C++(OpenCV) 计算图像局部方差

图像局部方差计算公式：

其中，I(x+i, y+j)表示以(x, y)为中心的坐标点的像素；Ws表示窗口内像素的个数；M(x)表示局部窗口内的均值

具体实现代码：

float* getLocalVar(Mat& img, int r,  float* localVarImg)
{
   // 输入参数：img, r
   // 输出参数：localVarImg
   // 输入参数r表示窗口半径
   // 对图像进行边界填充
	Mat borderImg(Size(img.cols + 2*r, img.rows + 2*r), CV_8UC1, -1);
	cv::copyMakeBorder(img, borderImg, r, r, r, r,BORDER_DEFAULT);

	for(int i = r; i < img.rows + r; i++)
	{
		for(int j = r; j < img.cols + r; j++)
		{
			 double localSum = 0;
			 float  localAve = 0;
			 float  localVar = 0;

			 //局部窗口内像素求和localSum
		     for( int m = i-r; m <= i+r; m++)
			 {
				 for(int n = j-r; n <= j+r; n++)
				 {
				  //	 cout<<"read value: "<<(int)borderImg.at<uchar>(m, n)<<endl;
					 localSum = localSum + borderImg.at<uchar>(m, n);
				  //	 cout<<"localSum: "<<localSum<<endl;
				 }
			 }

			 // 局部窗口内像素的均值计算localAve;
			 localAve = localSum / POW(2*r+1);
			 localSum = 0;

			 // 局部窗口内每个像素与均值差求和
			 for(int m = i-r; m <= i+r; m++)
			 {
				 for(int n = j-r; n <= j+r; n++)
				 {
					// cout<<borderImg.at<uchar>(m, n) - localAve<<endl;
					 localSum = localSum + POW(borderImg.at<uchar>(m, n) - localAve);
				 }
			 }

			 // 局部方差
			 localVar = localSum*1.0 / (POW(2*r+1));
			 localVarImg[(i-r)*img.cols + (j-r)] = localVar;
		}
	}
	return localVarImg;
}

函数调用实例：

int main(int argc, char* argv)
{

	// 图像索引编号
	int imgIndex = 9;
	string imageIndex;
	
	//int类型 转 string类型
	stringstream ss;
	ss<<imgIndex;
	ss>>imageIndex;

	string path   = "..//data//";
	string IRFile = "IR_";
	string imgFormat = ".bmp";
	string IRImgFile = path + IRFile + imageIndex + imgFormat;

	Mat IRImg = imread(IRImgFile, 0);
	if(IRImg.empty())
	{

		 CV_Error(CV_StsBadArg, "read image wrong, pease check ");
	}
	if(IRImg.channels() == 3)
	{
		cv::cvtColor(IRImg, IRImg, CV_RGB2GRAY);
	}
	imshow("IRImg", IRImg);

	float* IRWeight  = 0;
	int r = 3;
	IRWeight  = new float[IRImg.cols * IRImg.rows];
	getLocalVar(IRImg, r, IRWeight);
 
    return 0；

}