Using Masks and Layers—Painting, Filling, and Color Tools - GIMP 2.6 for Photographers: Image Editing with Open Source Software - page 266

You've almost finished with the front of the monitor. What's missing?
Most monitors have control knobs or buttons of some sort, so why not create
a couple of knobs as separate image objects on a new layer, of course.
• Create a layer titled knob on the top of the stack in the Layers dialog.
Zoom into the left bottom corner of the image. Use the Ellipse Select tool
to create an ellipse. Fill the ellipse with a gradient blend so the top is
white and the bottom black.
• Use the Move tool to move the elliptic selection slightly horizontally. Pay
attention to the tool options: Move > Selection .
• Access the color area and select a light silvery gray as the foreground
color. Use the Edit > Fill with FG Color menu item to fill the selection. If you
like, add a bevel to the selected front of the knob ( Filters > Decor > Add
Bevel ). Voila! You're done with the first knob. Don't forget to delete the
selection ( Select > None ).
• Now duplicate the knob layer (by clicking the Duplicate Layer button in
the Layers dialog) and paste it on the right bottom corner. Scale the new
layer to about 70% of its size to make it proportionately smaller.
• The front of the monitor is done. Save your image.
Figure 3.81
Using an elliptic
selection with a
gradient fill to create a
control knob