opencv 笔记

OpenCV 中 minMaxLoc 用法

函数原型:
void minMaxLoc( const Mat& src, double* minVal, double* maxVal=0, Point* minLoc=0, Point* maxLoc=0, const Mat& mask=Mat() );
void minMaxLoc(const MatND& src, double* minVal, double* maxVal, int* minIdx=0, int* maxIdx=0, const MatND& mask=MatND() );
void minMaxLoc(const SparseMat& src, double* minVal, double* maxVal, int* minIdx=0, int* maxIdx=0);

说明:
1 minMaxLoc寻找矩阵(一维数组当作向量,用Mat定义) 中最小值和最大值的位置.
2 参数若不需要,则置为NULL或者0,即可.
3 minMaxLoc针对Mat和MatND的重载中 ,第5个参数是可选的(optional),不使用不传递即可.

代码:

Mat tmpCount(8, 1, CV_32FC1); 
float tmpCountMinVal = 0, tmpCountMaxVal = 0; 
Point minPoint, maxPoint; 
minMaxLoc(tmpCount, &tmpCountMinVal, &tmpCountMaxVal, &minPoint, &maxPoint); 
minMaxLoc(temp1, &minVal, NULL, &minCoor,NULL); // 不需要的数据,参数置为NULL 
cout<<minVal<<endl; 
minMaxLoc(temp1, 0, &maxVal, 0,& maxCoor); // 不需要的置为0 
cout<<maxVal<<endl;

结果:
10.9525 13.4054 17.6646 10.5643 1.22926 5.95938 11.14 4.83435
1.22926 17.6646
1.22926
17.6646

---------------------------------计时函数------------------------------------------

double t = (double)getTickCount();

t = ((double)getTickCount() - t)/getTickFrequency();
cout << "Times passed in seconds: " << t << endl;

///调用了API函数 通过得到计算机的计时频率计算相应的时间

/// getTickFrequency()为计算机的计时频率

------------------------------------------------------------------------

------------------------------------缩放Resize---------------------

double scale=0.5; //设置缩放倍数
string imageurl = "F:/opencv/samples/cpp/baboon.jpg";
Mat image =imread(imageurl);A
//缩放 
Size dsize = Size(image.cols*scale,image.rows*scale);
Mat image2 = Mat(dsize,CV_32S);
resize(image, image2,dsize);

----------------------------------------------------------------

--------------选取矩阵中复合要求的元素--------------------

   Mat test=(Mat_<unsigned char>(10,1)<<1,2,3,4,5,6,7,8,9,10);
	Mat b=(Mat_<unsigned char>(10,1)<<1,2,3,4,5,6,7,8,9,10);
	test=test>5;
	test=test/255;
	cout<<test<<endl;
	cout<<b<<endl;
	int t1=test.type();//类型t1,t2必须相同
	int t2=b.type();
	Mat c(test.mul(b));
	cout<<c<<endl;

---------------------------------------------------------------------------

Mat 类型转换

 Mat a = Mat_<unsigned short> (10, 3);//或Mat a = Mat_<unsigned char> (10, 3)

   Mat_<float> b;

   a.ConvertTo(b, CV_32F);

cout<<"a type"<<endl<<a.depth()<<endl<<"b type"<<endl<<b.depth()<<endl;