基本的な描画

目次

• 目標
• OpenCV Theory
  • Point
  • Scalar
• コード
• 説明
• 結果

次のチュートリアル: OpenCVによる乱数生成とテキスト描画

原著者	Ana Huamán
互換性	OpenCV >= 3.0

目標

このチュートリアルでは、以下の方法を学ぶ:

• OpenCV関数 line() を使って直線を描く
• OpenCV関数 ellipse() を使って楕円を描く
• OpenCV関数 rectangle() を使って矩形を描く
• OpenCV関数 circle() を使って円を描く
• OpenCV関数 fillPoly() を使って塗りつぶした多角形を描く

OpenCVの理論

C++

このチュートリアルでは、主に2つの構造体 cv::Point と cv::Scalar を多用する :

Java

このチュートリアルでは、主に2つの構造体 cv::Point と cv::Scalar を多用する :

Python

このチュートリアルでは、cv::Point や cv::Scalar の代わりに、Pythonのタプルを多用する :

Point

画像座標 \(x\) と \(y\) で指定される2次元の点を表す。次のように定義できる:

C++

Point pt;
pt.x = 10;
pt.y = 8;

または

Point pt =  Point(10, 8);

Java

Point pt = new Point();
pt.x = 10;
pt.y = 8;

または

Point pt = new Point(10, 8);

Python

pt = (10, 0) # x = 10, y = 0

Scalar

• 4要素のベクトルを表す。型Scalarは、ピクセル値を渡す目的でOpenCVにおいて広く使われている。
• このチュートリアルでは、BGRの色値（3つの引数）を表すためにこれを多用する。使わない場合、最後の引数は定義しなくてよい。
• 例を見てみよう。色の引数を求められて次のように指定すると:
  C++

  Scalar( a, b, c )

  Java

  Scalar( a, b, c )

  Python

  ( a, b, c )

  次のようなBGRの色を定義していることになる: Blue = a、Green = b、Red = c

コード

C++

• このコードはOpenCVのサンプルフォルダにある。なければ こちら

   
  #include <opencv2/core.hpp>
  #include <opencv2/imgproc.hpp>
  #include <opencv2/highgui.hpp>
   
  #define w 400
   
  using namespace cv;
   
  void MyEllipse( Mat img, double angle );
  void MyFilledCircle( Mat img, Point center );
  void MyPolygon( Mat img );
  void MyLine( Mat img, Point start, Point end );
   
  int main( void ){
   
   char atom_window[] = "Drawing 1: Atom";
   char rook_window[] = "Drawing 2: Rook";
   
   Mat atom_image = Mat::zeros( w, w, CV_8UC3 );
   Mat rook_image = Mat::zeros( w, w, CV_8UC3 );
   
   
   MyEllipse( atom_image, 90 );
   MyEllipse( atom_image, 0 );
   MyEllipse( atom_image, 45 );
   MyEllipse( atom_image, -45 );
   
   MyFilledCircle( atom_image, Point( w/2, w/2) );
   
   
   MyPolygon( rook_image );
   
   rectangle( rook_image,
   Point( 0, 7*w/8 ),
   Point( w, w),
   Scalar( 0, 255, 255 ),
   FILLED,
   LINE_8 );
   
   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 ) );
   
   imshow( atom_window, atom_image );
   moveWindow( atom_window, 0, 200 );
   imshow( rook_window, rook_image );
   moveWindow( rook_window, w, 200 );
   
   waitKey( 0 );
   return(0);
  }
   
   
  void MyEllipse( Mat img, double angle )
  {
   int thickness = 2;
   int lineType = 8;
   
   ellipse( img,
   Point( w/2, w/2 ),
   Size( w/4, w/16 ),
   angle,
   0,
   360,
   Scalar( 255, 0, 0 ),
   thickness,
   lineType );
  }
   
  void MyFilledCircle( Mat img, Point center )
  {
   circle( img,
   center,
   w/32,
   Scalar( 0, 0, 255 ),
   FILLED,
   LINE_8 );
  }
   
  void MyPolygon( Mat img )
  {
   int lineType = LINE_8;
   
