How do you check if a point is inside a polygon OpenCV?

To determine if a point is inside, outside, or on the edge of a shape you can check if the point is within a contour using cv2. pointPolygonTest() . The function returns +1 , -1 , or 0 to indicate if a point is inside, outside, or on the contour, respectively.

How do you draw a polygon in OpenCV?

Step 1: Import cv2 and numpy. Step 2: Define the endpoints. Step 3: Define the image using zeros. Step 4: Draw the polygon using the fillpoly() function.

Is point inside a contour?

To determine if a point is inside, outside, or on the edge of a shape you can check if the point is within a contour using cv2. pointPolygonTest() . Assuming we already have the contour of the shape, we can simply pass the contour and the (x,y) point to the function.

Is point inside a polygon C++?

1) Draw a horizontal line to the right of each point and extend it to infinity 1) Count the number of times the line intersects with polygon edges. 2) A point is inside the polygon if either count of intersections is odd or point lies on an edge of polygon. If none of the conditions is true, then point lies outside.

Where is the biggest 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.

Is a point inside a convex polygon?

A convex polygon is a simple polygon (with no self intersections) such that any line segment between two points inside of the polygon lies completely inside of it. The point will be inside a convex polygon if and only if it lies on the same side of the support line of each of the segments.

What is point in polygon in GIS?

GIS Dictionary. P. point-in-polygon overlay. [spatial analysis] A spatial operation in which points from one feature dataset are overlaid on the polygons of another to determine which points are contained within the polygons.

How do you find a point in a polygon?

What is pointpolygontest and convexity defects?

In this article we will deal with PointPolygonTest and Convexity Defects. This function finds the shortest distance between a point in the image and a contour. It returns the distance which is negative when point is outside the contour, positive when point is inside and zero if point is on the contour.

How to use vector as input to pointpolygontest?

So, this means that you can use std::vector >as InputArrayand so as input to the function pointPolygonTest. Here’s simple example of using pointPolygonTest(of course in new version):

Where can I find more information about the CV2 API?

You may check out the related API usage on the sidebar. You may also want to check out all available functions/classes of the module cv2 , or try the search function .