opencv Mat 函数--CheckVector

偏执的太偏执、 2022-08-31 05:59 194阅读 0赞

学习opencv ，我们需要对opencv的函数有点了解 ，实现什么样子的功能，以及如何实现

下面我们一次来看checkVector 这个函数，

int org.opencv.core.Mat.checkVector(int elemChannels)

elemChannels  的取值

# 单通道 #

单通道：取值== 矩阵的列数

返回结果：矩阵的行数

我们来验证一个这个理解是否正确

Mat truth = new Mat(4, 10, CvType.CV_8UC1) {
    			{
    				put(0, 0, 01, 02, 03, 04, 05, 06, 07, 8, 9, 0, 01, 02, 03, 04, 05, 06, 07, 8, 9, 0);
    				put(1, 0, 11, 12, 13, 14, 15, 16, 17, 18, 19, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 10);
    				put(2, 0, 21, 22, 23, 24, 25, 26, 27, 28, 29, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 20);
    				put(3, 0, 31, 32, 33, 34, 35, 36, 37, 38, 39, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 30);
    
    			}
    		};
        	System.out.println(truth.checkVector(10));

![\\begin\{bmatrix\} 1 & 2 & 3 & 4 & 5 & 6 & 7 & 8 & 9 & 0 \\\\ 11 & 12 & 13 & 14 & 15& 16 & 17 & 18 & 19 & 10 \\\\ 11 & 12 & 13 & 14 & 15& 16 & 17 & 18 & 19 & 10 \\\\31 & 32 & 33 &34 &35 &36 & 37 & 38 & 39 & 30 \\end\{bmatrix\}][begin_bmatrix_ 1 _ 2 _ 3 _ 4 _ 5 _ 6 _ 7 _ 8 _ 9 _ 0 _ 11 _ 12 _ 13 _ 14 _ 15_ 16 _ 17 _ 18 _ 19 _ 10 _ 11 _ 12 _ 13 _ 14 _ 15_ 16 _ 17 _ 18 _ 19 _ 10 _31 _ 32 _ 33 _34 _35 _36 _ 37 _ 38 _ 39 _ 30 _end_bmatrix]

这样的一个单通道的矩阵 4\*10   列数为10 elemChannel==10    ===》 truth.checkVector(10) 的结果为  4

那么我们可能会疑问 elemChannel的值可不可以为其他的值比如说：等于行数

尝试了一下：checkVector(4)===> -1

再来看这样的一个5\*10的矩阵：

![\\begin\{bmatrix\} 1 & 2 & 3 & 4 & 5 & 6 & 7 & 8 & 9 & 0 \\\\ 11 & 12 & 13 & 14 & 15& 16 & 17 & 18 & 19 & 10 \\\\ 11 & 12 & 13 & 14 & 15& 16 & 17 & 18 & 19 & 10 \\\\21& 22 & 23 &24 & 25 & 26 & 27 &28 & 29 &20 \\\\ 31 & 32 & 33 &34 &35 &36 & 37 & 38 & 39 & 30 \\end\{bmatrix\}][begin_bmatrix_ 1 _ 2 _ 3 _ 4 _ 5 _ 6 _ 7 _ 8 _ 9 _ 0 _ 11 _ 12 _ 13 _ 14 _ 15_ 16 _ 17 _ 18 _ 19 _ 10 _ 11 _ 12 _ 13 _ 14 _ 15_ 16 _ 17 _ 18 _ 19 _ 10 _21_ 22 _ 23 _24 _ 25 _ 26 _ 27 _28 _ 29 _20 _ 31 _ 32 _ 33 _34 _35 _36 _ 37 _ 38 _ 39 _ 30 _end_bmatrix]

