OpenCV Can't find large rectangle contour

1. How do you find the biggest contour in OpenCV?
2. How do you find a rectangle in OpenCV?
3. How do you expand contour in OpenCV?
4. How does OpenCV detect contour?

How do you find the biggest contour in OpenCV?

OpenCV is very dynamic in which we can first find all the objects (or contours) in an image using the cv2. findContours() function. We can then find the size of each object using the cv2. contourArea() function.

How do you find a rectangle in OpenCV?

Find the approximate contour for each of the contours. If the number of vertex points in the approximate contour is 4 then we compute the aspect ratio to make a difference between the rectangle and square. If the aspect ratio is between 0.9 and 1.1 we say it is a square else a rectangle See the below pseudocode.

How do you expand contour in OpenCV?

You can use cv::dilate() and cv::erode() then detect the contours again.

How does OpenCV detect contour?

Use the findContours() function to detect the contours in the image. Draw Contours on the Original RGB Image.