Abstract: Modified histogram to make the image as a whole or a part of the gray-scale transformation of gray, is an important aspect of image enhancement. Mature modified histogram, histogram Equalization and the provisions of the law.This histogram extension method,which features both balanced and provisions of the law. This law defines the concept of transformation than departure raises rates,high and low-side transformation from original image histogram adjusted than determine new histogram of an image, resulting in a new image in order to achieve the purpose of gray-scale transformation on the original image. Applies the law of CT image processing have obtained satisfactory results.

Key words: Histogram, Extension method, Transformation ratio, Expansion rate