CANVAS:clear_rect

    CANVAS:clear_rect(x1, y1, x2, y2)

Make transparent a rectangle defined by the bounding area of x1,y2 to x2,y2.

Parameters

Parameter	Type	Description
x1	#number	The x position of the first corner
y1	#number	The y position of the first corner
x2	#number	The x position of the second corner
y2	#number	The y position of the second corner

Example

    -- Fill a canvas with red and poke a transparent hole in the middle of it
    function MakeTransparentHole(name)
        local canvas = gre.get_canvas(name)
        local size = canvas:get_dimensions()
        local hole_width = size.width / 3
        local hole_height = size.height / 3

        cavans:fill(0xff0000)
        canvas:clear_rect(hole_width, hole_height, 2*hole_width, 2*hole_height)
    end