Quoting bob <for...@gimpusers.com>:
> I'm working through a tutorial made by photoshop:
> Step 24 is interesting. Water spray is seperated from a background colour,
> using a manipulation of channels.
> I can't seem to figure out how to the same thing in gimp.
> Any idea how I can do it?
The process is fairly similar for GIMP.
1. Open your Channels Dialog ("Windows->Dockable Dialogs->Channels")
2. Click and release once on the thumbnail preview of the color
channel which offers the highest contrast. (see Note below)
3. Hold down the mouse button (while over the preview thumbnail), drag
the channel to the window in the lower part of the dialog, and release
the mouse button.
4. Click on the red, square button at the bottom of the dialog to turn
the recently dropped channel into a selection.
5. Go back to your Layers Dialog and continue with the tutorial.
Note: The Step #2 is necessary because clicking on the thumbnail
toggles whether the channel is active (highlighted). In this case, the
first click (in Step #2) disables the channel; while the second click
(in Step #3) re-enables it. Basically, you just want to ensure that
all your channels are active (highlighted) after doing your drag-n-drop.
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