这个是一个5\*10的一个单通道矩阵 ，checkVector(10）=5

所以单通道的矩阵  n\*m   checkVector(m)=n

那么对于多通道的呢，我们继续来看双通道的矩阵

# 双通道矩阵： #

elemChannel==2

Mat truth = new Mat(20, 1, CvType.CV_8UC2);    
        	System.out.println(truth.checkVector(2));//   result:20
    
    
            Mat truth = new Mat(1, 20, CvType.CV_8UC2);    
        	System.out.println(truth.checkVector(2));//   result:20

对于双通道矩阵，m\*n  m和n 中必须有一个为 1的

如果m ==1 则 checkVector(2)==n

如果n ==1 则 checkVector(2)==m

否则 checkVector== -1

# 三通道矩阵： #

elemChannel=3

Mat truth = new Mat(1, 20, CvType.CV_8UC3);    
        	System.out.println(truth.checkVector(3));//   result:20
    
    		Mat truth = new Mat(20, 1, CvType.CV_8UC3);    
        	System.out.println(truth.checkVector(3));//   result:20

对于双通道矩阵，m\*n  m和n 中必须有一个为 1的

如果m ==1 则 checkVector(3)==n

如果n ==1 则 checkVector(3)==m

否则 checkVector== -1

多通道矩阵

Mat truth = new Mat(20, 1, CvType.CV_8UC(10));    
        System.out.println(truth.checkVector(10));//   result:20
    		
        Mat truth = new Mat(1, 20, CvType.CV_8UC(10));    
        System.out.println(truth.checkVector(10));//   result:20

类似双，三通道矩阵 elemChannel 的值为通道数  并且m\*n中其中一个为1

那么checkVector的值我们都知道了，opencv 设置这样的一个函数有什么作用

The official OpenCV's doc says:

> [`cv::Mat::checkVector()`][cv_Mat_checkVector] returns N if the matrix is 1-channel (N x ptdim) or ptdim-channel (1 x N) or (N x 1); negative number otherwise

OpenCV considers some data types equivalent in case of some functions i.e. `objectPoints` of [`cv::solvePnP()`][cv_solvePnP] can be:

*  1xN/Nx1 1-channel `cv::Mat`
 *  3xN/Nx3 3-channel `cv::Mat`
 *  `std::vector<cv::Point3f>`

With `checkVector` you can make sure that you are passing the correct representation of your data.

大概的意思是说，在opencv中有些函数是要求参数满足一些特定的形式，比如：[`solvePnP`][cv_solvePnP]函数，checkVector 就是为了确保你传入的数据满足特定的形式

继续看：

truth.checkVector(elemChannels, depth);

elemChannel 通道元素数量

depth 深度

Mat 的深度是类型决定的，不同的类型对应不同的深度，深度反应出图像颜色像素值

深度的值：

CV\_8U = 0,  
            CV\_8S = 1,  
            CV\_16U = 2,  
            CV\_16S = 3,  
            CV\_32S = 4,  
            CV\_32F = 5,  
            CV\_64F = 6,  
            CV\_16F = 7;

Mat truth = new Mat(1, 20, CvType.CV_32FC2); 
           //  depth ！=mat.depth()   
    	    System.out.println(truth.checkVector(2,5));//result 20
    
    	    Mat truth = new Mat(1, 20, CvType.CV_32FC2); 
          //  depth ！=mat.depth()   
    	    System.out.println(truth.checkVector(2,0));//result -1

truth.checkVector(int elemChannels, int depth, boolean requireContinuous);

elemChannel 通道元素数量

depth 深度

requireContinuous  是否连续  （目前我知道的mat 经过submat 获取到的矩阵是不连续的，没有经过submat的矩阵是连续的）

通过上面的，我们可以看到的是checkVector 这个函数是为了检验mat 是否满足某些条件

int Mat::checkVector(int _elemChannels, int _depth, bool _requireContinuous) const
    {
        return data && (depth() == _depth || _depth <= 0) &&
            (isContinuous() || !_requireContinuous) &&
            ((dims == 2 && (((rows == 1 || cols == 1) && channels() == _elemChannels) ||
                            (cols == _elemChannels && channels() == 1))) ||
            (dims == 3 && channels() == 1 && size.p[2] == _elemChannels && (size.p[0] == 1 || size.p[1] == 1) &&
             (isContinuous() || step.p[1] == step.p[2]*size.p[2])))
        ? (int)(total()*channels()/_elemChannels) : -1;
    }

