opencv mat

mat基础教程：

http://blog.csdn.net/sinat_31802439/article/details/50083291

mat 初始化：

Mat M(0,3,CV_32FC1);
Mat shftMat=(Mat_<double>(3,3)<<1.0,0,leftImg.cols, 0,1.0,0, 0,0,1.0);

mat 读取：

topleft2 = presentToLastCorners.col(0);
topleft2<float>(0,0);

Keep in mind that the size identifier used in the at operator cannot be chosen at random. It depends
on the image from which you are trying to retrieve the data. The table below gives a better insight in this:
- If matrix is of type `CV_8U` then use `Mat.at<uchar>(y,x)`.
- If matrix is of type `CV_8S` then use `Mat.at<schar>(y,x)`.
- If matrix is of type `CV_16U` then use `Mat.at<ushort>(y,x)`.
- If matrix is of type `CV_16S` then use `Mat.at<short>(y,x)`.
- If matrix is of type `CV_32S` then use `Mat.at<int>(y,x)`.
- If matrix is of type `CV_32F` then use `Mat.at<float>(y,x)`.
- If matrix is of type `CV_64F` then use `Mat.at<double>(y,x)`.

在Mat.at中看到

mat 转变数据类型： 转载自http://blog.csdn.net/xiaxiazls/article/details/51204265

cv::Mat matTemp = cv::Mat::zeros(100,100,CV_32F); //得到一个浮点型的100*100的矩阵  
cv::Mat MatTemp2;  
matTemp.convertTo(MatTemp2, CV_8U); //把矩阵matTemp转为unsing char类型的矩阵，注在转换过程中有可能数值上会出现一些变化，这个要注意  

如何初始化一个任意大小mat

使用构造函数

Mat formedMat(1380,480,CV_8UC3);

图片彩色转黑白

http://blog.csdn.net/qq5132834/article/details/37736693

cvtColor(OpencvimageColor,OpencvimageGray,COLOR_RGB2GRAY);

将两幅图像链接成一幅图片

http://blog.csdn.net/quincuntial/article/details/49947791

计算图片像素平均值和方差

void meanStdDev_test()
{
    const char* imagename = "E:/1.jpg";   
    //产生灰度图
    Mat img = imread(imagename);
    Mat gray,color;
    cvtColor(img, gray, CV_RGB2GRAY);
    cout << "Channel: " << gray.channels() << endl;

    Mat tmp_m, tmp_sd;
    double m = 0, sd = 0;

    m = mean(gray)[0];
    cout << "Mean: " << m << endl;

    meanStdDev(gray, tmp_m, tmp_sd);
    m = tmp_m.at<double>(0,0);
    sd = tmp_sd.at<double>(0,0);
    cout << "Mean: " << m << " , StdDev: " << sd << endl;
}

Mat type()返回值对应类型：

http://ninghang.blogspot.com/2012/11/list-of-mat-type-in-opencv.html

使用mat出现corrupted unsorted chunks corrupted double-linked list错误，原因在于原来按Mat(col,row) 访问mat，应该是按照Mat(row,col)访问mat才对

逐点访问Mat

http://blog.csdn.net/xiaowei_cqu/article/details/7771760

Mat& ScanImageAndReduceIterator(Mat& I, const uchar* const table)
{
    // accept only char type matrices
    CV_Assert(I.depth() != sizeof(uchar));
    const int channels = I.channels();
    switch(channels)
    {
    case 1:
        {
            MatIterator_<uchar> it, end;
            for( it = I.begin<uchar>(), end = I.end<uchar>(); it != end; ++it)
                *it = table[*it];
            break;
        }
    case 3:
        {
            MatIterator_<Vec3b> it, end;
            for( it = I.begin<Vec3b>(), end = I.end<Vec3b>(); it != end; ++it)
            {
                (*it)[0] = table[(*it)[0]];
                (*it)[1] = table[(*it)[1]];
                (*it)[2] = table[(*it)[2]];
            }
        }
    }
    return I;
}