opencv图像水平/竖直拼接hconcat()/vconcat()

图像水平拼接hconcat（）

hconcat函数在opencv中有如下三个重载函数：

1. CV_EXPORTS void hconcat(const Mat src, size_t nsrc, OutputArray dst);*

/** @brief Applies horizontal concatenation to given matrices.

The function horizontally concatenates two or more cv::Mat matrices (with the same number of rows).
@code{.cpp}
    cv::Mat matArray[] = { cv::Mat(4, 1, CV_8UC1, cv::Scalar(1)),
                           cv::Mat(4, 1, CV_8UC1, cv::Scalar(2)),
                           cv::Mat(4, 1, CV_8UC1, cv::Scalar(3)),};

    cv::Mat out;
    cv::hconcat( matArray, 3, out );
    //out:
    //[1, 2, 3;
    // 1, 2, 3;
    // 1, 2, 3;
    // 1, 2, 3]
@endcode
@param src input array or vector of matrices. all of the matrices must have the same number of rows and the same depth.
@param nsrc number of matrices in src.
@param dst output array. It has the same number of rows and depth as the src, and the sum of cols of the src.
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2. CV_EXPORTS void hconcat(InputArray src1, InputArray src2, OutputArray dst);

 @code{.cpp}
    cv::Mat_ A = (cv::Mat_(3, 2) << 1, 4,
                                                  2, 5,
                                                  3, 6);
    cv::Mat_ B = (cv::Mat_(3, 2) << 7, 10,
                                                  8, 11,
                                                  9, 12);

    cv::Mat C;
    cv::hconcat(A, B, C);
    //C:
    //[1, 4, 7, 10;
    // 2, 5, 8, 11;
    // 3, 6, 9, 12]
 @endcode
 @param src1 first input array to be considered for horizontal concatenation.
 @param src2 second input array to be considered for horizontal concatenation.
 @param dst output array. It has the same number of rows and depth as the src1 and src2, and the sum of cols of the src1 and src2.
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3.CV_EXPORTS_W void hconcat(InputArrayOfArrays src, OutputArray dst);

/** @overload
 @code{.cpp}
    std::vector matrices = { cv::Mat(4, 1, CV_8UC1, cv::Scalar(1)),
                                      cv::Mat(4, 1, CV_8UC1, cv::Scalar(2)),
                                      cv::Mat(4, 1, CV_8UC1, cv::Scalar(3)),};

    cv::Mat out;
    cv::hconcat( matrices, out );
    //out:
    //[1, 2, 3;
    // 1, 2, 3;
    // 1, 2, 3;
    // 1, 2, 3]
 @endcode
 @param src input array or vector of matrices. all of the matrices must have the same number of rows and the same depth.
 @param dst output array. It has the same number of rows and depth as the src, and the sum of cols of the src.
same depth.
 */
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总结起来就一个要求，
all of the matrices must have the same number of rows and the same depth.
要进行图像的水平连接，各个源图像的行数（rows）必须相同（也就是图像的高必须相等），并且图像的通道数（depth）也需要相同。

图像垂直拼接vconcat（）

有三个重载函数：
1. CV_EXPORTS void vconcat(const Mat src, size_t nsrc, OutputArray dst);*

@code{.cpp}
    cv::Mat matArray[] = { cv::Mat(1, 4, CV_8UC1, cv::Scalar(1)),
                           cv::Mat(1, 4, CV_8UC1, cv::Scalar(2)),
                           cv::Mat(1, 4, CV_8UC1, cv::Scalar(3)),};

    cv::Mat out;
    cv::vconcat( matArray, 3, out );
    //out:
    //[1,   1,   1,   1;
    // 2,   2,   2,   2;
    // 3,   3,   3,   3]
@endcode
@param src input array or vector of matrices. all of the matrices must have the same number of cols and the same depth.
@param nsrc number of matrices in src.
@param dst output array. It has the same number of cols and depth as the src, and the sum of rows of the src.
@sa cv::hconcat(const Mat*, size_t, OutputArray), @sa cv::hconcat(InputArrayOfArrays, OutputArray) and @sa cv::hconcat(InputArray, InputArray, OutputArray)
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2. CV_EXPORTS void vconcat(InputArray src1, InputArray src2, OutputArray dst);

/** @overload
 @code{.cpp}
    cv::Mat_ A = (cv::Mat_(3, 2) << 1, 7,
                                                  2, 8,
                                                  3, 9);
    cv::Mat_ B = (cv::Mat_(3, 2) << 4, 10,
                                                  5, 11,
                                                  6, 12);

    cv::Mat C;
    cv::vconcat(A, B, C);
    //C:
    //[1, 7;
    // 2, 8;
    // 3, 9;
    // 4, 10;
    // 5, 11;
    // 6, 12]
 @endcode
 @param src1 first input array to be considered for vertical concatenation.
 @param src2 second input array to be considered for vertical concatenation.
 @param dst output array. It has the same number of cols and depth as the src1 and src2, and the sum of rows of the src1 and src2.
 */
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3. CV_EXPORTS_W void vconcat(InputArrayOfArrays src, OutputArray dst);

/** @overload
 @code{.cpp}
    std::vector matrices = { cv::Mat(1, 4, CV_8UC1, cv::Scalar(1)),
                                      cv::Mat(1, 4, CV_8UC1, cv::Scalar(2)),
                                      cv::Mat(1, 4, CV_8UC1, cv::Scalar(3)),};

    cv::Mat out;
    cv::vconcat( matrices, out );
    //out:
    //[1,   1,   1,   1;
    // 2,   2,   2,   2;
    // 3,   3,   3,   3]
 @endcode
 @param src input array or vector of matrices. all of the matrices must have the same number of cols and the same depth
 @param dst output array. It has the same number of cols and depth as the src, and the sum of rows of the src.
same depth.
 */
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总结起来，要进行图像的竖向的拼接，也只有一个要求：
all of the matrices must have the same number of cols and the same depth.
需要图像的列数相等（即图像的宽度是相等的，cols），并且图像的通道数（depth）相等。

参考链接：
opencv hconcat和vconcat函数详解
OpenCV双目相机的标定C++