To identify circles, ellipses or in general any shape in which the pixels are connected we use the
SimpleBlobDetector() function of OpenCV. In non-technical terms, a blob is understood as a thick liquid drop. Here, we are going to call all shapes as a blob. Our task is to detect and recognize whether the blob is a circle or not.
OpenCV provides a convenient way to detect blobs and filter them based on different characteristics. There are various different parameters that control the identification process and the results. The important parameters used for this project are:
- Filter by Area – This is to avoid any identification of any small dots present in the image that can be wrongly detected as a circle.
- Filter by Circularity – This helps us to identify, shapes that are more similar to a circle.
Circularity = .
A true circle has circularity of 1, a square has a circularity near 78%.
- Filter by Convexity – Concavity in general, destroys the circularity.More is the convexity, the closer it is to a close circle.
- Filter by Inertia – Objecs similar to a circle has larger inertial.E.g. for a circle, this value is 1, for an ellipse it is between 0 and 1, and for a line it is 0. To filter by inertia ratio, set filterByInertia = 1, and set, 0 <= minInertiaRatio <= 1 and maxInertiaRatio (<=1 ) appropriately.
Below is the code for identifying Circles:
- Image Translation using OpenCV | Python
- Image Steganography using OpenCV in Python
- Image Processing without OpenCV | Python
- Image Registration using OpenCV | Python
- Image Resizing using OpenCV | Python
- Python | Image blurring using OpenCV
- Image Pyramid using OpenCV | Python
- Reading an image in OpenCV using Python
- Cartooning an Image using OpenCV - Python
- Log transformation of an image using Python and OpenCV
- Python | Detect Polygons in an Image using OpenCV
- Python | Detect corner of an image using OpenCV
- OpenCV Python Program to blur an image
- Negative transformation of an image using Python and OpenCV
- Python | OpenCV program to read and save an Image
- Set Countdown timer to Capture Image using Python-OpenCV
- OpenCV Python Program to analyze an image using Histogram
- Create Local Binary Pattern of an image using OpenCV-Python
- Python Program to detect the edges of an image using OpenCV | Sobel edge detection method
- Python Bokeh - Plotting Ellipses on a Graph
If you like GeeksforGeeks and would like to contribute, you can also write an article using contribute.geeksforgeeks.org or mail your article to firstname.lastname@example.org. See your article appearing on the GeeksforGeeks main page and help other Geeks.
Please Improve this article if you find anything incorrect by clicking on the "Improve Article" button below.