1. An apparatus for analyzing a histogram of an image, the apparatus comprising: an image input module for buffering an input image; a block calculator for performing a blocking operation for dividing the image, which has been input to the image input module, into pixel blocks of a predetermined size, and extracting and outputting a representative pixel of each block obtained by corresponding blocking; a probability density function (PDF) operator for calculating a first histogram by using all pixels of the image, which has been input to the image input module, and calculating a second histogram by using the representative pixels input from the block calculator; and an image characteristic comparator for receiving the first and second histograms output from the PDF operator, testing if the received histograms satisfy a predetermined identity criterion by comparing characteristics of the first histogram with characteristics of the second histogram, and calculating a third histogram of the input image in a scheme for the blocking when it has been determined as a result of the test that the predetermined identity criterion is satisfied.