rotate and resize the image view with single finger in android

Question

I am developing an app which has feature that resizing and rotating the imageview by dragging its bottom right corner button.

I saw one app which has feature that if

Answer 1

I'm assuming the rotation/scaling happens from the image center? In that case, it's simple trigonometry to find the rotation angle and the size:

Calculate dx and dy of the finger's coordinates minus the center coordinates. Math.atan2(dy, dx) is the rotation angle (in radians) and Math.hypot(dx,dy) can be used for the relative size, or just double the dx/dy and use directly.