在opencv3.4.1 這個版本中，這兩個函數的聲明在頭文件core.hpp中。
hconcat函數在opencv中有如下三個重載函數：
/** @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.
@sa cv::vconcat(const Mat*, size_t, OutputArray), @sa cv::vconcat(InputArrayOfArrays, OutputArray) and @sa cv::vconcat(InputArray, InputArray, OutputArray)
*/
CV_EXPORTS void hconcat(const Mat* src, size_t nsrc, OutputArray dst);
/** @overload
@code{.cpp}
cv::Mat_<float> A = (cv::Mat_<float>(3, 2) << 1, 4,
2, 5,
3, 6);
cv::Mat_<float> B = (cv::Mat_<float>(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.
*/
CV_EXPORTS void hconcat(InputArray src1, InputArray src2, OutputArray dst);
/** @overload
@code{.cpp}
std::vector<cv::Mat> 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.
*/
CV_EXPORTS_W void hconcat(InputArrayOfArrays src, OutputArray dst);
總結起來就一個要求，
all of the matrices must have the same number of rows and the same depth.
要進行圖像的水平連接，各個源圖像的行數（rows）必須相同（也就是圖像的高必須相等），並且圖像的通道數（depth）也需要相同。
vconcat也有三個重載函數如下：
/** @brief Applies vertical concatenation to given matrices.
The function vertically concatenates two or more cv::Mat matrices (with the same number of cols).
@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)
*/
CV_EXPORTS void vconcat(const Mat* src, size_t nsrc, OutputArray dst);
/** @overload
@code{.cpp}
cv::Mat_<float> A = (cv::Mat_<float>(3, 2) << 1, 7,
2, 8,
3, 9);
cv::Mat_<float> B = (cv::Mat_<float>(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.
*/
CV_EXPORTS void vconcat(InputArray src1, InputArray src2, OutputArray dst);
/** @overload
@code{.cpp}
std::vector<cv::Mat> 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.
*/
CV_EXPORTS_W void vconcat(InputArrayOfArrays src, OutputArray dst);
總結起來，要進行圖像的豎向的拼接，也只有一個要求：
all of the matrices must have the same number of cols and the same depth.
需要圖像的列數相等（即圖像的寬度是相等的，cols），並且圖像的通道數（depth）相等。