How is the screenshot on mobile? Which camera is based on front camera or back camera?

What is seen on a phone or computer screen is essentially a canvas that is refreshed over and over again. Different applications occupy each rectangle of that canvas, and give instructions on when and how to draw that rectangle. For example, after knowing that the button has been clicked, it gives instructions to change the image of the button, so that it seems that the button has been pressed. Developers of applications do not have to deliver these “instructions” directly to the canvas. Because that work is a bit complicated. In between there are some intermediate layers through which these instructions are created and finally delivered to the canvas.

At the end of the day, this canvas is a matrix. There are different colors in each room. The matrix itself is encoded as an image when taking a screenshot. So no “camera” is needed.