Affine transformation and perspective transformation __OPENCV

Affine transformation my understanding is that the image is rotated or stretched at different degrees on a two-dimensional plane, but no matter how it changes, his image is parallelogram, and its transformation function is a 2*3 matrix.

Perspective transformation is an observer who observes the image in a 3-D space from different angles, so the image is projected on the observer's two-dimensional plane, and its transformation function is 3*3, or 4*4 matrix.

The affine transformation code is as follows:

#include <cv.h> #include The pivot transformation code is as follows:


#include <cv.h> #include  


Using OPENCV2 to realize affine transformation


#include <opencv2/opencv.hpp> #include <opencv2/imgproc/imgproc.hpp> #include <iostream> using
namespace CV;
using namespace Std;
	int main () {point2f srctriangle[3];
	POINT2F Dsttriangle[3];
	Mat Rotmat (2,3,CV_32FC1);
	Mat Warpmat (2,3,CV_32FC1);
	Mat srcimage,dstimage_warp,dstimage_warp_rotate;
	Srcimage=imread ("1.jpg", 1);
	Dstimage_warp=mat::zeros (Srcimage.rows,srcimage.cols,srcimage.type ());  Affine transformations require only 3 points to determine, because the radial transformation is a parallelogram srctriangle[0]=point2f (0,0);  The lower left corner of the image is srctriangle[1]=point2f (static_cast<float> (srcimage.cols-1), 0);  The lower right corner of the image is srctriangle[2]=point2f (0,static_cast<float> (srcimage.rows-1)); The upper-left corner of the image is dsttriangle[0]=point2f (static_cast<float> (srcimage.cols*0.0),static_cast<float> ( srcimage.rows*0.33)); (0,0) The coordinate dsttriangle[1]=point2f (static_cast<float> (srcimage.cols*0.65),static_cast<float> ( srcimage.rows*0.35)); DSTTRIANGLE[2]=POINT2F (static_cast<float> (srcimage.cols*0.15),static_cast<float> (srcImage.rows*0.6));  Warpmat=getaffinetransform (Srctriangle,dsttriangle);  In fact, the transformation matrix is determined by the position before and after the four-angle transformation (the position of the Four Corners is given) warpaffine (Srcimage,dstimage_warp,warpmat,dstimage_warp.size ());  Using this transformed matrix to transform the image////Here you can imagine that the image is first arranged in a given rule (here is a point of four corners), and then the others are arranged according to this rule imshow ("Xiaoguo", Dstimage_warp); Show effect chart//----------------The second way-------------------------------point Center=point (Dstimage_warp.cols/2,dstimage_
	WARP.ROWS/2);
	Double angle=-30.0;
	Double scale=0.8; rotmat=getrotationmatrix2d (Center,angle,scale); The rotation matrix Warpaffine (Dstimage_warp,dstimage_warp_rotate,rotmat,dstimage_warp_rotate.size ()) is reduced by the center point, the rotation angle, and the contraction amplification small structure.
	Same as the previous face Imshow ("Xiaoguo2", dstimage_warp_rotate);
	Waitkey (0);
return 0; }