Add this to your Home Screen (Share › Add to Home Screen) so your diary is kept for good.
No paintings yet. Add the one on your easel.
No size needed: the proportions are measured from your first photo, when you drag the corners. Every later session is straightened to the same shape, so they line up.
No sessions yet. Photograph the canvas as it stands today.
Drag each corner onto the canvas's corner. The loupe shows where you are.