How to find contours in OpenCV Python

You can easily find contours in OpenCV Python with the following steps.

  • Install the OpenCV library
  • Import the OpenCV
  • Read the Image
  • Convert Image into GrayScale
  • Convert Grayscale Image into Black and White
  • Find Contours using function
  • Draw Contours
  • Display Output Image with Contours

Step 1

First, install the OpenCV library if it is not installed using this code.

pip install opencv-python

Find Contours using OpenCV

# Import the required libraries
import cv2 
import numpy as np

# Read the image
img =cv2.imread('shapes.jpg')

# Convert the image into GrayScale
gray_img = cv2.cvtColor(img, cv2.COLOR_BGR2GRAY)

# Convert the Grayscale image into Black and White
_,binary_img = cv2.threshold(gray_img, 100, 255, cv2.THRESH_BINARY)

# Find Contours
contours, hierarchy = cv2.findContours(binary_img, cv2.RETR_EXTERNAL, cv2.CHAIN_APPROX_SIMPLE)

# Draw Contours
drawing = np.zeros((gray_img.shape[0], gray_img.shape[1], 3), dtype=np.uint8)
countours_img = cv2.drawContours(drawing,contours, -1, (255,255,0),3)

# Display the Output
cv2.imshow('Original Image',img)
cv2.imshow('Image with Contours',countours_img )

# Destroy all the windows
Original Image
Image with Contours

I highly recommend you get the “Computer Vision: Models, Learning, and Inference Book” to learn Computer Vision.

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