Figure 16.329. The Alpha to Logo filters menu
These filters correspond to the
logo-generating script-fu scripts.
They add all kinds of special effects to the alpha channel of the active
layer (that is, to the pixels with a non-zero alpha value).
The menu items and the corresponding functions are enabled only if the
active layer has an alpha channel. If you see that the menu items are
grayed out, try to add an alpha
The filter effect will always be applied according to the alpha values.
The alpha of any pixel has a value
ranging from 0 (transparent) to 255 (fully opaque). It is possible to
apply a filter only partially to some (or all) pixels
by using alpha values from 1 to 254.
You will notice that this is similar to
selecting pixels partially.
In fact, internally these filters always create a
selection from the
alpha channel by transferring the alpha values to the channel which
represents the selection, and then work on the selection.
How to apply an “Alpha to Logo” filter to a selection?
If the active layer is the background layer, make sure that an
alpha channel exists, otherwise
add an alpha channel.
If a layer name in the Layer Dialog is in bold, then this layer has
no Alpha channel.
Invert the selection:
Remove the (inverted) selection:
Apply the “Alpha to Logo” filter (the filters ignore the
selection, you don't need to re-invert the selection).