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17.Rectangular circle drawing

1. Drawing of rectangle

rectangle（img，pt1，pt2，color，thickness=None，lineType=None，shift=None）

Parameter Description:

img: canvas or carrier image.

pt1, pt2: required parameters. The vertices of the rectangle represent the vertex and the diagonal vertex respectively, that is, the upper left corner and the lower right corner of the rectangle (these two vertices can determine a unique rectangle)

color: required parameter. Used to set the color of the rectangle

thickness: optional parameter. Used to set the width of the rectangle side. When the value is a negative number, it means the rectangle is filled.

lineType: optional parameter. Used to set the type of line segment, optional 8 (8 adjacent connecting lines - default), 4 (4 adjacent connecting lines) and cv2.LINE_AA is anti-aliasing

2. Drawing of circles

cv2.circle(img, center, radius, color[,thickness[,lineType]])

Parameter Description:

img: canvas or carrier image

center: is the coordinate of the center of the circle, format: (50,50)

radius: radius

color: color

thickness: Line thickness. Defaults to 1. If -1, fill solid.

lineType: line type. The default is 8, connection type. The following table explains

3. Draw ellipse

cv2.ellipse(img, center, axes, angle, StartAngle, endAngle, color[,thickness[,lineType]])

center：center point of the ellipse，（x，x）

axes：refers to the short radius and long radius，（x，x）

angle：refers to the angle of counterclockwise rotation

StartAngle：The angle of the starting angle of the arc

endAngle：the angle of the arc’s end angle

For img and color, please refer to the description of the circle.

#The fifth parameter refers to the angle at which the drawing starts counterclockwise, and the sixth parameter refers to the angle at which the drawing ends counterclockwise.

# If the 456 parameter is added with a sign, it represents the opposite direction, that is, clockwise.

4. Draw polygons

cv2.polylines(img,[pts],isClosed, color[,thickness[,lineType]])

pts：vertices of the polygon

isClosed：Whether it is closed.（True/False）

Other parameters refer to the drawing parameters of the circle.

Code path：muto/Samples/OpenCV/03_Image processing and text drawing/05Draw a rectangular circle.ipynb

import cv2
import   numpy as np
newImageInfo   = (500,500,3)
dst =   np.zeros(newImageInfo,np.uint8)
#  1 2 upper left corner 3 lower right corner 4 5 fill -1 >0 line w
cv2.rectangle(dst,(350,100),(400,270),(0,255,0),3)
# 2 center   3 r
cv2.circle(dst,(250,250),(50),(255,0,0),2)
# 2 center   3 axis 4 angle 5 begin 6 end 7
cv2.ellipse(dst,   (256,256), (150,100), 0, 0, 180, (0,255,255), -1)
points =   np.array([[150,50], [140,140], [200,170], [250,250], [150,50]], np.int32)
#print(points.shape)
points =   points.reshape((-1,1,2))
#print(points.shape)
cv2.polylines(dst,[points],True,(255,255,0))
#   cv2.imshow('dst',dst)
    # cv2.waitKey(0)

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import   matplotlib.pyplot as plt
dst =   cv2.cvtColor(dst, cv2.COLOR_BGR2RGB)
plt.imshow(dst)
plt.show()