CANVAS:clear_rect(x1, y1, x2, y2)
Make transparent a rectangle defined by the bounding area of
x1,y2 to x2,y2.
Parameters:
x1 The x position of the first corner
y1 The y position of the first corner
x2 The x position of the second corner
y2 The y position of the second corner
-- 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