图像轮廓

图像轮廓

import cv2 as cv
import numpy as np
import matplotlib.pyplot as plt

def display_img(img):
    cv.imshow('image',img)
    cv.waitKey(0)
    cv.destroyAllWindows()


def operate_img(file):
    img = cv.imread(file)#imread(file,cv.IMREAD_GRAYSCALE)
    gray = cv.cvtColor(img,cv.COLOR_BGR2GRAY)
    ret,thresh = cv.threshold(gray,127,255,cv.THRESH_BINARY)
    #display_img(thresh)
    contours,hierachy = cv.findContours(thresh,cv.RETR_TREE,cv.CHAIN_APPROX_NONE)
    con_img = img.copy()
    res = cv.drawContours(con_img,contours,-1,(0,255,5),2)
    display_img(res)
    cors= contours[0]
    area = cv.contourArea(cors)
    line_len = cv.arcLength(cors,True)
    print (area,line_len )
   
    
operate_img(file="gui.jpeg")

轮廓近似

def operate_img(file):
    img = cv.imread(file)#imread(file,cv.IMREAD_GRAYSCALE)
    gray = cv.cvtColor(img,cv.COLOR_BGR2GRAY)
    ret,thresh = cv.threshold(gray,127,255,cv.THRESH_BINARY)
    #display_img(thresh)
    contours,hierachy = cv.findContours(thresh,cv.RETR_TREE,cv.CHAIN_APPROX_NONE)
    
    cors= contours[-1]
    area = cv.contourArea(cors)
    line_len = cv.arcLength(cors,True)
    print (area,line_len )

    epsilon  = 0.01*line_len
    approx = cv.approxPolyDP(cors,epsilon,True)
    con_img = img.copy()
    res = cv.drawContours(con_img,[approx],-1,(0,255,5),2)
    display_img(res)

矩形近似

def jvxing_img(file):
    img = cv.imread(file)#imread(file,cv.IMREAD_GRAYSCALE)
    gray = cv.cvtColor(img,cv.COLOR_BGR2GRAY)
    ret,thresh = cv.threshold(gray,127,255,cv.THRESH_BINARY)
    #display_img(thresh)
    contours,hierachy = cv.findContours(thresh,cv.RETR_TREE,cv.CHAIN_APPROX_NONE)
    cors= contours[-1] 
    area = cv.contourArea(cors)
    x,y,w,h = cv.boundingRect(cors)
    rect_area = w*h
    extent = float(area)/rect_area
    print ("轮廓面积与边界面积比例",extent)

    x,y,w,h = cv.boundingRect(cors)
    img = cv.rectangle(img,(x,y),(x+w,y+h),(0,255,9),2)
    display_img(img)

圆形近似

def circle_img(file):
    img = cv.imread(file)#imread(file,cv.IMREAD_GRAYSCALE)
    gray = cv.cvtColor(img,cv.COLOR_BGR2GRAY)
    ret,thresh = cv.threshold(gray,127,255,cv.THRESH_BINARY)
    #display_img(thresh)
    contours,hierachy = cv.findContours(thresh,cv.RETR_TREE,cv.CHAIN_APPROX_NONE)
    cors= contours[-1]
    (x,y),r= cv.minEnclosingCircle(cors)
    center = (int(x),int(y))
    r = int(r)
    img = cv.circle(img,center,r,(0,255,9),2)
    display_img(img)