   Point rook_points[1][20];
   rook_points[0][0] = Point( w/4, 7*w/8 );
   rook_points[0][1] = Point( 3*w/4, 7*w/8 );
   rook_points[0][2] = Point( 3*w/4, 13*w/16 );
   rook_points[0][3] = Point( 11*w/16, 13*w/16 );
   rook_points[0][4] = Point( 19*w/32, 3*w/8 );
   rook_points[0][5] = Point( 3*w/4, 3*w/8 );
   rook_points[0][6] = Point( 3*w/4, w/8 );
   rook_points[0][7] = Point( 26*w/40, w/8 );
   rook_points[0][8] = Point( 26*w/40, w/4 );
   rook_points[0][9] = Point( 22*w/40, w/4 );
   rook_points[0][10] = Point( 22*w/40, w/8 );
   rook_points[0][11] = Point( 18*w/40, w/8 );
   rook_points[0][12] = Point( 18*w/40, w/4 );
   rook_points[0][13] = Point( 14*w/40, w/4 );
   rook_points[0][14] = Point( 14*w/40, w/8 );
   rook_points[0][15] = Point( w/4, w/8 );
   rook_points[0][16] = Point( w/4, 3*w/8 );
   rook_points[0][17] = Point( 13*w/32, 3*w/8 );
   rook_points[0][18] = Point( 5*w/16, 13*w/16 );
   rook_points[0][19] = Point( w/4, 13*w/16 );
   
   const Point* ppt[1] = { rook_points[0] };
   int npt[] = { 20 };
   
   fillPoly( img,
   ppt,
   npt,
   1,
   Scalar( 255, 255, 255 ),
   lineType );
  }
   
  void MyLine( Mat img, Point start, Point end )
  {
   int thickness = 2;
   int lineType = LINE_8;
   
   line( img,
   start,
   end,
   Scalar( 0, 0, 0 ),
   thickness,
   lineType );
  }

Java

• このコードはOpenCVのサンプルフォルダにある。なければ こちら

  import org.opencv.core.*;
  import org.opencv.core.Point;
  import org.opencv.highgui.HighGui;
  import org.opencv.imgproc.Imgproc;
   
  import java.util.*;
  import java.util.List;
   
  class GeometricDrawingRun{
   
   private static final int W = 400;
   
   public void run(){
   String atom_window = "Drawing 1: Atom";
   String rook_window = "Drawing 2: Rook";
   
   Mat atom_image = Mat.zeros( W, W, CvType.CV_8UC3 );
   Mat rook_image = Mat.zeros( W, W, CvType.CV_8UC3 );
   
   MyEllipse( atom_image, 90.0 );
   MyEllipse( atom_image, 0.0 );
   MyEllipse( atom_image, 45.0 );
   MyEllipse( atom_image, -45.0 );
   
   MyFilledCircle( atom_image, new Point( W/2, W/2) );
   
   MyPolygon( rook_image );
   
   Imgproc.rectangle( rook_image,
   new Point( 0, 7*W/8 ),
   new Point( W, W),
   new Scalar( 0, 255, 255 ),
   -1,
   8,
   0 );
   
   MyLine( rook_image, new Point( 0, 15*W/16 ), new Point( W, 15*W/16 ) );
   MyLine( rook_image, new Point( W/4, 7*W/8 ), new Point( W/4, W ) );
   MyLine( rook_image, new Point( W/2, 7*W/8 ), new Point( W/2, W ) );
   MyLine( rook_image, new Point( 3*W/4, 7*W/8 ), new Point( 3*W/4, W ) );
   
   HighGui.imshow( atom_window, atom_image );
   HighGui.moveWindow( atom_window, 0, 200 );
   HighGui.imshow( rook_window, rook_image );
   HighGui.moveWindow( rook_window, W, 200 );
   
   HighGui.waitKey( 0 );
   System.exit(0);
   }
   
   
   private void MyEllipse( Mat img, double angle ) {
   int thickness = 2;
   int lineType = 8;
   int shift = 0;
   
