opencv/samples/cpp/tutorial_code/Basic/Drawing_1.cpp

/**
 * @file Drawing_1.cpp
 * @brief Simple sample code
 */

#include <opencv2/core/core.hpp>
#include <opencv2/highgui/highgui.hpp>

#define w 400

using namespace cv;

/// Function headers
void MyEllipse( Mat img, double angle );
void MyFilledCircle( Mat img, Point center );
void MyPolygon( Mat img );
void MyLine( Mat img, Point start, Point end );

/**
 * @function main
 * @brief Main function
 */
int main( int argc, char **argv ){

  /// Windows names
  char atom_window[] = "Drawing 1: Atom";
  char rook_window[] = "Drawing 2: Rook";

  /// Create black empty images 
  Mat atom_image = Mat::zeros( w, w, CV_8UC3 );
  Mat rook_image = Mat::zeros( w, w, CV_8UC3 );

  /// 1. Draw a simple atom:
  /// -----------------------

  /// 1.a. Creating ellipses 
  MyEllipse( atom_image, 90 );
  MyEllipse( atom_image, 0 );
  MyEllipse( atom_image, 45 );
  MyEllipse( atom_image, -45 );

  /// 1.b. Creating circles
  MyFilledCircle( atom_image, Point( w/2.0, w/2.0) );

  /// 2. Draw a rook
  /// ------------------

  /// 2.a. Create a convex polygon
  MyPolygon( rook_image );

  /// 2.b. Creating rectangles
  rectangle( rook_image,
	     Point( 0, 7*w/8.0 ),
	     Point( w, w),
	     Scalar( 0, 255, 255 ),
	     -1,
	     8 );

  /// 2.c. Create a few lines 
  MyLine( rook_image, Point( 0, 15*w/16 ), Point( w, 15*w/16 ) );
  MyLine( rook_image, Point( w/4, 7*w/8 ), Point( w/4, w ) );
  MyLine( rook_image, Point( w/2, 7*w/8 ), Point( w/2, w ) );
  MyLine( rook_image, Point( 3*w/4, 7*w/8 ), Point( 3*w/4, w ) );

  /// 3. Display your stuff!
  imshow( atom_window, atom_image );
  cvMoveWindow( atom_window, 0, 200 );
  imshow( rook_window, rook_image );
  cvMoveWindow( rook_window, w, 200 );

  waitKey( 0 );
  return(0);
}

/// Function Declaration

/**
 * @function MyEllipse
 * @brief Draw a fixed-size ellipse with different angles
 */
void MyEllipse( Mat img, double angle )
{
  int thickness = 2;
  int lineType = 8;

  ellipse( img,
	   Point( w/2.0, w/2.0 ),
	   Size( w/4.0, w/16.0 ),
	   angle,
	   0, 
	   360,
	   Scalar( 255, 0, 0 ),
	   thickness,
	   lineType );  
}

/**
 * @function MyFilledCircle
 * @brief Draw a fixed-size filled circle
 */
void MyFilledCircle( Mat img, Point center )
{
  int thickness = -1;
  int lineType = 8;

  circle( img, 
	  center,
	  w/32.0,
	  Scalar( 0, 0, 255 ),
	  thickness, 
	  lineType );
}

/**
 * @function MyPolygon
 * @function Draw a simple concave polygon (rook)
 */
void MyPolygon( Mat img )
{
  int lineType = 8;

  /** Create some points */
  Point rook_points[1][20];
  rook_points[0][0] = Point( w/4.0, 7*w/8.0 );
  rook_points[0][1] = Point( 3*w/4.0, 7*w/8.0 );
  rook_points[0][2] = Point( 3*w/4.0, 13*w/16.0 );
  rook_points[0][3] = Point( 11*w/16.0, 13*w/16.0 );
  rook_points[0][4] = Point( 19*w/32.0, 3*w/8.0 );
  rook_points[0][5] = Point( 3*w/4.0, 3*w/8.0 );
  rook_points[0][6] = Point( 3*w/4.0, w/8.0 );
  rook_points[0][7] = Point( 26*w/40.0, w/8.0 );
  rook_points[0][8] = Point( 26*w/40.0, w/4.0 );
  rook_points[0][9] = Point( 22*w/40.0, w/4.0 );
  rook_points[0][10] = Point( 22*w/40.0, w/8.0 );
  rook_points[0][11] = Point( 18*w/40.0, w/8.0 );
  rook_points[0][12] = Point( 18*w/40.0, w/4.0 );
  rook_points[0][13] = Point( 14*w/40.0, w/4.0 );
  rook_points[0][14] = Point( 14*w/40.0, w/8.0 );
  rook_points[0][15] = Point( w/4.0, w/8.0 );
  rook_points[0][16] = Point( w/4.0, 3*w/8.0 );
  rook_points[0][17] = Point( 13*w/32.0, 3*w/8.0 );
  rook_points[0][18] = Point( 5*w/16.0, 13*w/16.0 );
  rook_points[0][19] = Point( w/4.0, 13*w/16.0) ;

  const Point* ppt[1] = { rook_points[0] };
  int npt[] = { 20 };

  fillPoly( img,
	    ppt,
	    npt,
            1,
	    Scalar( 255, 255, 255 ),
	    lineType );			
}

/**
 * @function MyLine
 * @brief Draw a simple line
 */
void MyLine( Mat img, Point start, Point end )
{
  int thickness = 2;
  int lineType = 8;
  line( img, 
	start,
	end,
	Scalar( 0, 0, 0 ),
	thickness,
	lineType );
}