How to find number of contours in OpenCV Python

You can find the total number of contours in OpenCV Python with the following steps.

  • Install the OpenCV
  • Import the OpenCV
  • Read the Image
  • Convert the Image into GrayScale
  • Convert the Grayscale Image into a Black and White Image
  • Find the Contours using the function
  • Draw the Contours (Optional)
  • Find Number of Contours
  • Display Output Image with Contours (Optional)

Step 1

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

pip install opencv-python

Find the number of Contours in OpenCV

# Import the required libraries
import cv2 
import numpy as np

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

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

# Number of Contours
total_contours = len(contours)

# Display the Original Image and Output
cv2.imshow('Original Image',image)
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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