   Imgproc.ellipse( img,
   new Point( W/2, W/2 ),
   new Size( W/4, W/16 ),
   angle,
   0.0,
   360.0,
   new Scalar( 255, 0, 0 ),
   thickness,
   lineType,
   shift );
   }
   
   private void MyFilledCircle( Mat img, Point center ) {
   int thickness = -1;
   int lineType = 8;
   int shift = 0;
   
   Imgproc.circle( img,
   center,
   W/32,
   new Scalar( 0, 0, 255 ),
   thickness,
   lineType,
   shift );
   }
   
   private void MyPolygon( Mat img ) {
   int lineType = 8;
   int shift = 0;
   
   Point[] rook_points = new Point[20];
   rook_points[0] = new Point( W/4, 7*W/8 );
   rook_points[1] = new Point( 3*W/4, 7*W/8 );
   rook_points[2] = new Point( 3*W/4, 13*W/16 );
   rook_points[3] = new Point( 11*W/16, 13*W/16 );
   rook_points[4] = new Point( 19*W/32, 3*W/8 );
   rook_points[5] = new Point( 3*W/4, 3*W/8 );
   rook_points[6] = new Point( 3*W/4, W/8 );
   rook_points[7] = new Point( 26*W/40, W/8 );
   rook_points[8] = new Point( 26*W/40, W/4 );
   rook_points[9] = new Point( 22*W/40, W/4 );
   rook_points[10] = new Point( 22*W/40, W/8 );
   rook_points[11] = new Point( 18*W/40, W/8 );
   rook_points[12] = new Point( 18*W/40, W/4 );
   rook_points[13] = new Point( 14*W/40, W/4 );
   rook_points[14] = new Point( 14*W/40, W/8 );
   rook_points[15] = new Point( W/4, W/8 );
   rook_points[16] = new Point( W/4, 3*W/8 );
   rook_points[17] = new Point( 13*W/32, 3*W/8 );
   rook_points[18] = new Point( 5*W/16, 13*W/16 );
   rook_points[19] = new Point( W/4, 13*W/16 );
   
   MatOfPoint matPt = new MatOfPoint();
   matPt.fromArray(rook_points);
   
   List<MatOfPoint> ppt = new ArrayList<MatOfPoint>();
   ppt.add(matPt);
   
   Imgproc.fillPoly(img,
   ppt,
   new Scalar( 255, 255, 255 ),
   lineType,
   shift,
   new Point(0,0) );
   }
   
   private void MyLine( Mat img, Point start, Point end ) {
   int thickness = 2;
   int lineType = 8;
   int shift = 0;
   
   Imgproc.line( img,
   start,
   end,
   new Scalar( 0, 0, 0 ),
   thickness,
   lineType,
   shift );
   }
  }
   
  public class BasicGeometricDrawing {
   public static void main(String[] args) {
   // Load the native library.
   System.loadLibrary(Core.NATIVE_LIBRARY_NAME);
   new GeometricDrawingRun().run();
   }
  }

Python

• このコードはOpenCVのサンプルフォルダにある。なければ こちら

  import cv2 as cv
  import numpy as np
   
  W = 400
   
  def my_ellipse(img, angle):
   thickness = 2
   line_type = 8
   
   cv.ellipse(img,
   (W // 2, W // 2),
   (W // 4, W // 16),
   angle,
   0,
   360,
   (255, 0, 0),
   thickness,
   line_type)
   
  def my_filled_circle(img, center):
   thickness = -1
   line_type = 8
   
   cv.circle(img,
   center,
   W // 32,
   (0, 0, 255),
   thickness,
   line_type)
   
