Paint Options
The paint transparency can be set from fully transparent to fully
opaque, which is the default. Move the slider to the left for more
transparent paint, to the right for less transparent.
The brushWidth is 1 pixel wide by default. Move the slider to change
this parameter. The brushWidth will apply to all drawing operations:
line, freehand, rectangle etc.
The snowBrush control sets the density of snow applied with
this paint function. The brushWidth, however, still controls its width.
Since brushWidth is 1 pixel wide by default, this paint function will
look like the freehand function until brushWidth is increased.
(see example below)
