1. An image processing apparatus comprising: a block histogram generation unit configured to calculate frequency of a pixel value in each block including plural pixels, divide a dynamic range into plural “N” numbers (N is an integer), and generate a first histogram including “N” number of bins having a width of plural pixels; a pixel histogram generation unit configured to calculate frequency of a target pixel depending on a pixel position of the target pixel in a block based on the first histogram of the block including the target pixel and the first histogram of a block adjacent to the block including the target pixel, and generate a second histogram including “N” number of bins for each pixel; and an output value determination unit configured to generate a relation between the pixel value and an output value of the pixel value based on the second histogram so that a maximum cumulative frequency of the second histogram matches a maximum value of the output value of the pixel value, and calculate the output value based on the pixel value of the target pixel.