opencv 彩色图像对比度增强

一般地，图像对比度都是在灰度图上进行增强，这在我的一篇文章中已经给出了实现方法（http://blog.csdn.net/abcjennifer/article/details/7401921），最通常的办法就是直方图均衡化，而彩色图像的对比度增强其实道理相同。这里给出我的实现方法：

首先将RGB图像转到YCbCr分量，然后对Y分量上的图像进行直方图均衡化，最后进行图像合成。详见代码~(*^__^*) 

/*
*@Function: Color image contrast enhancement
*@Date: 2012-4-5
*@Author: 张睿卿
*/

int ImageStretchByHistogram(IplImage *src1,IplImage *dst1)
/*************************************************
Function:      通过直方图变换进行图像增强，将图像灰度的域值拉伸到0-255
src1:               单通道灰度图像                  
dst1:              同样大小的单通道灰度图像 
*************************************************/
{
	assert(src1->width==dst1->width);
	double p[256],p1[256],num[256];

	memset(p,0,sizeof(p));
	memset(p1,0,sizeof(p1));
	memset(num,0,sizeof(num));
	int height=src1->height;
	int width=src1->width;
	long wMulh = height * width;

	//statistics
	for(int x=0;x<src1->width;x++)
	{
		for(int y=0;y<src1-> height;y++){
			uchar v=((uchar*)(src1->imageData + src1->widthStep*y))[x];
			num[v]++;
		}
	}
	//calculate probability
	for(int i=0;i<256;i++)
	{
		p[i]=num[i]/wMulh;
	}

	//p1[i]=sum(p[j]);	j<=i;
	for(int i=0;i<256;i++)
	{
		for(int k=0;k<=i;k++)
			p1[i]+=p[k];
	}

	// histogram transformation
	for(int x=0;x<src1->width;x++)
	{
		for(int y=0;y<src1-> height;y++){
			uchar v=((uchar*)(src1->imageData + src1->widthStep*y))[x];
			((uchar*)(dst1->imageData + dst1->widthStep*y))[x]= p1[v]*255+0.5;            
		}
	}
	return 0;
}

void CCVMFCView::OnYcbcrY()
{
	IplImage* Y = cvCreateImage(cvGetSize(workImg),IPL_DEPTH_8U,1);
	IplImage* Cb= cvCreateImage(cvGetSize(workImg),IPL_DEPTH_8U,1);
	IplImage* Cr = cvCreateImage(cvGetSize(workImg),IPL_DEPTH_8U,1);
	IplImage* Compile_YCbCr= cvCreateImage(cvGetSize(workImg),IPL_DEPTH_8U,3);
	IplImage* dst1=cvCreateImage(cvGetSize(workImg),IPL_DEPTH_8U,3);

	int i;
	cvCvtColor(workImg,dst1,CV_BGR2YCrCb);
	cvSplit(dst1,Y,Cb,Cr,0);

 	ImageStretchByHistogram(Y,dst1);
 
 	for(int x=0;x<workImg->height;x++)
 	{
 		for(int y=0;y<workImg->width;y++)
 		{
 			CvMat* cur=cvCreateMat(3,1,CV_32F);
 			cvmSet(cur,0,0,((uchar*)(dst1->imageData+x*dst1->widthStep))[y]);
 			cvmSet(cur,1,0,((uchar*)(Cb->imageData+x*Cb->widthStep))[y]);
 			cvmSet(cur,2,0,((uchar*)(Cr->imageData+x*Cr->widthStep))[y]);
 
 			for(i=0;i<3;i++)
 			{
 				double xx=cvmGet(cur,i,0);
 				((uchar*)Compile_YCbCr->imageData+x*Compile_YCbCr->widthStep)[y*3+i]=xx;
 			}
 		}
 	}
 
	cvCvtColor(Compile_YCbCr,workImg,CV_YCrCb2BGR);
 	m_ImageType=3;
 	Invalidate();
}