The canvas is the inner area of the window with a lighter background, and is where the images can be placed. The canvas will expand to fit your images.
Canvas > Optimize
Fit the canvas snugly around all the images on the board.
CtrlShiftP/⇧⌘P is Pack all and Optimize in one shortcut!
Adjusts the view so the full canvas is visible.
Canvas > Reset camera
The camera will be reset to the default position (0, 0) in the window.
Canvas > Reset camera zoom
The view zoom will be reset to 100%.
Canvas > Lock canvas
Locks everything on the canvas so items cannot be interacted with. Great when you don't want to accidentally move things around.
Canvas > Grayscale
Turns everything on the canvas into grayscale.
The formula used is
Turn only some images grayscale with Toggle Grayscale