  def my_polygon(img):
   line_type = 8
   
   # Create some points
   ppt = np.array([[W / 4, 7 * W / 8], [3 * W / 4, 7 * W / 8],
   [3 * W / 4, 13 * W / 16], [11 * W / 16, 13 * W / 16],
   [19 * W / 32, 3 * W / 8], [3 * W / 4, 3 * W / 8],
   [3 * W / 4, W / 8], [26 * W / 40, W / 8],
   [26 * W / 40, W / 4], [22 * W / 40, W / 4],
   [22 * W / 40, W / 8], [18 * W / 40, W / 8],
   [18 * W / 40, W / 4], [14 * W / 40, W / 4],
   [14 * W / 40, W / 8], [W / 4, W / 8],
   [W / 4, 3 * W / 8], [13 * W / 32, 3 * W / 8],
   [5 * W / 16, 13 * W / 16], [W / 4, 13 * W / 16]], np.int32)
   ppt = ppt.reshape((-1, 1, 2))
   cv.fillPoly(img, [ppt], (255, 255, 255), line_type)
   # Only drawind the lines would be:
   # cv.polylines(img, [ppt], True, (255, 0, 255), line_type)
   
  def my_line(img, start, end):
   thickness = 2
   line_type = 8
   
   cv.line(img,
   start,
   end,
   (0, 0, 0),
   thickness,
   line_type)
   
  atom_window = "Drawing 1: Atom"
  rook_window = "Drawing 2: Rook"
   
  # Create black empty images
  size = W, W, 3
  atom_image = np.zeros(size, dtype=np.uint8)
  rook_image = np.zeros(size, dtype=np.uint8)
   
   
  # 1.a. Creating ellipses
  my_ellipse(atom_image, 90)
  my_ellipse(atom_image, 0)
  my_ellipse(atom_image, 45)
  my_ellipse(atom_image, -45)
   
  # 1.b. Creating circles
  my_filled_circle(atom_image, (W // 2, W // 2))
   
   
  # 2. Draw a rook
  # ------------------
  # 2.a. Create a convex polygon
  my_polygon(rook_image)
   
  cv.rectangle(rook_image,
   (0, 7 * W // 8),
   (W, W),
   (0, 255, 255),
   -1,
   8)
   
   
  # 2.c. Create a few lines
  my_line(rook_image, (0, 15 * W // 16), (W, 15 * W // 16))
  my_line(rook_image, (W // 4, 7 * W // 8), (W // 4, W))
  my_line(rook_image, (W // 2, 7 * W // 8), (W // 2, W))
  my_line(rook_image, (3 * W // 4, 7 * W // 8), (3 * W // 4, W))
   
  cv.imshow(atom_window, atom_image)
  cv.moveWindow(atom_window, 0, 200)
  cv.imshow(rook_window, rook_image)
  cv.moveWindow(rook_window, W, 200)
   
  cv.waitKey(0)
  cv.destroyAllWindows()

説明

ここでは2つの例（原子と城）を描く予定なので、それらを表示するために2つの画像と2つのウィンドウを作成する必要がある。

C++

 char atom_window[] = "Drawing 1: Atom";
 char rook_window[] = "Drawing 2: Rook";
 
 Mat atom_image = Mat::zeros( w, w, CV_8UC3 );
 Mat rook_image = Mat::zeros( w, w, CV_8UC3 );

Java

 String atom_window = "Drawing 1: Atom";
 String rook_window = "Drawing 2: Rook";
 
        Mat atom_image = Mat.zeros( W, W, CvType.CV_8UC3 );
        Mat rook_image = Mat.zeros( W, W, CvType.CV_8UC3 );

Python

atom_window = "Drawing 1: Atom"
rook_window = "Drawing 2: Rook"
 
# Create black empty images
size = W, W, 3
atom_image = np.zeros(size, dtype=np.uint8)
rook_image = np.zeros(size, dtype=np.uint8)

さまざまな幾何学的図形を描くための関数を作成した。たとえば原子を描くには、MyEllipse と MyFilledCircle を使った:

C++

  MyEllipse( atom_image, 90 );
  MyEllipse( atom_image, 0 );
  MyEllipse( atom_image, 45 );
  MyEllipse( atom_image, -45 );
 
  MyFilledCircle( atom_image, Point( w/2, w/2) );

Java

        MyEllipse( atom_image, 90.0 );
        MyEllipse( atom_image, 0.0 );
        MyEllipse( atom_image, 45.0 );
        MyEllipse( atom_image, -45.0 );
 
