opencv reshape函数说明

转自http://blog.csdn.net/yang6464158/article/details/20129991

reshape有两个参数：

其中，参数：cn为新的通道数，如果cn = 0，表示通道数不会改变。

参数rows为新的行数，如果rows = 0，表示行数不会改变。

注意：新的行*列必须与原来的行*列相等。就是说，如果原来是5行3列，新的行和列可以是1行15列，3行5列，5行3列，15行1列。仅此几种，否则会报错。

具体调用也很简单，代码如下所示：

#include <iostream>
#include <opencv/cv.h>
#include <opencv/highgui.h>
int main()
{
    cv::Mat testMat = cv::Mat::zeros ( 5, 3, CV_8UC3 );
    std::cout << "size of testMat: " << testMat.rows << " x " << testMat.cols << std::endl;
    std::cout<<"testMat = "<<testMat<<std::endl;
    cv::Mat result = testMat.reshape ( 0, 3 );
    std::cout << " size of original testMat: " << testMat.rows << " x " << testMat.cols << std::endl;
    std::cout << " size of reshaped testMat: " << result.rows << " x " << result.cols << std::endl;
    std::cout << "result = " << result << std::endl;
    cv::waitKey(0);
    system("pause");
    return 0;
}

结果如下：

比如说：下面的情况就会报错：

#include <iostream>
#include <opencv/cv.h>
#include <opencv/highgui.h>
int main()
{
    cv::Mat testMat = cv::Mat::ones ( 5, 3, CV_8UC3 );
    std::cout << "size of testMat: " << testMat.rows << " x " << testMat.cols << std::endl;
    std::cout<<"testMat = "<<testMat<<std::endl;
    cv::Mat result = testMat.reshape ( 0, 6 );
    std::cout << " size of original testMat: " << testMat.rows << " x " << testMat.cols << std::endl;
    std::cout << " size of reshaped testMat: " << result.rows << " x " << result.cols << std::endl;
    std::cout << "result = " << result << std::endl;
    cv::waitKey(0);
    system("pause");
    return 0;
}

因为行和列的乘积不相等

结果如下：

我们在使用reshape的时候一定不能用定义的Mat类型赋给原来的类型，必须重新定义一个新类。

可以这样：

unsigned char v11[] = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12 };
cv::Mat A = cv::Mat(3, 4, CV_8U, v11);
cv::Mat B = A.reshape(1, 12);

但不能这样：

cv::Mat testMat = cv::Mat::zeros ( 5, 3, CV_8UC3 );
std::cout << "size of testMat: " << testMat.rows << " x " << testMat.cols << std::endl;

testMat.reshape ( 0, 1 );
std::cout << " size of reshaped testMat: " << testMat.rows << " x " << testMat.cols << std::endl;