如何在 opencv 中绘制轮廓？

Question

cv2.error: OpenCV(4.6.0) /io/opencv/modules/imgproc/src/contours.cpp:195: error: (-210:Unsupported format or combination of formats) [Start]FindContours supports only CV_8UC1 images when mode != CV_RETR_FLOODFILL otherwise supports CV_32SC1 images only in function 'cvStartFindContours_Impl'

here's my code. whats wrong?

import cv2 
import numpy as np 
image = cv2.imread('j.jpg') 
cv2.waitKey(0) 
gray = cv2.cvtColor(image, cv2.COLOR_BGR2GRAY) 
edged = cv2.Canny(gray, 30, 200) 
cv2.waitKey(0) 
  
contours, hierarchy = cv2.findContours(edged,  
    cv2.RETR_EXTERNAL, cv2.CHAIN_APPROX_NONE) 
  
cv2.imshow('Canny Edges After Contouring', edged) 
cv2.waitKey(0) 
  
print("Number of Contours found = " + str(len(contours))) 
cv2.drawContours(image, contours, -1, (0, 255, 0), 3) 
  
cv2.imshow('Contours', image) 
cv2.waitKey(0) 
cv2.destroyAllWindows() 

i'm trying to countour the lines at the image

Answer 1

I just tried your code in python3 and everything works normal, your code works.

here is the coded I tested, just remove some waitkeys.

import cv2 
            import numpy as np 
            image = cv2.imread('1.png') 

            gray = cv2.cvtColor(image, cv2.COLOR_BGR2GRAY) 
            edged = cv2.Canny(gray, 30, 200) 

              
            contours, hierarchy = cv2.findContours(edged,  
                cv2.RETR_EXTERNAL, cv2.CHAIN_APPROX_NONE) 
              
            cv2.imshow('Canny Edges After Contouring', edged) 

              
            print("Number of Contours found = " + str(len(contours))) 
            cv2.drawContours(image, contours, -1, (0, 0, 255), 3) 
              
            cv2.imshow('Contours', image) 
            cv2.waitKey(0) 
            cv2.destroyAllWindows() 

ALso I changed the image for a jpg image, here are the results. enter image description here

As you can see the countours are drawed in red color.

I have opencv 4.2 version, maybe yours are a bit older.