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