基本绘图

目录

• 目标
• OpenCV 理论
  • 点 (Point)
  • Scalar
• 代码
• 原理解释
• 结果

下一个教程： 使用 OpenCV 生成随机数和文本

原作者	Ana Huamán
兼容性	OpenCV >= 3.0

目标

在本教程中，你将学习如何：

• 使用 OpenCV 函数 line() 绘制一条直线
• 使用 OpenCV 函数 ellipse() 绘制一个椭圆
• 使用 OpenCV 函数 rectangle() 绘制一个矩形
• 使用 OpenCV 函数 circle() 绘制一个圆
• 使用 OpenCV 函数 fillPoly() 绘制一个填充的多边形

OpenCV 理论

C++

在本教程中，我们将大量使用两个结构：cv::Point 和 cv::Scalar

Java

在本教程中，我们将大量使用两个结构：cv::Point 和 cv::Scalar

Python

在本教程中，我们将在 Python 中大量使用元组，而不是 cv::Point 和 cv::Scalar

Point (点)

它表示一个二维点，由其图像坐标 \(x\) 和 \(y\) 指定。我们可以将其定义为

C++

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

或者

Point pt = Point(10, 8);

Java

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

或者

Point pt = new Point(10, 8);

Python

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

Scalar (标量)

• 表示一个四元向量。Scalar 类型在 OpenCV 中广泛用于传递像素值。
• 在本教程中，我们将广泛使用它来表示 BGR 颜色值（3 个参数）。如果最后一个参数不打算使用，则无需定义。
• 让我们看一个例子，如果要求提供颜色参数，而我们给出
  C++

  Scalar( a, b, c )

  Java

  Scalar( a, b, c )

  Python

  ( a, b, c )

  我们将定义一种 BGR 颜色，例如：蓝色 = a，绿色 = b，红色 = c

代码

C++

• 此代码位于您的 OpenCV 示例文件夹中。否则，您可以从 这里 获取

   
  #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

• 此代码位于您的 OpenCV 示例文件夹中。否则，您可以从 这里 获取

  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) {
          // 加载本地库。
  System.loadLibrary(Core.NATIVE_LIBRARY_NAME);
          new GeometricDrawingRun().run();
      }
  }

Python

• 此代码位于您的 OpenCV 示例文件夹中。否则，您可以从 这里 获取

  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
   
      # 创建一些点
  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)
      # 只绘制线条会是
      # 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"
   
  # 创建黑色空白图像
  size = W, W, 3
  atom_image = np.zeros(size, dtype=np.uint8)
  rook_image = np.zeros(size, dtype=np.uint8)
   
   
  # 1.a. 创建椭圆
  my_ellipse(atom_image, 90)
  my_ellipse(atom_image, 0)
  my_ellipse(atom_image, 45)
  my_ellipse(atom_image, -45)
   
  # 1.b. 创建圆
  my_filled_circle(atom_image, (W // 2, W // 2))
   
   
  # 2. 绘制一个车子
  # ------------------
  # 2.a. 创建一个凸多边形
  my_polygon(rook_image)
   
  cv.rectangle(rook_image,
  (0, 7 * W // 8),
  (W, W),
                (0, 255, 255),
                -1,
                8)
   
   
  # 2.c. 创建几条线
  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()

解释

由于我们计划绘制两个示例（一个原子和一个车子），因此我们需要创建两个图像和两个窗口来显示它们。

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"
 
# 创建黑色空白图像
size = W, W, 3
atom_image = np.zeros(size, dtype=np.uint8)
rook_image = np.zeros(size, dtype=np.uint8)

我们创建了函数来绘制不同的几何形状。例如，为了绘制原子，我们使用了 MyEllipse 和 MyFilledCircle

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. 创建椭圆
my_ellipse(atom_image, 90)
my_ellipse(atom_image, 0)
my_ellipse(atom_image, 45)
my_ellipse(atom_image, -45)
 
# 1.b. 创建圆
my_filled_circle(atom_image, (W // 2, W // 2))

为了绘制车子，我们使用了 MyLine、rectangle 和 MyPolygon

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. 绘制一个车子
# ------------------
# 2.a. 创建一个凸多边形
my_polygon(rook_image)
 
cv.rectangle(rook_image,
(0, 7 * W // 8),
(W, W),
              (0, 255, 255),
              -1,
              8)
 
 
# 2.c. 创建几条线
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))

让我们看看这些函数内部有什么

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)

• 如我们所见，MyLine 仅调用 line() 函数，该函数执行以下操作
  • 从点 start 到点 end 绘制一条线
  • 该线显示在图像 img 中
  • 线的颜色由 ( 0, 0, 0 ) 定义，这是对应于 黑色 的 RGB 值
  • 线的粗细设置为 thickness（在此例中为 2）
  • 该线是 8 连接的（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)

• 从上面的代码，我们可以看出 ellipse() 函数绘制一个椭圆，如下所示
  • 椭圆显示在图像 img 中
  • 椭圆的中心位于点 (w/2, w/2)，并被包含在一个大小为 (w/4, w/16) 的框中
  • 椭圆旋转 angle 度
  • 椭圆在 0 到 360 度之间延伸一个弧
  • 图形的颜色将是 ( 255, 0, 0 )，在 BGR 值中表示蓝色。
  • 椭圆的 粗细 为 2。

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)

• 与 ellipse 函数类似，我们可以看出 *circle* 接收的参数如下
  • 将显示圆的图像 (img)
  • 圆的中心由点 center 表示
  • 圆的半径：w/32
  • 圆的颜色：( 0, 0, 255 )，在 BGR 中表示*红色*
  • 由于 thickness = -1，圆将绘制为填充状态。

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
 
    # 创建一些点
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)
    # 只绘制线条会是
    # cv.polylines(img, [ppt], True, (255, 0, 255), line_type)

• 为了绘制一个填充的多边形，我们使用 fillPoly() 函数。我们注意到
  • 多边形将在 img 上绘制
  • 多边形的顶点是 ppt 中的点集
  • 多边形的颜色由 ( 255, 255, 255 ) 定义，这是*白色*的 BGR 值

rectangle (矩形)

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)

• 最后是 cv::rectangle 函数（我们没有为它创建特殊的函数）。我们注意到
  • 矩形将在 rook_image 上绘制
  • 矩形的两个对角顶点由 ( 0, 7*w/8 ) 和 ( w, w ) 定义
  • 矩形的颜色由 ( 0, 255, 255 ) 给出，这是*黄色*的 BGR 值
  • 由于粗细值由 FILLED (-1) 指定，因此矩形将被填充。

结果

编译并运行您的程序，应该会得到类似下面的结果