Opencv trapezoid detection

1. How to detect rectangle in OpenCV Python?
2. How to detect circle in OpenCV Python?
3. How to detect a square using OpenCV?

How to detect rectangle in OpenCV Python?

To determine which, we compute the aspect ratio of the shape, which is simply the width of the contour bounding box divided by the height (Lines 23 and 24). If the aspect ratio is ~1.0, then we are examining a square (since all sides have approximately equal length). Otherwise, the shape is a rectangle.

How to detect circle in OpenCV Python?

Syntax. cv2. HoughCircles(image, method, dp, minDist) Where Image is the image file converted to grey scale Method is the algorithm used to detct the circles. Dp is the inverse ratio of the accumulator resolution to the image resolution.

How to detect a square using OpenCV?

Compute the aspect ratio of the contour cnt. Set a range of aspect ratios to detect the square. We set it [0.9, 1.1]. If the ratio is between 0.9 and 1.1, the detected contour is a square else it is a rectangle.