Building a simple program with OpenCV

There are many program samples that show how to use OpenCV using Python. In our case, we build a simple program to detect a circle in a still image.

Consider we have the following image, which is used for testing. You can find the image file in the source code files, called circle.png.

To find a circle in a still image, we use circle Hough Transform (CHT). A circle can be defined as follows:

(a,b) is the center of a circle with radius r. These parameters will be computed using the CHT method.

Let's build a demo!

We will build a program to read an image file. Then, we will detect a circle form in an image using the cv2.HoughCircles() function.

Let's start to write these scripts:

import cv2
import numpy as np


print('load image')
orig = cv2.imread('circle.png')
processed = cv2.imread('circle.png', 0)
processed = cv2.medianBlur(processed, 19)

print('processing...')
circles = cv2.HoughCircles(processed, cv2.HOUGH_GRADIENT, 1, 70,
              param1=30,
  ...