Edge detection

import cv2
from matplotlib import pyplot as plt
 
def showimage(myimage, figsize=[10,10]):
    if (myimage.ndim>2):  #This only applies to RGB or RGBA images (e.g. not to Black and White images)
        myimage = myimage[:,:,::-1] #OpenCV follows BGR order, while matplotlib likely follows RGB order
 
    fig, ax = plt.subplots(figsize=figsize)
    ax.imshow(myimage, cmap = 'gray', interpolation = 'bicubic')
    plt.xticks([]), plt.yticks([])  # to hide tick values on X and Y axis
    plt.show()
 
image=cv2.imread('carre-03.jpg')
showimage(image)
 
gray=cv2.cvtColor(image,cv2.COLOR_BGR2GRAY)
 
edged=cv2.Canny(gray,30,200)
showimage(edged)
 
_, contours, hierarchy=cv2.findContours(edged,cv2.RETR_EXTERNAL,cv2.CHAIN_APPROX_NONE)
 
# print(contours)
# print('Numbers of contours found=' + str(len(contours)))
 
#use -1 as the 3rd parameter to draw all the contours
cv2.drawContours(image,contours,-1,(0,255,0),3)
showimage(image)