Adding 11-02 example

example_11-02.cpp

@@ -0,0 +1,47 @@
+// Example 11-2. Code for perspective transformation
+// Compute a perspective transformation between the 4 src control points
+// in srcQuad to 4 dst control points in dstQuad and apply it the image.
+
+#include <opencv2/opencv.hpp>
+#include <iostream>
+
+using namespace std;
+
+int main(int argc, char** argv) {
+
+  if(argc != 2) {
+    cout << "Perspective Warp\nUsage: " <<argv[0] <<" <imagename>\n" << endl;
+    return -1;
+  }
+
+  cv::Mat src = cv::imread(argv[1],1);
+  if( src.empty() ) { cout << "Can not load " << argv[1] << endl; return -1; }
+
+  cv::Point2f srcQuad[] = {
+    cv::Point2f(0, 0),                   // src Top left
+    cv::Point2f(src.cols-1, 0),          // src Top right
+    cv::Point2f(src.cols-1, src.rows-1), // src Bottom right
+    cv::Point2f(0, src.rows-1)           // src Bottom left
+  };
+
+  cv::Point2f dstQuad[] = {
+    cv::Point2f(src.cols*0.05f, src.rows*0.33f),
+    cv::Point2f(src.cols*0.9f, src.rows*0.25f),
+    cv::Point2f(src.cols*0.8f, src.rows*0.9f),
+    cv::Point2f(src.cols*0.2f, src.rows*0.7f)
+  };
+
+  // COMPUTE PERSPECTIVE MATRIX
+  //
+  cv::Mat warp_mat = cv::getPerspectiveTransform(srcQuad, dstQuad);
+  cv::Mat dst;
+  cv::warpPerspective(src, dst, warp_mat, src.size(), cv::INTER_LINEAR,
+                      cv::BORDER_CONSTANT, cv::Scalar());
+
+  for( int i = 0; i < 4; i++ )
+    cv::circle(dst, dstQuad[i], 5, cv::Scalar(255, 0, 255), -1, cv::LINE_AA);
+
+  cv::imshow("Perspective Transform Test", dst);
+  cv::waitKey();
+  return 0;
+}