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（/article/1820987.html），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~(*^__^*)

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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();

}