Opacity of multiple layers

Opacity of multiple layers

Post by -wisegu » Tue, 19 Mar 2002 11:13:25


I noticed recently that GIMP only seems to track the opacity of one layer at
a time.  If I lower the opacity of a layer that contains only one object,
then switch to a different active layer and lower it's opacity, then go back
to the previous layer, that layer shows 100% even though it has obviously
been lowered in value.  Only the most recently edited layer shows the correct
opacity value.

This is problematic if I need to increase the opacity of a layer that I
previously lowered.

Is this behavior to product specification, or does it reflect a bug in the

platform: Solaris 7 SPARC multi-processor
compiled with GCC 2.95.2 and GLIB/GTK 1.2.8.



1. Layer opacity determined by 3rd layer ?

Is it possible to do something equivalent to this:
- Have a background layer
- Have a layer on top of it with whatever blend mode you want
- Have the layer opacity determined not by a fixed %, but by a third image
or layer. For instance if the corresponding pixel of that 3rd image is
black, then the opacity is 0%, if it's white then the opacity is 100%. And
with color images, just separate the channels.

Why do I ask this ? Because on the Lord of the Ring additional DVD
documentary, they explain it's how they did the effect for when the Ring is
'on', using a flame as the 3rd controlling layer.
Guillaume Dargaud
Colorado State University - Dept of Atmospheric Science
  "A bus station is where a bus stops. A train station is where a train
stops. On my desk I have a workstation..."

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