"Add Layer Mask" adds a mask to the layer, bringing up a dialog in which
you can set the initial properties of the mask. If the layer already has a
layer mask, or cannot have one because it lacks an alpha channel, the menu
entry is insensitive. See the
Layer Mask
section for more information.
10.26.1.
Activate Dialog
This command can be accessed from an image menubar as
Layer → Mask → Add Layer Mask
or from the pop-menu you get by right clicking on the active layer
in the Layer Dialog.
10.26.2.
Add Layer Mask dialog
Figure 10.73.
The "Add Layer Mask" dialog
Initialize Layer Mask to
The popup dialog allows you six choices for the initial contents
of the layer mask:
White (full opacity)
This option will produce full opacity when the layer mask;
that is, it will be as if there were no layer mask.
Black (full transparency)
This option will produce complete transparency, so that you
will need to paint on the layer mask in order to make any
part of the layer visible.
Layer's alpha channel
This option will cause the layer mask to produce the same
transparency that is produced by the layer's alpha channel.
Note that the alpha channel itself will not be altered, so
for partially transparent areas, the transparency will be
"squared", as it were.
Transfer layer's alpha channel
This option does the same thing as the previous option,
except that it also resets the layer's alpha channel to full
opacity. The effect, then, is to transfer the transparency
information from the alpha channel to the layer mask,
leaving the layer with the same appearance as before.
Selection
This option converts the selection into a layer mask, so
that selected areas are opaque, and unselected areas are
transparent. If any areas are partially selected, toggling
the QuickMask
button
will help you predict what the effects are going to be.
Grayscale copy of layer
This option converts the layer itself into a layer mask. It
is mainly useful when you plan to add new contents to the
layer afterwards.
Invert Mask
If you check "Invert Mask" at the bottom of the dialog, then the
resulting mask is inverted, so that transparent becomes opaque and
vice versa.
When you click on "OK" the mask symbol appears at the right of the layer
thumbnail in the Layer Dialog.
