Working with masks : Editing masks
 
Editing masks
When you edit a mask, you change either its area or the degree of masking. For example, painting over an object to mask it changes the area, whereas applying a gradient fill changes the degree of masking.
You can invert the transparency of a mask, so that black pixels become white, white pixels become black, and shades of gray become their mirror value, which is the maximum value (255) minus the current value.
You can use a gradient, pattern, or texture mask to create interesting effects. A gradient mask varies the opacity of an image from fully hidden to fully transparent by fading the image in or out. A pattern or texture mask varies the image opacity in a repeated pattern throughout the image.
Using a gradient mask
Using a pattern mask
You can edit the layer properties of a mask, such as the name, visibility, or opacity. For more information, see Working with layers.
To invert a mask
Edit tab 
1 On the Layers palette, click a mask layer.
2 Choose Layers Invert Mask/Adjustment.
To create a gradient, pattern, or texture mask
Edit tab 
1 Create a new mask.
2 Click the Highlight mask area button on the Layers palette to display the mask overlay.
3 On the Tools toolbar, click the Flood Fill tool .
If you want to fill all pixels in the mask, set the Match mode control on the Tool Options palette to None.
4 On the Materials palette, choose a gradient, texture, or pattern.
5 Click the mask to apply the foreground material; right-click the mask to apply the background material.
For information about creating masks, see Creating masks.
For information about gradients, patterns, or textures, see Using gradients, Using patterns, or Using textures.