Automatic tone correction apparatus, automatic tone correction method, and automatic tone correction program storage mediums

摘要

An automatic tone correction apparatus comprises a luminance distribution formation circuit for forming a luminance histogram of an input image; a center-of-gravity calculation circuit for calculating the center of gravity of a low-luminance part of the luminance histogram; a distribution range calculation circuit for calculating a maximum value and a minimum value on an input luminance level axis; a target value storage circuit for holding a luminance correction target value; a correction table formation circuit for forming a correction table for expanding the luminance distribution and, simultaneously, correcting the luminance histogram so that the center of gravity matches the luminance correction target value; and an image signal correction circuit for performing tone correction on the basis of the correction table. Therefore, whether the input image is a forward-light image or a back-lighted image, the apparatus performs tone correction using the same processing.