        MyFilledCircle( atom_image, new Point( W/2, W/2) );

Python

 
# 1.a. Creating ellipses
my_ellipse(atom_image, 90)
my_ellipse(atom_image, 0)
my_ellipse(atom_image, 45)
my_ellipse(atom_image, -45)
 
# 1.b. Creating circles
my_filled_circle(atom_image, (W // 2, W // 2))

そして城を描くには、MyLine、rectangle、および MyPolygon を使った:

C++

  MyPolygon( rook_image );
 
 rectangle( rook_image,
 Point( 0, 7*w/8 ),
 Point( w, w),
 Scalar( 0, 255, 255 ),
         FILLED,
         LINE_8 );
 
  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 ) );

Java

        MyPolygon( rook_image );
 
        Imgproc.rectangle( rook_image,
 new Point( 0, 7*W/8 ),
 new Point( W, W),
 new Scalar( 0, 255, 255 ),
                -1,
                8,
                0 );
 
        MyLine( rook_image, new Point( 0, 15*W/16 ), new Point( W, 15*W/16 ) );
        MyLine( rook_image, new Point( W/4, 7*W/8 ), new Point( W/4, W ) );
        MyLine( rook_image, new Point( W/2, 7*W/8 ), new Point( W/2, W ) );
        MyLine( rook_image, new Point( 3*W/4, 7*W/8 ), new Point( 3*W/4, W ) );

Python

 
# 2. Draw a rook
# ------------------
# 2.a. Create a convex polygon
my_polygon(rook_image)
 
cv.rectangle(rook_image,
              (0, 7 * W // 8),
              (W, W),
              (0, 255, 255),
              -1,
              8)
 
 
#  2.c. Create a few lines
my_line(rook_image, (0, 15 * W // 16), (W, 15 * W // 16))
my_line(rook_image, (W // 4, 7 * W // 8), (W // 4, W))
my_line(rook_image, (W // 2, 7 * W // 8), (W // 2, W))
my_line(rook_image, (3 * W // 4, 7 * W // 8), (3 * W // 4, W))

これらの各関数の中身を確認しよう:

C++

MyLine

C++

void MyLine( Mat img, Point start, Point end )
{
 int thickness = 2;
 int lineType = LINE_8;
 
 line( img,
    start,
    end,
 Scalar( 0, 0, 0 ),
    thickness,
    lineType );
}

Java

 private void MyLine( Mat img, Point start, Point end ) {
 int thickness = 2;
 int lineType = 8;
 int shift = 0;
 
        Imgproc.line( img,
                start,
                end,
 new Scalar( 0, 0, 0 ),
                thickness,
                lineType,
                shift );
    }

Python

def my_line(img, start, end):
    thickness = 2
    line_type = 8
 
 cv.line(img,
             start,
             end,
             (0, 0, 0),
             thickness,
             line_type)

• As we can see, MyLine just call the function line() , which does the following:
  • 点 start から点 end まで直線を描く
  • 直線は画像 img 上に表示される
  • 直線の色は ( 0, 0, 0 ) で定義され、これは 黒 に対応するRGB値である
  • 直線の太さは thickness（この場合は2）に設定される
  • 直線は8連結である（lineType = 8）

MyEllipse

C++

void MyEllipse( Mat img, double angle )
{
 int thickness = 2;
 int lineType = 8;
 
 ellipse( img,
 Point( w/2, w/2 ),
 Size( w/4, w/16 ),
       angle,
       0,
       360,
 Scalar( 255, 0, 0 ),
       thickness,
       lineType );
}

Java

 private void MyEllipse( Mat img, double angle ) {
 int thickness = 2;
 int lineType = 8;
 int shift = 0;
 
        Imgproc.ellipse( img,
 new Point( W/2, W/2 ),
 new Size( W/4, W/16 ),
                angle,
                0.0,
                360.0,
 new Scalar( 255, 0, 0 ),
                thickness,
                lineType,
                shift );
    }

