is sharpened. |
