I placed a canvas in the screen and added a Sprite Type. I used the new sprite type to place one in the top left and one in the bottom right. I then get the position of the sprite which will aid in calculating the size.
Of course you will choose a sprite image that is less obvious that what I used but I needed to see them in the screen.
[Edit]
After giving it some thoughts, you don’t need the sprite in the top left corner because it is (0,0) so the only sprite you will need is the bottom-right corner which is approx. (290, 440)