opencv-python 图像处理 —— 直线与圆检测

你的名字 2022-01-21 05:21 501阅读 0赞

## 直线检测，使用HoughLines和HoughLinesP函数完成 ##

cv2.HoughLineP()的参数为

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dqaDI2MjIwNzUxMjc_size_16_color_FFFFFF_t_70]

代码实例

import cv2
    import numpy as np
    
    img = cv2.imread('line-cycle.png')
    gray = cv2.cvtColor(img, cv2.COLOR_BGR2GRAY)
    edges = cv2.Canny(gray, 50, 120)
    minLineLength = 20 # 最小直线长度，太小舍去
    maxLineGap = 5 # 最大线段间隙， 太大舍去
    lines = cv2.HoughLinesP( # P意味着概率，所谓“概率版本的Hough变换”
        edges, 1, np.pi/180, 100, minLineLength, maxLineGap
    )
    for each in lines[0: 10]: # 绘制直线，十条
        for x1, y1, x2, y2 in each:
            cv2.line(img, (x1, y1), (x2, y2), (255, 0, 0), 2)
    
    cv2.imwrite('line-cycle-detect.jpg', img)
    cv2.imshow('edges', edges)
    cv2.imshow('lines', img)
    cv2.waitKey()
    cv2.destroyAllWindows()

如图所示为直线检测图。用蓝色的线条绘制出了十条检测出来的直线。这是书上的例子。  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dqaDI2MjIwNzUxMjc_size_16_color_FFFFFF_t_70 1]  
检测一个单纯一点的图，包含一条直线和一个圆。如图为将直线用蓝色的线条替代。  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dqaDI2MjIwNzUxMjc_size_16_color_FFFFFF_t_70 2]

## 圆检测 ##

绘制圆和圆心  
代码

import cv2
    import numpy as np
    
    planets = cv2.imread('planet_glow.jpg')
    gray_img = cv2.cvtColor(planets, cv2.COLOR_BGR2GRAY)
    img = cv2.medianBlur(gray_img, 5)
    cimg = cv2.cvtColor(img,cv2.COLOR_GRAY2BGR)
    
    circles = cv2.HoughCircles(img,cv2.HOUGH_GRADIENT,1,120,
                                param1=100,param2=30,minRadius=0,maxRadius=0)
    
    circles = np.uint16(np.around(circles))
    
    for i in circles[0,:]:
        # draw the outer circle
        cv2.circle(planets,(i[0],i[1]),i[2],(0,255,0),2)
        # draw the center of the circle
        cv2.circle(planets,(i[0],i[1]),2,(0,0,255),3)
    
    cv2.imwrite("planets_circles.jpg", planets)
    cv2.imshow("HoughCirlces", planets)
    cv2.waitKey()
    cv2.destroyAllWindows()

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dqaDI2MjIwNzUxMjc_size_16_color_FFFFFF_t_70 3]  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dqaDI2MjIwNzUxMjc_size_16_color_FFFFFF_t_70 4]

**参考**  
《opencv3 计算机视觉: python语言实现》

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