shape-recognition

I am working on a shape recognition app. At this moment a set of points (x,y) is determined by corner detector (red points, img. 2 .). Four of these points (in red frames, img. 2 .) are vertices of a rectangle (sometimes a little deformed rectangle). What would be the best way to find them among others? Here is an example of an input image: And it looks like this after corner detection: This is not an answer to your question - it's just suggestion. In my opinion corner detector is a bad way to detect rectangles - it will take much time to calculate all point distances as mathematician1975

I have this practice project that allows the user to draw on the screen as they touch with their fingers. Very simple App I did as exercise way back. My little cousin took the liberty of drawing things with his finger with my iPad on this App (Kids drawings: circle, lines, etc, whatever came to his mind). Then he started to draw circles and then he asked me to make it "good circle" (from my understanding: make the drawn circle perfectly round, as we know no matter how stable we try to draw something with our finger on the screen, a circle is never really as rounded like a circle should be). So

I need the ability to verify that a user has drawn a shape correctly, starting with simple shapes like circle, triangle and more advanced shapes like the letter A. I need to be able to calculate correctness in real time, for example if the user is supposed to draw a circle but is drawing a rectangle, my hope is to be able to detect that while the drawing takes place. There are a few different approaches to shape recognition, unfortunately I don't have the experience or time to try them all and see what works. Which approach would you recommend for this specific task? Your help is appreciated.