opencv中flip函数

函数声明

/** @brief Flips a 2D array around vertical, horizontal, or both axes.

The function cv::flip flips the array in one of three different ways (row
and column indices are 0-based):
\f[\texttt{dst} _{ij} =
\left\{
\begin{array}{l l}
\texttt{src} _{\texttt{src.rows}-i-1,j} & if\;  \texttt{flipCode} = 0 \\
\texttt{src} _{i, \texttt{src.cols} -j-1} & if\;  \texttt{flipCode} > 0 \\
\texttt{src} _{ \texttt{src.rows} -i-1, \texttt{src.cols} -j-1} & if\; \texttt{flipCode} < 0 \\
\end{array}
\right.\f]
The example scenarios of using the function are the following:
*   Vertical flipping of the image (flipCode == 0) to switch between
    top-left and bottom-left image origin. This is a typical operation
    in video processing on Microsoft Windows\* OS.
*   Horizontal flipping of the image with the subsequent horizontal
    shift and absolute difference calculation to check for a
    vertical-axis symmetry (flipCode \> 0).
*   Simultaneous horizontal and vertical flipping of the image with
    the subsequent shift and absolute difference calculation to check
    for a central symmetry (flipCode \< 0).
*   Reversing the order of point arrays (flipCode \> 0 or
    flipCode == 0).
@param src input array.
@param dst output array of the same size and type as src.
@param flipCode a flag to specify how to flip the array; 0 means
flipping around the x-axis and positive value (for example, 1) means
flipping around y-axis. Negative value (for example, -1) means flipping
around both axes.
@sa transpose , repeat , completeSymm
*/
CV_EXPORTS_W void flip(InputArray src, OutputArray dst, int flipCode);

测试demo

	Mat srcImage = imread("../sources/cat.jpg");
    Mat flipImage;
    flip(srcImage, flipImage, -1);
    imshow("flipImage", flipImage);
    waitKey(0);

总结

函数声明中注释很详细，当第三个参数：
flipCode == 0 垂直翻转
flipCode > 0 水平翻转
flipCode < 0 同时进行垂直和水平翻转