Python

def my_ellipse(img, angle):
    thickness = 2
    line_type = 8
 
 cv.ellipse(img,
                (W // 2, W // 2),
                (W // 4, W // 16),
                angle,
                0,
                360,
                (255, 0, 0),
                thickness,
                line_type)

• From the code above, we can observe that the function ellipse() draws an ellipse such that:
  • 楕円は画像 img 上に表示される
  • 楕円の中心は点 (w/2, w/2) に位置し、サイズ (w/4, w/16) のボックスに収まる
  • 楕円は angle 度だけ回転される
  • 楕円は 0 度から 360 度までの円弧を描く
  • 図形の色は ( 255, 0, 0 ) であり、BGR値で青を意味する。
  • 楕円の thickness は2である。

MyFilledCircle

C++

void MyFilledCircle( Mat img, Point center )
{
 circle( img,
      center,
      w/32,
 Scalar( 0, 0, 255 ),
      FILLED,
      LINE_8 );
}

Java

 private void MyFilledCircle( Mat img, Point center ) {
 int thickness = -1;
 int lineType = 8;
 int shift = 0;
 
        Imgproc.circle( img,
                center,
                W/32,
 new Scalar( 0, 0, 255 ),
                thickness,
                lineType,
                shift );
    }

Python

def my_filled_circle(img, center):
    thickness = -1
    line_type = 8
 
 cv.circle(img,
               center,
               W // 32,
               (0, 0, 255),
               thickness,
               line_type)

• Similar to the ellipse function, we can observe that circle receives as arguments:
  • 円を描画する画像 (img)
  • 点 center で表される円の中心
  • 円の半径: w/32
  • 円の色: ( 0, 0, 255 )。これはBGRで赤 (Red)を意味する
  • thickness = -1 なので、円は塗りつぶして描画される。

MyPolygon

C++

void MyPolygon( Mat img )
{
 int lineType = LINE_8;
 
 Point rook_points[1][20];
  rook_points[0][0]  = Point(    w/4,   7*w/8 );
  rook_points[0][1]  = Point(  3*w/4,   7*w/8 );
  rook_points[0][2]  = Point(  3*w/4,  13*w/16 );
  rook_points[0][3]  = Point( 11*w/16, 13*w/16 );
  rook_points[0][4]  = Point( 19*w/32,  3*w/8 );
  rook_points[0][5]  = Point(  3*w/4,   3*w/8 );
  rook_points[0][6]  = Point(  3*w/4,     w/8 );
  rook_points[0][7]  = Point( 26*w/40,    w/8 );
  rook_points[0][8]  = Point( 26*w/40,    w/4 );
  rook_points[0][9]  = Point( 22*w/40,    w/4 );
  rook_points[0][10] = Point( 22*w/40,    w/8 );
  rook_points[0][11] = Point( 18*w/40,    w/8 );
  rook_points[0][12] = Point( 18*w/40,    w/4 );
  rook_points[0][13] = Point( 14*w/40,    w/4 );
  rook_points[0][14] = Point( 14*w/40,    w/8 );
  rook_points[0][15] = Point(    w/4,     w/8 );
  rook_points[0][16] = Point(    w/4,   3*w/8 );
  rook_points[0][17] = Point( 13*w/32,  3*w/8 );
  rook_points[0][18] = Point(  5*w/16, 13*w/16 );
  rook_points[0][19] = Point(    w/4,  13*w/16 );
 
 const Point* ppt[1] = { rook_points[0] };
 int npt[] = { 20 };
 
 fillPoly( img,
        ppt,
        npt,
        1,
 Scalar( 255, 255, 255 ),
        lineType );
}

Java

 private void MyPolygon( Mat img ) {
 int lineType = 8;
 int shift = 0;
 
