1. An image processing circuit arranged to perform brightness conversion processing according to a brightness conversion coefficient on each pixel of an input image and produce an output image, the image processing circuit comprising a division section to divide a region of the input image into a plurality of areas; and a histogram calculation section to calculate a histogram for each area, and a first calculation section to calculate an area-by-area conversion coefficient for each area based on the result from the histogram calculation section, wherein the image processing circuit is arranged to determine the brightness conversion coefficient based on a result from the histogram calculation section and based on the area-by-area conversion coefficient, the image processing circuit further comprising a filter section arranged to low-pass filter the area-by-area conversion coefficient in terms of images and locations, wherein the filter section is arranged such that when the filtering is performed on an area of interest, the area-by-area conversion coefficient of an area included in a predetermined range around the area of interest is used, and when at least part of the predetermined range is located outside the region of the image, a predetermined imaginary coefficient is assigned to the part and the filtering is performed by regarding the imaginary coefficient as the area-by-area conversion coefficient.