How to count objects on an image with Python

In this tutorial, you will learn how you can count the number of objects on an image with Python using CV2.

This is our test image:

Let's jump to the code:

First we need to import our dependencies:

import cv2
import numpy as np

First we need to read our image:

img = cv2.imread('test.jpg')

then we will be converting it into grayscale

img = cv2.cvtColor(img, cv2.COLOR_BGR2GRAY)

after that, we doing thresholding on image

_, thresh = cv2.threshold(img, 225, 255, cv2.THRESH_BINARY_INV)
kernal = np.ones((2, 2), np.uint8)

then we are doing dilation process, removing black distortion:

dilation = cv2.dilate(thresh, kernal, iterations=2)

next step is finding contour shapes:

contours, hierarchy = cv2.findContours(
    dilation, cv2.RETR_EXTERNAL, cv2.CHAIN_APPROX_SIMPLE)

Then we are getting number of contours (objects found):

objects = str(len(contours))

We can now print number of objects on an image

text = "Obj:"+str(objects)
cv2.putText(dilation, text, (10, 25),  cv2.FONT_HERSHEY_SIMPLEX,
            0.4, (240, 0, 159), 1)

For the lasr step we can show, original, threshold and dilation image:

cv2.imshow('Original', img)
cv2.imshow('Thresh', thresh)
cv2.imshow('Dilation', dilation)

cv2.waitKey(0)
cv2.destroyAllWindows()

This is our final result:

Thank you all.

Comments

[Matt Curcio]

Nice step-by-step explanations.
Good job

[Stokry]

Thanks😀