1. An image processing apparatus for correcting a gradation of input image data, comprising: a first generating section for generating a first look up table using the input image data; a second generating section for generating a second look up table based on the first look up table and human visual characteristics; and a transforming section for transforming the image data using the second look up table, wherein the first generating section generates the first look up table based on a histogram of intensity levels of the image data.