Opencv透视变换综合实例详解

#include<opencv2\opencv.hpp>
using namespace cv;
using namespace std;
int main(int arc, char** argv) { 
 Mat src = imread("1.jpg");
 namedWindow("input", CV_WINDOW_AUTOSIZE);
 imshow("input", src);
 //灰度化
 Mat grayImg;
 cvtColor(src, grayImg, CV_BGR2GRAY);
 //二值化
 Mat binaryImg;
 threshold(grayImg, binaryImg, 0, 255, THRESH_BINARY_INV | THRESH_OTSU);
 //闭操作
 Mat kernel = getStructuringElement(MORPH_RECT,Size(3,3));
 morphologyEx(binaryImg, binaryImg, MORPH_CLOSE,kernel,Point(-1,-1) ,3);
 imshow("output", binaryImg);
 //寻找轮廓
 Mat draw = Mat::zeros(src.size(), CV_8UC3);
 vector<vector<Point>>contours;
 findContours(binaryImg, contours, RETR_EXTERNAL, CHAIN_APPROX_SIMPLE, Point());
 for (int i = 0; i < contours.size(); i++) {
 Rect rect = boundingRect(contours[i]);
 if (rect.width < src.cols / 2 && rect.height < src.rows / 2)continue;
 drawContours(draw, contours, i, Scalar(0, 0, 255), 2);
 }
 imshow("output2", draw);
 //霍夫直线检测
 vector<Vec4i> lines;
 cvtColor(draw, draw, CV_BGR2GRAY);
 HoughLinesP(draw, lines, 1, CV_PI / 180, src.rows/2,src.rows/2,0);
 Mat draw2 = Mat::zeros(src.size(), CV_8UC3);
 for (int j = 0; j < lines.size(); j++) {
 Vec4i ln = lines[j];
 line(draw2, Point(ln[0], ln[1]), Point(ln[2], ln[3]), Scalar(0, 255, 0), 2); 
 }
 printf("number of line:%d\n", lines.size());
 imshow("output3", draw2);
 //寻找与定位直线
 Vec4i topLine,bottomLine,leftLine,rightLine;
 for (int j = 0; j < lines.size(); j++) {
 Vec4i ln = lines[j];
 if (ln[1] < src.rows / 2 && ln[3] < src.rows / 2) {
  topLine = ln;
 }
 if (ln[1] > src.rows / 2 && ln[3] > src.rows / 2) {
  bottomLine = ln;
 }
 if (ln[0] < src.cols / 2 && ln[2] < src.cols / 2) {
  leftLine = ln;
 }
 if (ln[0] > src.cols / 2 && ln[2] > src.cols / 2) {
  rightLine = ln;
 }
 }
 cout << "topLine:p1(x,y)=" << topLine[0] << "," << topLine[1]<<" " << "p2(x,y)=" << topLine[2] << "," << topLine[3] << endl;
 cout << "bottomLine:p1(x,y)=" << bottomLine[0] << "," << bottomLine[1] << " " << "p2(x,y)=" << bottomLine[2] << "," << bottomLine[3] << endl;
 cout << "leftLine:p1(x,y)=" << leftLine[0] << "," << leftLine[1] << " " << "p2(x,y)=" << leftLine[2] << "," << leftLine[3] << endl;
 cout << "rightLine:p1(x,y)=" << rightLine[0] << "," << rightLine[1] << " " << "p2(x,y)=" << rightLine[2] << "," << rightLine[3] << endl;
 //求解直线方程
 float k1, c1;
 k1 = float((topLine[3] - topLine[1])) / float(topLine[2] - topLine[0]);
 c1 = topLine[1] - k1*topLine[0];
 float k2, c2;
 k2 = float((bottomLine[3] - bottomLine[1])) / float(bottomLine[2] - bottomLine[0]);
 c2 = bottomLine[1] - k2*bottomLine[0];
 float k3, c3;
 k3 = float((leftLine[3] - leftLine[1])) / float(leftLine[2] - leftLine[0]);
 c3 = leftLine[1] - k3*leftLine[0];
 float k4, c4;
 k4 = float((rightLine[3] - rightLine[1])) / float(rightLine[2] - rightLine[0]);
 c4 = rightLine[1] - k4*rightLine[0];
 //求解直线交点
 Point p1;
 p1.x = (int)((c1 - c3) / (k3 - k1));
 p1.y = (int)(k1*p1.x + c1);
 Point p2;
 p2.x = (int)((c1 - c4) / (k4 - k1));
 p2.y = (int)(k1*p2.x + c1);
 Point p3;
 p3.x = (int)((c2 - c4) / (k4 - k2));
 p3.y = (int)(k2*p3.x + c2);
 Point p4;
 p4.x = (int)((c2 - c3) / (k3 - k2));
 p4.y = (int)(k2*p4.x + c2);
 cout << "左上角：" << p1.x << "," << p1.y << endl;
 cout << "右上角：" << p2.x << "," << p2.y << endl;
 cout << "右下角：" << p3.x << "," << p3.y << endl;
 cout << "左下角：" << p4.x << "," << p4.y << endl;
 //画出交点
 circle(draw2, p1, 2, Scalar(0, 0, 255));
 circle(draw2, p2, 2, Scalar(0, 0, 255));
 circle(draw2, p3, 2, Scalar(0, 0, 255));
 circle(draw2, p4, 2, Scalar(0, 0, 255));
 imshow("output4", draw2);
 //透视变换
 vector<Point2f> srcCorners(4);
 srcCorners[0] = p1;
 srcCorners[1] = p2;
 srcCorners[2] = p3;
 srcCorners[3] = p4;
 vector<Point2f> dstCorners(4);
 dstCorners[0] = Point(0, 0);
 dstCorners[1] = Point(src.cols, 0);
 dstCorners[2] = Point(src.cols, src.rows);
 dstCorners[3] = Point(0, src.rows); 
 Mat warpMartrix = getPerspectiveTransform(srcCorners, dstCorners);//Mat warpMartrix = findHomography(srcCorners, dstCorners); 
 Mat result = Mat::zeros(src.size(), -1);
 warpPerspective(src, result, warpMartrix, result.size(),INTER_LINEAR);
 imshow("output5", result);
 waitKey(0);
 return 0; 
}