摘要：图像增强技术是图像处理领域中重要的研究课题。图像增强技术的目的是改善图像视觉效果，使处理后的图像质量更优于原图像。直方图修正技术是一种常用的方法。直方图修正技术有直方图均衡化和直方图规定化两类。
直方图均衡化是一种常用的灰度增强算法，其原理是将原图像的直方图经过变换函数修整为均匀直方图，然后按均衡化后的直方图修正原图像。直方图均衡化的基本思想是把原始图的直方图变换为均匀分布的形式，达到增加了象素灰度值动态范围的目的，从而实现增强图像整体对比度的效果。直方图均衡化处理具有良好的图像增强效果，从实现算法上可以看出，其优点主要在于能自动增强整幅图像的对比度，但具体的增强效果因此不容易控制，只能得到全局均衡化处理的直方图。
在实际应用中，往往要根据不同的要求得到特定形状的直方图分布，以有选择地对某灰度范围进行局部的对比度增强，即想要得到已知直方图的增强图像。此时，可以采用直方图规定化处理，通过选择合适的规定化函数期望的效果。直方图规定化就是针对这种思想提出来的一种直方图修正增强方法。所以，从某种意义上，直方图规定化可看做是直方图均衡化方法的改进。
本文首先介绍了数字图像处理及直方图均衡化，直方图规定化的基本原理，总结了现有的直方图规定化算法，并对其中的一种算法提出了改进措施。在分析了Visual Basic6.0和MATLAB7.0各自提供的程序接口的基础上，采用了一种通过ActiveX技术将Visual Basic和MATLAB混合编程来实现图像处理的方法。此方法突破了以往利用单一语言实现系统可靠性的限制，更广泛的利用了现有技术成果，降低了编程难度，加快了编程速度。
关键词：图像处理 直方图均衡化 直方图规定化
Abstract:Image enhancement technology is an important research topic in the field of image processing. The purpose of image enhancement technology to improve the visual effect of the processed image quality is better than the original image. Histogram modification technique is a commonly used method. Histogram correction techniques are two types of histogram equalization and histogram specification.
Histogram equalization is a common gray-scale enhancement algorithms, the original image histogram after the transformation function trimming uniform amendment to the original image histogram, and histogram equalization. The basic idea of the histogram equalization histogram transformation of the original graph for uniform distribution of the form, so to increase the dynamic range of pixel gray value and thus to enhance the overall image contrast. Histogram equalization to deal with good image enhancement can be seen from the algorithm, its main advantages lies in its ability to automatically enhance the contrast of the whole image, but the specific enhancement is not easy to control, can only be global equalizationprocessing of the histogram.
However, in practical applications, often depending on the requirements of the particular shape of the histogram distribution to selected local contrast enhancement of a gray-scale range, that is, want to get known histogram of the image enhancement.At this point, you can use the histogram provides processing by selecting the appropriate provisions of function to the desired effect. Histogram specification for this idea to a histogram correction enhancement method. So, from a sense, the histogram specification can be seen as the improvement of the histogram equalization method.
This paper first introduces the basic principles of digital image processing and histogram equalization, histogram specification, summarizes the existing histogram specification algorithm, and an algorithm proposed improvement measures. Then Visual Basic and MATLAB mixed programming. Based on the analysis of the Visual Basic6.0 and MATLAB7.0 respective program interface,using Visual Basic and MATLAB mixed programming an ActiveX technology to implement image processing. This method breaks through the previous use of a single language to achieve the limit of system reliability and maintenance of simulation, more extensive use of existing technological achievements, and reduce the difficulty of programming to speed up the programming speed.
Key Words：Image processing Histogram equalization Histogram specification
