案例-使用python实现基于opencv的形状识别

该案例主要涉及到不同形状的图形。根据获得轮廓，计算边数。来判断属于什么形状，并将之输出在图片上。具体代码和结果如下：

import cv2
from urllib3 import connection_from_url
img = cv2.imread("pyopencv_again/shape.jpg")
imgconts = img.copy()
img = cv2.cvtColor(img,cv2.COLOR_BGR2GRAY)
canny = cv2.Canny(img,150,200)
conts,_ = cv2.findContours(canny,cv2.RETR_EXTERNAL,cv2.CHAIN_APPROX_NONE)


for cont in conts:
    #print(cont)
    cv2.drawContours(imgconts,cont,-1,(255,0,0),2)
    area = cv2.contourArea(cont)
    if area >500:
        #计算周长作为精度参数
        peri = cv2.arcLength(cont,True)
        #多边形逼近轮廓  获得边
        vertices = cv2.approxPolyDP(cont,peri*0.02,True)
        #统计每个形状的边数
        contsnum = len(vertices)
        #最大外接矩形 获取（x,y）宽和高
        x,y,w,h = cv2.boundingRect(vertices)
        
        if contsnum ==3:
            cv2.putText(imgconts,'3',(x,y-5),cv2.FONT_HERSHEY_SIMPLEX,1,(0,0,255),1)
            cv2.rectangle(imgconts,(x,y),(x+w,y+h),(0,255,0),2)
        if contsnum ==4:
            cv2.putText(imgconts,'4',(x,y-5),cv2.FONT_HERSHEY_SIMPLEX,1,(0,0,255),1)
            cv2.rectangle(imgconts,(x,y),(x+w,y+h),(124,25,110),2)
        if contsnum == 5:
            cv2.putText(imgconts,'5',(x,y-5),cv2.FONT_HERSHEY_SIMPLEX,1,(0,0,255),1)
            cv2.rectangle(imgconts,(x,y),(x+w,y+h),(1,115,110),2)
        if contsnum >= 6:
            cv2.putText(imgconts,'circle',(x,y-5),cv2.FONT_HERSHEY_SIMPLEX,1,(0,0,255),1)
            cv2.rectangle(imgconts,(x,y),(x+w,y+h),(101,15,10),2)


#cv2.imshow('img',img)
cv2.imshow('imgcont',imgconts)
cv2.waitKey()