我们看checkVector的源码 也是如此，如果不满足条件则返回 -1 如果满足条件则返回一个正数

上面是我对checkVector这个函数的理解

希望对你有所帮助！

[begin_bmatrix_ 1 _ 2 _ 3 _ 4 _ 5 _ 6 _ 7 _ 8 _ 9 _ 0 _ 11 _ 12 _ 13 _ 14 _ 15_ 16 _ 17 _ 18 _ 19 _ 10 _ 11 _ 12 _ 13 _ 14 _ 15_ 16 _ 17 _ 18 _ 19 _ 10 _31 _ 32 _ 33 _34 _35 _36 _ 37 _ 38 _ 39 _ 30 _end_bmatrix]: https://latex.codecogs.com/gif.latex?%5Cbegin%7Bbmatrix%7D%201%20%26%202%20%26%203%20%26%204%20%26%205%20%26%206%20%26%207%20%26%208%20%26%209%20%26%200%20%5C%5C%2011%20%26%2012%20%26%2013%20%26%2014%20%26%2015%26%2016%20%26%2017%20%26%2018%20%26%2019%20%26%2010%20%5C%5C%2011%20%26%2012%20%26%2013%20%26%2014%20%26%2015%26%2016%20%26%2017%20%26%2018%20%26%2019%20%26%2010%20%5C%5C31%20%26%2032%20%26%2033%20%2634%20%2635%20%2636%20%26%2037%20%26%2038%20%26%2039%20%26%2030%20%5Cend%7Bbmatrix%7D
[begin_bmatrix_ 1 _ 2 _ 3 _ 4 _ 5 _ 6 _ 7 _ 8 _ 9 _ 0 _ 11 _ 12 _ 13 _ 14 _ 15_ 16 _ 17 _ 18 _ 19 _ 10 _ 11 _ 12 _ 13 _ 14 _ 15_ 16 _ 17 _ 18 _ 19 _ 10 _21_ 22 _ 23 _24 _ 25 _ 26 _ 27 _28 _ 29 _20 _ 31 _ 32 _ 33 _34 _35 _36 _ 37 _ 38 _ 39 _ 30 _end_bmatrix]: https://latex.codecogs.com/gif.latex?%5Cbegin%7Bbmatrix%7D%201%20%26%202%20%26%203%20%26%204%20%26%205%20%26%206%20%26%207%20%26%208%20%26%209%20%26%200%20%5C%5C%2011%20%26%2012%20%26%2013%20%26%2014%20%26%2015%26%2016%20%26%2017%20%26%2018%20%26%2019%20%26%2010%20%5C%5C%2011%20%26%2012%20%26%2013%20%26%2014%20%26%2015%26%2016%20%26%2017%20%26%2018%20%26%2019%20%26%2010%20%5C%5C21%26%2022%20%26%2023%20%2624%20%26%2025%20%26%2026%20%26%2027%20%2628%20%26%2029%20%2620%20%5C%5C%2031%20%26%2032%20%26%2033%20%2634%20%2635%20%2636%20%26%2037%20%26%2038%20%26%2039%20%26%2030%20%5Cend%7Bbmatrix%7D
[cv_Mat_checkVector]: http://docs.opencv.org/master/d3/d63/classcv_1_1Mat.html#a39541d4dbd7fafbfae93f1737e51ffbc
[cv_solvePnP]: http://docs.opencv.org/master/d9/d0c/group__calib3d.html#ga549c2075fac14829ff4a58bc931c033d