| 摘要 |
PURPOSE: To form a high-definition image by deciding a threshold value based on the density value of an extracted formed material picture element and further thresholding the density value based on the threshold value to form an edge suitable for a degraded image. CONSTITUTION: Image data stored in frame memories 103R, 103G and 103B are read into a RAM 107 for each line. Among the data read into the RAM 107, the data for which density difference between adjacent two picture elements is larger thanαare detected as inclination presence. When the picture elements provided with this inclination are continued more thanβin the same direction, those picture elements are extracted. A threshold value Th1 is calculated from the density value of these extracted picture elements, and the density value is replaced with the threshold value Th1. In this case, the average value of maximum and minimum density value stored in the RAM 107 is defined as the threshold value Th1. When the picture element provided with the density higher than this threshold value Th1 is converted to the maximum density value and the picture element provided with density lower than the threshold value Th1 is converted to the minimum density value, the image can be threshold processed.
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