opencv-学习笔记

opencv——反转函数的定义

CV_EXPORTS_W void flip(InputArray src, OutputArray dst, int flipCode);

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

The function flip flips the array in one of three different ways (row
and column indices are 0-based):
f[	exttt{dst} _{ij} =
left{
egin{array}{l l}
	exttt{src} _{	exttt{src.rows}-i-1,j} & if;  	exttt{flipCode} = 0 \
	exttt{src} _{i, 	exttt{src.cols} -j-1} & if;  	exttt{flipCode} > 0 \
	exttt{src} _{ 	exttt{src.rows} -i-1, 	exttt{src.cols} -j-1} & if; 	exttt{flipCode} < 0 \
end{array}

ight.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
*/

现在讨论其中的参数InputArray和OutputArray。

 nputArray这个接口类可以是Mat、Mat_<T>、Mat_<T, m, n>、vector<T>、vector<vector<T>>、vector<Mat>。也就意味着当你看refman或者源代码时，如果看见函数的参数类型是InputArray型时，把上诉几种类型作为参数都是可以的。

有时候InputArray输入的矩阵是个空参数，你只需要用cv：：noArray（）作为参数即可，或者很多代码里都用cv：：Mat（）作为空参。

这个类只能作为函数的形参参数使用，不要试图声明一个InputArray类型的变量

https://blog.csdn.net/yang_xian521/article/details/7755101