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~(*^__^*) 

[cpp]
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/* 
*@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();  
}  

/*
*@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();
}