OpenCV 4.9基本绘图

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目标

在本教程中，您将学习如何：

使用 OpenCV 函数 line() 画一条线
使用 OpenCV 函数 ellipse()绘制椭圆
使用 OpenCV 函数 rectangle()绘制矩形
使用 OpenCV 函数 circle() 画一个圆
使用 OpenCV 函数 fillPoly()绘制填充多边形

OpenCV理论

在本教程中，我们将大量使用两种结构：cv::P oint 和 cv::Scalar ：

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;

Java:

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

C++:

Point pt = Point(10, 8);

Java:

Point pt = new Point(10, 8);

标量

表示一个 4 元素向量。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）。如果不打算使用最后一个参数，则无需定义它。
让我们看一个例子，如果我们被要求一个颜色参数，我们给出：

```
Scalar( a, b, c )
```
我们将定义一个 BGR 颜色，例如：蓝色 = a、绿色 = b 和红色 = c

代码
此代码位于 OpenCV 示例文件夹中。否则你可以从这里下载

C++:

#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:

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 :

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()

解释

由于我们计划绘制两个示例（一个原子和一个车），我们必须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:

# Windows names
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)

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：

 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. Draw a simple atom:
# -----------------------
 
# 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))

为了绘制车，我们使用了 MyLine、矩形和 MyPolygon：

 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))

让我们检查一下这些函数中的每一个都包含什么：

我的线条：

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)

正如我们所看到的，MyLine 只需调用函数 line（） ，它执行以下操作：
- 从点起点到点终点画一条线
- 该线显示在图像 img 中
- 线条颜色由 （ 0， 0， 0 ） 定义，它是与黑色相对应的 RGB 值
- 线条粗细设置为粗细（在本例中为 2）
- 该线是 8 连接的线（lineType = 8）

MyEllipse（椭圆）

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)

从上面的代码中，我们可以观察到函数 ellipse（） 绘制一个椭圆，使得：
- 椭圆显示在图像 img 中
- 椭圆中心位于点 （w/2， w/2） 中，并封闭在大小为（w/4， w/16） 的盒子中
- 椭圆是旋转角度度数
- 椭圆在 0 到 360 度之间延伸一条弧线
- 图形的颜色将是 （ 255， 0， 0 ），表示 BGR 值中的蓝色。
- 椭圆的厚度为 2。

MyFilledCircle（圆）

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)

与椭圆函数类似，我们可以观察到 circle 接收为参数：
- 将显示圆圈的图像（img)
- 圆的中心表示为点中心
- 圆的半径：w/32
- 圆圈的颜色：（ 0， 0， 255 ） 在 BGR 中表示红色
- 由于厚度 = -1，因此圆将被绘制填充。

MyPolygon

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)

为了绘制一个填充的多边形，我们使用函数 fillPoly（） 。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

矩形

 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:

# 2.b. Creating rectangles
cv.rectangle(rook_image,
 (0, 7 * W // 8),
 (W, W),
 (0, 255, 255),
 -1,
 8)

最后，我们有了cv::rectangle函数（我们没有为这个家伙创建一个特殊函数）。我们注意到：
- 矩形将绘制在rook_image
- 矩形的两个相对顶点由 （ 0， 7*w/8 ） 和 （ w， w ） 定义
- 矩形的颜色由 （ 0， 255， 255 ） 给出，它是黄色的 BGR 值
- 由于厚度值由 FILLED （-1） 给出，因此矩形将被填充。