Mask objects using the Layers panel
The quickest way to add an empty, transparent bitmap mask
is through the Layers panel. The Layers panel adds a white mask
to an object, which you can customize by drawing on it with the
bitmap tools.
Select the object you want to mask.
At the bottom of the Layers panel, click the Add Mask button.
Fireworks
applies an empty mask to the selected object. The Layers panel displays
a mask thumbnail representing the empty mask.
(Optional) If the masked object is a bitmap, use one of the
marquee or lasso tools to create a pixel selection.
From the Tools panel, select a bitmap painting tool.
Set tool options in the Property inspector.
With the mask still selected, draw on the empty mask. In
the areas where you draw, the underlying masked object is hidden.
Image with mask applied
The mask as it appears in the Layers panel
PDF (adobe.com)
