IMAGE PROCESSING APPARATUS, IMAGE PROCESSING SYSTEM, IMAGE PROCESSING METHOD, AND RECORDING MEDIUM

摘要

An image processing apparatus includes an image information acquisition unit acquiring average brightness of image data and cumulative frequency distribution of pixels related to gradation of the image data; a conversion range determination unit acquiring a conversion threshold value from the average brightness based on a previously set relationship and determining a gradation conversion range where the gradation of the image data is to be converted based on a gradation where a cumulative frequency corresponds to the conversion threshold value in the cumulative frequency distribution; and a gradation conversion unit converting the gradation of the image data in the gradation conversion range.