flip函数
Flips a 2D array around vertical, horizontal, or both axes.
-
C++: void flip(InputArraysrc, OutputArraydst, int flipCode)
C: void cvFlip(const CvArr*src, CvArr*dst=NULL, intflip_mode=0)
Parameters:
- src - input array
- dst - output array of the same size and type as src.
- 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 (see the discussion below for the formulas).
The function flip flips the array in one of three different ways (row and column indices are 0-based):
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 orflipCode==0).
（上述对函数Flip描述来自 <<The OpenCV Reference Manual,Release2.4.3>> P.130-P.131）
测试代码：
// CookbookMatImage.cpp : Defines the entry point for the console application.
// The cookbook: Computer Vision Programming using the OpenCV Library.
// by Robert Laganiere, Packt Publishing, 2011.
// Copyright (C) 2013-2015 Gavin Liu, http://blog.csdn.net/songzitea
#include "stdafx.h"
#include "opencv2\core\core.hpp"
#include "opencv2\highgui\highgui.hpp"
int main()
{
cv::Mat image;// create image
cv::Mat result;
image = cv::imread("monument.jpg");// open image
// check if image has been successfully read
if (!image.data)return 0;
cv:: cv::flip(image,result,1);
cv::namedWindow("Flip Image"); // define the window
cv::imshow("Flip Image", result); // display the Flip image
cv::waitKey(0);// wait for key pressed
}
测试输出结果：
原始图像
不同参数flipCode如下图所示：
图1 flopcode 大于0
图2 flopcode等于0
图3 flopcode小于0
如果我们在.NET+OpenCV中进行对图像反转时，我们可以使用flip函数中的flipCode参数达到简单的反转目的。
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