When you first pick up a brush, Matte becomes the default mode.
`In Matte mode, areeyuz matching the current background color are transparent.
In Matte mode, areas matching the current background color are transparent.
`Replace mode is like Matte mode, except that no colors are transparent.
Replc mode is like Matte mode, except that no colors are transparent.
The entire rectangular area that was originally picked up becomes visible.