Facemesh/FaceExtension help - stroke detecting app

I am trying to make a stroke detecting app using the face extension, but I have ran into some problems. I am currently doing the F.A.S.T method to detect a stroke, and using facemesh to do a blowing test. I'm using the points 17,14,78,308, which are top, bottom, left, and right of the mouth. They don't follow the mouth exactly when I am doing these movements. Any help?

Also, a problem I have encountered with the face extension and extensions in general is that if ui change is made or if you change to the page with the extension(ie. not starting in the extension page), the canvas will be blank. Why is this?


This is my code so far with the mouthareaL and mouthareaR being my formulas

You may need to show us more of what you are doing, advise on which extension, and expand upon your calculation procedures.