text: /**
   * @function Geometric_Transforms_Demo.cpp
   * @brief Demo code for Geometric Transforms
   * @author OpenCV team
   */
  
  #include "opencv2/imgcodecs.hpp"
  #include "opencv2/highgui.hpp"
  #include "opencv2/imgproc.hpp"
  #include <iostream>
  
  using namespace cv;
  using namespace std;
  
  /// Global variables
  const char* source_window = "Source image";
  const char* warp_window = "Warp";
  const 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
    CommandLineParser parser( argc, argv, "{@input | ../data/lena.jpg | input image}" );
    src = imread( parser.get<String>( "@input" ), IMREAD_COLOR );
    if( src.empty() )
    {
        cout << "Could not open or find the image!\n" << endl;
        cout << "Usage: " << argv[0] << " <Input image>" << endl;
        return -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.f, 0 );
    srcTri[2] = Point2f( 0, src.rows - 1.f );
  
    dstTri[0] = Point2f( src.cols*0.0f, src.rows*0.33f );
    dstTri[1] = Point2f( src.cols*0.85f, src.rows*0.25f );
    dstTri[2] = Point2f( src.cols*0.15f, src.rows*0.7f );
  
    /// 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;
  
    /// Get the rotation matrix with the specifications above
    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, WINDOW_AUTOSIZE );
    imshow( source_window, src );
  
    namedWindow( warp_window, WINDOW_AUTOSIZE );
    imshow( warp_window, warp_dst );
  
    namedWindow( warp_rotate_window, WINDOW_AUTOSIZE );
    imshow( warp_rotate_window, warp_rotate_dst );
  
    /// Wait until user exits the program
    waitKey(0);
  
    return 0;
  }
  