What does convexityDefects return?
convexityDefects() returns four values which are [ start point, end point, farthest point, approximate distance to farthest point ]. I do not understand how the five lines of for loop is working?
What is convexity Defects OpenCV?
Convexity Defects Any deviation of the object from this hull can be considered as convexity defect. We can visualize it using an image. We draw a line joining start point and end point, then draw a circle at the farthest point. Note.
How do you identify convexity defects?
Convexity Defects We draw a line joining start point and end point, then draw a circle at the farthest point. Remember we have to pass returnPoints = False while finding convex hull, in order to find convexity defects. input contour. the output vector of convexity defects.
What is convexity Defects?
Convex defect. It can be depicted as the calculated difference between the convex hull and the contour. The convexity defect is defined as the points farthest from the convex points. So, if the finger tips are considered as the convex points, the trough between the fingers can also be considered as convexity defects.
What is convex hull in OpenCV?
Hull means the exterior or the shape of the object. Therefore, the Convex Hull of a shape or a group of points is a tight fitting convex boundary around the points or the shape. The Convex Hull of the two shapes in Figure 1 is shown in Figure 2. The Convex Hull of a convex object is simply its boundary.
How do you draw contours in OpenCV Python?
To draw all the contours in an image:
- cv2. drawContours(img, contours, -1, (0,255,0), 3)
- cv2. drawContours(img, contours, 3, (0,255,0), 3)
- cnt = contours[4] cv2. drawContours(img, [cnt], 0, (0,255,0), 3)
What is Convex Hull Opencv?
A Convex object is one with no interior angles greater than 180 degrees. A shape that is not convex is called Non-Convex or Concave. Hull means the exterior or the shape of the object. Therefore, the Convex Hull of a shape or a group of points is a tight fitting convex boundary around the points or the shape.
What is convexity in image processing?
In simple words, convexity defect is a cavity in an object (blob, contour) segmented out from an image. That means an area that do not belong to the object but located inside of its outer boundary -convex hull (read documentation of cv::convexHull function for details).
What is Convex Hull OpenCV?
What is cv2 approxPolyDP?
The process of approximating the shape of a contour of a given polygon to the shape of the original polygon to the specified precision is called approximation of a shape of the contour. We make use of a function in OpenCV called approxPolyDP() function to perform an approximation of a shape of a contour.
Where is the largest contour on OpenCV?
You can start by defining a mask in the range of the red tones of the book you are looking for. Then you can just find the contour with the biggest area and draw the rectangular shape of the book. If you want the book to rotate you can use rect = cv2. minAreaRect(cnt) as you can find it here.
How to find convexity defects of a contour OpenCV?
OpenCV provides a function cv2.convexityDefects () for finding the convexity defects of a contour. This takes as input the contour and its corresponding hull indices and returns an array containing the convexity defects as output. The basic syntax is given below.
Can a convex curve have no convexity defects?
Let’s understand this with the help of the below image. Here, the red line shows the convex hull, the grey line represents the contour and the black arrow shows the deviation of the hull from the contour (convexity defect). So, it’s obvious that the convex curve has no convexity defects.
How is the contour of a convex curve shown?
Here, the red line shows the convex hull, the grey line represents the contour and the black arrow shows the deviation of the hull from the contour (convexity defect). So, it’s obvious that the convex curve has no convexity defects.
Which is the deviation from the convex hull?
Any deviation of the contour from its convex hull is known as the convexity defect. Let’s understand this with the help of the below image. Here, the red line shows the convex hull, the grey line represents the contour and the black arrow shows the deviation of the hull from the contour (convexity defect).