1. A color image compression method for compressing color images read by an optical sensor, comprising: dividing a color image into a plurality of areas and determining a characteristic of each area, based on both a distributed amount of a color value and a distributed amount of a hue value of a pixel in each area, upon calculating the distributed amount of the color value and the distributed amount of the hue value of each area of a color image, if the distributed amount of the color value exceeds a first reference value and the distributed amount of the hue value exceeds a second reference value, it is determined that the area is a photograph area; if the distributed amount of the color value exceeds the first reference value and the distributed amount of the hue value is below the second reference value, it is determined that the area is a ruled line area or a character area; and if the distributed amount of the color value is below the first reference value, it is determined that the area is a background/plane area; counting the number of appearances of the hue value of each pixel of a color image, generating a hue histogram of pixels in other than a photograph area and storing the hue histogram in a storage unit; reducing the number of hue values of the entire color image to obtain a number-reduced hue value, based on the hue histogram, allocating the number-reduced hue value to each pixel and classifying the pixels of the entire color image into clusters, based on the newly allocated hue value; and determining a characteristic of each of the clusters and encoding pixels in each cluster of the clusters by a coding method suitable for the characteristic of each of the clusters.