 Point[] rook_points = new Point[20];
        rook_points[0]  = new Point(     W/4, 7*W/8   );
        rook_points[1]  = new Point(   3*W/4, 7*W/8   );
        rook_points[2]  = new Point(   3*W/4, 13*W/16 );
        rook_points[3]  = new Point( 11*W/16, 13*W/16 );
        rook_points[4]  = new Point( 19*W/32, 3*W/8   );
        rook_points[5]  = new Point(   3*W/4, 3*W/8   );
        rook_points[6]  = new Point(   3*W/4, W/8     );
        rook_points[7]  = new Point( 26*W/40, W/8     );
        rook_points[8]  = new Point( 26*W/40, W/4     );
        rook_points[9]  = new Point( 22*W/40, W/4     );
        rook_points[10] = new Point( 22*W/40, W/8     );
        rook_points[11] = new Point( 18*W/40, W/8     );
        rook_points[12] = new Point( 18*W/40, W/4     );
        rook_points[13] = new Point( 14*W/40, W/4     );
        rook_points[14] = new Point( 14*W/40, W/8     );
        rook_points[15] = new Point(     W/4, W/8     );
        rook_points[16] = new Point(     W/4, 3*W/8   );
        rook_points[17] = new Point( 13*W/32, 3*W/8   );
        rook_points[18] = new Point(  5*W/16, 13*W/16 );
        rook_points[19] = new Point(     W/4, 13*W/16 );
 
        MatOfPoint matPt = new MatOfPoint();
        matPt.fromArray(rook_points);
 
        List<MatOfPoint> ppt = new ArrayList<MatOfPoint>();
        ppt.add(matPt);
 
        Imgproc.fillPoly(img,
                ppt,
 new Scalar( 255, 255, 255 ),
                lineType,
                shift,
 new Point(0,0) );
    }

Python

def my_polygon(img):
    line_type = 8
 
 # Create some points
    ppt = np.array([[W / 4, 7 * W / 8], [3 * W / 4, 7 * W / 8],
                    [3 * W / 4, 13 * W / 16], [11 * W / 16, 13 * W / 16],
                    [19 * W / 32, 3 * W / 8], [3 * W / 4, 3 * W / 8],
                    [3 * W / 4, W / 8], [26 * W / 40, W / 8],
                    [26 * W / 40, W / 4], [22 * W / 40, W / 4],
                    [22 * W / 40, W / 8], [18 * W / 40, W / 8],
                    [18 * W / 40, W / 4], [14 * W / 40, W / 4],
                    [14 * W / 40, W / 8], [W / 4, W / 8],
                    [W / 4, 3 * W / 8], [13 * W / 32, 3 * W / 8],
                    [5 * W / 16, 13 * W / 16], [W / 4, 13 * W / 16]], np.int32)
    ppt = ppt.reshape((-1, 1, 2))
 cv.fillPoly(img, [ppt], (255, 255, 255), line_type)
 # Only drawind the lines would be:
 # cv.polylines(img, [ppt], True, (255, 0, 255), line_type)

• To draw a filled polygon we use the function fillPoly() . We note that:
  • 多角形は img 上に描画される
  • 多角形の頂点は ppt に含まれる点の集合である
  • 多角形の色は ( 255, 255, 255 ) で定義され、これは白 (white)のBGR値である

rectangle

C++

 rectangle( rook_image,
 Point( 0, 7*w/8 ),
 Point( w, w),
 Scalar( 0, 255, 255 ),
         FILLED,
         LINE_8 );

Java

        Imgproc.rectangle( rook_image,
 new Point( 0, 7*W/8 ),
 new Point( W, W),
 new Scalar( 0, 255, 255 ),
                -1,
                8,
                0 );

Python

cv.rectangle(rook_image,
              (0, 7 * W // 8),
              (W, W),
              (0, 255, 255),
              -1,
              8)

• Finally we have the cv::rectangle function (we did not create a special function for this guy). We note that:
  • 矩形は rook_image 上に描画される
  • 矩形の対角に位置する2つの頂点は ( 0, 7*w/8 ) と ( w, w ) で定義される
  • 矩形の色は ( 0, 255, 255 ) で与えられ、これは黄 (yellow)のBGR値である
  • thicknessの値が FILLED (-1) で与えられているため、矩形は塗りつぶされる。

結果

プログラムをコンパイルして実行すると、次のような結果が得られるはずである: