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上面是原图，以下是利用坐标映射后的结果url=OvyNHG3WKjwxbiJDOWund5lfoAPXkxXdzSyFcQqI3NKsJZkqOZjlPegJ4DG75vOosupgaM3iklTPnq3TSzHnZq
fr=aladdin
Image1中的点1。2，3相应到了Image2中的点1，2。3。这样我们就能得到仿射矩阵。于是Image1中的全部点都能通过这个仿射矩阵映射到Image2中
仿射变换后
在做图像增强时。我们改变的时图像的值域,g(x)output f(x)是input h是我们的方法，比方对照度增强直方图均衡化 用g(x) = h(f(x))
可是在坐标变换，改变的是定义域， g(x) = f(h(x))
如果我们有源图像f和坐标映射函数h,我们要怎么计算输出图像g呢？
procedure forwardWarp(f,h,outg):
For every pixelxinf(x)
1. Compute the destination locationx′=h(x).
2. Copy the pixelf(x)tog(x′).
procedure inverseWarp(f,h,outg):
For every pixelx′ing(x′)
1. Compute the source locationx=h?(x′)
2. Resamplef(x)at
locationx
and copy tog(x′)
遍历输出图像的点。映射到源图像，再去取点。
映射函数h就是原来h的逆矩阵。
当然了，也会碰到非整数的情况，接下来还要作一些别的处理。就不细述。
一眼就能看出。我们的映射函数是
获得我们的变换矩阵M
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附上官方的sample
仿射矩阵.
).#include "opencv2/imgproc.hpp"
#include <iostream>
#include "opencv2/highgui.hpp"
using namespace cv;
using namespace std;
/// Global variables
char* source_window = "Source image";
char* warp_window = "Warp";
char* warp_rotate_window = "Warp + Rotate";
/** @function main */
int main( int argc, char** argv )
{
Point2f srcTri[3];
Point2f dstTri[3];
Mat rot_mat( 2, 3, CV_32FC1 );
Mat warp_mat( 2, 3, CV_32FC1 );
Mat src, warp_dst, warp_rotate_dst;
/// Load the image
src = imread( argv[1], 1 );
/// Set the dst image the same type and size as src
warp_dst = Mat::zeros( src.rows, src.cols, src.type() );
/// Set your 3 points to calculate the Affine Transform
srcTri[0] = Point2f( 0,0 );
srcTri[1] = Point2f( src.cols - 1, 0 );
srcTri[2] = Point2f( 0, src.rows - 1 );
dstTri[0] = Point2f( src.cols*0.0, src.rows*0.33 );
dstTri[1] = Point2f( src.cols*0.85, src.rows*0.25 );
dstTri[2] = Point2f( src.cols*0.15, src.rows*0.7 );
/// Get the Affine Transform
warp_mat = getAffineTransform( srcTri, dstTri );
/// Apply the Affine Transform just found to the src image
warpAffine( src, warp_dst, warp_mat, warp_dst.size() );
/** Rotating the image after Warp */
/// Compute a rotation matrix with respect to the center of the image
Point center = Point( warp_dst.cols/2, warp_dst.rows/2 );
double angle = -50.0;
double scale = 0.6;
/// 这里获得旋转矩阵，中心是center,角度为－50度，并缩放为原来的0.6倍，也是简单的样例
rot_mat = getRotationMatrix2D( center, angle, scale );
/// Rotate the warped image
warpAffine( warp_dst, warp_rotate_dst, rot_mat, warp_dst.size() );
/// Show what you got
namedWindow( source_window, CV_WINDOW_AUTOSIZE );
imshow( source_window, src );
namedWindow( warp_window, CV_WINDOW_AUTOSIZE );
imshow( warp_window, warp_dst );
namedWindow( warp_rotate_window, CV_WINDOW_AUTOSIZE );
imshow( warp_rotate_window, warp_rotate_dst );
/// Wait until user exits the program
waitKey(0);
return 0;
}
怎样实现这种变换呢
for( int j = 0; j < src.rows; j++ ) {
for( int i = 0; i < src.cols; i++ ) {
map_x.at<float>(j,i) = src.cols - i ;
map_y.at<float>(j,i) = j ; }}然后再调用
remap( src, dst, map_x, map_y, INTER_LINEAR, BORDER_CONSTANT, Scalar(0,0, 0) );
#include "opencv2/highgui.hpp"
#include "opencv2/imgproc.hpp"
#include <iostream>
#include <stdio.h>
using namespace cv;
/// Global variables
Mat src, dst;
Mat map_x, map_y;
char* remap_window = "Remap demo";
int ind = 0;
/// Function Headers
void update_map( void );
/**
* @function main
*/
int main( int argc, char** argv )
{
/// Load the image
src = imread( argv[1], 1 );
/// Create dst, map_x and map_y with the same size as src:
dst.create( src.size(), src.type() );
map_x.create( src.size(), CV_32FC1 );
map_y.create( src.size(), CV_32FC1 );
/// Create window
namedWindow( remap_window, CV_WINDOW_AUTOSIZE );
/// Loop
while( true )
{
/// Each 1 sec. Press ESC to exit the program
int c = waitKey( 1000 );
if( (char)c == 27 )
{ break; }
/// Update map_x & map_y. Then apply remap
update_map();
remap( src, dst, map_x, map_y, CV_INTER_LINEAR, BORDER_CONSTANT, Scalar(0,0, 0) );
/// Display results
imshow( remap_window, dst );
}
return 0;
}
/**
* @function update_map
* @brief Fill the map_x and map_y matrices with 4 types of mappings
*/
void update_map( void )
{
ind = ind%4;
for( int j = 0; j < src.rows; j++ )
{ for( int i = 0; i < src.cols; i++ )
{
switch( ind )
{
case 0:
if( i > src.cols*0.25 && i < src.cols*0.75 && j > src.rows*0.25 && j < src.rows*0.75 )
{
map_x.at<float>(j,i) = 2*( i - src.cols*0.25 ) + 0.5 ;
map_y.at<float>(j,i) = 2*( j - src.rows*0.25 ) + 0.5 ;
}
else
{ map_x.at<float>(j,i) = 0 ;
map_y.at<float>(j,i) = 0 ;
}
break;
case 1:
map_x.at<float>(j,i) = i ;
map_y.at<float>(j,i) = src.rows - j ;
break;
case 2:
map_x.at<float>(j,i) = src.cols - i ;
map_y.at<float>(j,i) = j ;
break;
case 3:
map_x.at<float>(j,i) = src.cols - i ;
map_y.at<float>(j,i) = src.rows - j ;
break;
} // end of switch
}
}
ind++;
}#include "opencv2/highgui/highgui.hpp"
#include "opencv2/imgproc/imgproc.hpp"
#include <iostream>
#define K 1.1
using namespace cv;
// Global variables
Mat src, dst;
Mat map_x, map_y;
char* remap_window = "Remap demo";
void update_map( void );
int main( int argc, char** argv ) {
src = imread( argv[1], 1 );
dst.create( src.rows*K, src.cols*K, src.type() );
map_x.create( src.rows*K, src.cols*K, CV_32FC1 );
map_y.create( src.rows*K, src.cols*K, CV_32FC1 );
namedWindow( remap_window, CV_WINDOW_AUTOSIZE );
update_map();
remap( src, dst, map_x, map_y, INTER_LANCZOS4, BORDER_CONSTANT, Scalar(0, 0, 0) );
imshow( remap_window, dst );
waitKey(0);
return 0;
}
void update_map( void )
{
for( int j = 0; j < (int)(K*src.rows); j++ ) {
for( int i = 0; i < (int)(K*src.cols); i++ ) {
map_x.at<float>(j,i) = i/K;
map_y.at<float>(j,i) = j/K;
}
}
}
我们一開始就见到了这图片，那么怎么实现呢？#include "opencv2/highgui/highgui.hpp"
#include "opencv2/imgproc/imgproc.hpp"
#include <iostream>
using namespace cv;
using namespace std;
#define K 2 //表示取2个点
#define threshold 0.1 //缩放的程度
// Global variables
Mat src, src_copy, dst;
Mat map_x, map_y;
char* window = "Scale demo";
int samplePointNum = 0; //已经点了几次
Point myPoints[K]; //存放用户点击的坐标
bool flag = false; //点击2次，就设置flag,開始更新
void update_map( void )
{
int leftX = threshold*src.cols;
int rightX = src.cols - leftX;
int recLeftX = myPoints[0].x;
int recRightX = myPoints[1].x;
for( int j = 0; j < src.rows; j++ ) {
for( int i = 0; i < src.cols; i++ ) {
if(i > leftX && i < rightX) {
map_x.at<float>(j,i) = recLeftX + (i - leftX) * (recRightX - recLeftX)/(rightX - leftX);
map_y.at<float>(j,i) = j;
} else if(i <= leftX) {
map_x.at<float>(j,i) = i * recLeftX/leftX;
map_y.at<float>(j,i) = j;
} else {
map_x.at<float>(j,i) = recRightX + (i- rightX) * (src.cols - recRightX)/(src.cols - rightX);
map_y.at<float>(j,i) = j;
}
}
}
flag = true;
remap( src_copy, dst, map_x, map_y, INTER_LANCZOS4, BORDER_CONSTANT, Scalar(0, 0, 0) );
imshow( window, dst );
imwrite( "./result.jpg", dst );
return;
}
static void onMouse( int event, int x, int y, int, void* )
{
if(samplePointNum == K){
if(!flag)
update_map();
return;
}
if( event != EVENT_LBUTTONDOWN)
return;
rectangle(src, Point(x-3,y-3), Point(x+3,y+3), Scalar(255,0,0), 1);
myPoints[samplePointNum++] = Point(x,y);
imshow( window, src );
return;
}
int main( int argc, char** argv ) {
src = imread( argv[1], 1 );
src_copy = src.clone();
dst.create( src.rows, src.cols, src.type() );
map_x.create( src.rows, src.cols, CV_32FC1 );
map_y.create( src.rows, src.cols, CV_32FC1 );
namedWindow( window, CV_WINDOW_AUTOSIZE );
setMouseCallback( window, onMouse, 0 );
imshow( window, src );
waitKey(0);
return 0;
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原文地址：http://www.cnblogs.com/gcczhongduan/p/5276947.html
