PhotoPlus X2 User Guide - Serif

148 Layers and Masks
Using masks
Masking in a program like PhotoPlus is a bit more complicated than applying
masking tape to the screen! But fundamentally the concept is the same: you can
hide certain parts of an image—in this case by rendering them transparent, hence
invisible. To do that, you create a mask on a non-Background layer (the
Background layer doesn't support transparency).
By changing the greyscale values on the mask (using the paint tools and other
devices), you can impose corresponding changes in the opacity of the underlying
layer's pixels (values stored as the layer's alpha channel) . For example, by applying
a gradient "blacking out" across the mask, you gradually render the layer's
underlying pixels transparent, and they disappear from the image (see above).
On an adjustment layer, blacking out hides the adjustment's effect. Because you're
working with 256 levels of grey (i.e. opacity), tremendous variations are achievable.
Besides the creative possibilities, ranging from vignetting to multi-layer montage to
gradient-fill masking (see example above) and beyond, a great feature of working
on a mask is that it is "temporary." If you don't like the way things are going, you
can abandon your changes and start over without ever having affected the actual
pixels on the layer!
Each non-Background layer can have one mask at any given time. (The
Background layer can’t have one because it doesn’t support transparency.) Mask
information, like layer information, can only be preserved by saving the image in
the native PhotoPlus (.SPP) format.
The three basic steps in using a mask:
1. Create the mask on a layer.
2. Edit the mask itself to "preview" changes to the layer.
3. Merge the mask with the layer to make the changes permanent, or delete the
mask without applying changes.