OpenCV学习笔记 - task04

第五章: OpenCV实现图形的绘制

画线:

line(img, 开始点, 结束点, 颜色[, ...])
# params: 
# img: 在哪个图像上画线
# 开始点, 结束点: 指定线的开始与结束位置
# 颜色, 线宽, 线型
# Shift: 坐标缩放比例

代码:

import cv2 
import numpy as np 
import pandas as pd 


# cv2.namedWindow()


img = np.zeros((480, 640, 3), np.uint8)



# 画线, 坐标点为(x, y)
cv2.line(img, (50, 50), (300, 400), (0, 0, 255))

cv2.imshow('draw', img) 

cv2.waitKey(0) 

cv2.destroyAllWindows() 

效果:

代码 - 加线宽:

import cv2 
import numpy as np 
import pandas as pd 


# cv2.namedWindow()


img = np.zeros((480, 640, 3), np.uint8)



# 画线, 坐标点为(x, y)
cv2.line(img, (50, 50), (300, 400), (0, 0, 255), 5)

cv2.imshow('draw', img) 

cv2.waitKey(0) 

cv2.destroyAllWindows() 

效果:

代码 - 加线型:

import cv2 
import numpy as np 
import pandas as pd 


# cv2.namedWindow()


img = np.zeros((480, 640, 3), np.uint8)



# 画线, 坐标点为(x, y)
# 默认是8, 设置为4, 有锯齿
cv2.line(img, (50, 50), (300, 400), (0, 0, 255), 2, 4)

cv2.imshow('draw', img) 

cv2.waitKey(0) 

cv2.destroyAllWindows() 

效果:

可以查看相关源码进行学习补充:

CV_EXPORTS_W void line(InputOutputArray img, Point pt1, Point pt2, const Scalar& color,
                     int thickness = 1, int lineType = LINE_8, int shift = 0);


enum LineTypes {
    FILLED  = -1,
    LINE_4  = 4, //!< 4-connected line
    LINE_8  = 8, //!< 8-connected line
    LINE_AA = 16 //!< antialiased line
};

画矩形:

import cv2 
import numpy as np 
import pandas as pd 


# cv2.namedWindow()


img = np.zeros((480, 640, 3), np.uint8)



# # 画线, 坐标点为(x, y)
# cv2.line(img, (50, 50), (300, 400), (0, 0, 255), 2, 4)

# 画矩形
cv2.rectangle(img, (10, 10), (100, 100), (0, 0, 255), -1)
# 左上角, 右下角, 颜色RGB

cv2.imshow('draw', img) 

cv2.waitKey(0) 

cv2.destroyAllWindows() 

效果:

画圆:

import cv2 
import numpy as np 
import pandas as pd 


# cv2.namedWindow()


img = np.zeros((480, 640, 3), np.uint8)



# # 画线, 坐标点为(x, y)
# cv2.line(img, (50, 50), (300, 400), (0, 0, 255), 2, 4)

# # 画矩形
# cv2.rectangle(img, (10, 10), (100, 100), (0, 0, 255), -1)

# 画圆
cv2.circle(img, (320, 240), 100, (0, 0, 255))
cv2.circle(img, (320, 240), 5, (0, 0, 255), -1)
# img, 圆心坐标, 半径, 颜色

cv2.imshow('draw', img) 

cv2.waitKey(0) 

cv2.destroyAllWindows() 

效果:

画椭圆:

ellipse(img, 中心点, 长宽的一半, 角度, 从哪个角度开始, 到哪个角度结束[, ...])

import cv2 
import numpy as np 
import pandas as pd 


# cv2.namedWindow()


img = np.zeros((480, 640, 3), np.uint8)



# # 画线, 坐标点为(x, y)
# cv2.line(img, (50, 50), (300, 400), (0, 0, 255), 2, 4)

# # 画矩形
# cv2.rectangle(img, (10, 10), (100, 100), (0, 0, 255), -1)

# # 画圆
# cv2.circle(img, (320, 240), 100, (0, 0, 255))
# cv2.circle(img, (320, 240), 5, (0, 0, 255), -1)
# # img, 圆心坐标, 半径, 颜色

# 绘制椭圆
cv2.ellipse(img, (200, 200), (100, 80), 0, 0, 360, (0, 0, 255))

cv2.imshow('draw', img) 

cv2.waitKey(0) 

cv2.destroyAllWindows() 

注意:

• 度是按顺时针计算的
• 0度是从左侧开始的
• 第一个角度是长方形的角度, 也是顺时针转动

当添加-1 的时候, 绘制扇形:

cv2.ellipse(img, (200, 200), (100, 80), 0, 0, 270, (0, 0, 255), -1)

效果: