| 摘要 |
PURPOSE:To detect at a high speed whether a density unevenness exists or not, and also to detect it exactly irrespective of whether the whole image is dark or light, by converting a difference of a density distribution of an image to a cumulative value from a composite histogram, and normalizing it by a density width. CONSTITUTION:A cumulative density histogram calculating circuit 10 executes an accumulation by each level exceeding a discriminating level, with respect to a density histogram of a partial area in which the number of picture elements for constituting a pattern exceeds a prescribed number, outputs it to a normalized cumulative density histogram calculating circuit 11, and by dividing it by the maximum level, a normalized cumulative density histogram is calculated. Subsequently, in an unevenness coefficient calculating circuit 12, the normalized cumulative density histogram is synthesized, an are surrounded by the maximum envelope and also the maximum level is extracted. Next, a level width between the maximum level and the discriminating level is calculated, the area surrounded by the maximum envelope and the minimum envelope is normalized by the level width, and the obtained value is set as an unevenness coefficient and sent out to a density unevenness deciding circuit 13.
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