Kevin asked for more details about “Ctrl-clicking” layers in Photoshop, so here’s a quickie.
Ctrl-clicking (Command-click for Mac users) a layer allows you to create a selection based on the pixels in that layer. Here’s an example of a multi-layered Photoshop file:
When you ctrl-click Layer 3 (the arrow layer) in the Layer Palette, you create a selection (shown by the dotted lines) based on what the layer contains:
So likewise, ctrl-clicking Layer 2 in the Layer Palette creates a heart-shaped selection:
And similar to many other “selection” functions, if you Shift-Ctrl-Click more than one layer in the Layer Palette, the selections will be added together. Shift-Ctrl-Clicking the arrow layer creates selections of both the heart and arrow shapes:
Creating selections in this way preserves transparency. In this example, I have a layer with a shape created with the airbrush tool, where the outer edges are transparent. I ctrl-click that layer to create a selection:
I create a new layer (and turn off the original layer for demo purposes) with the selection still available:
I select the paint bucket tool and a different color, and click in the selection. The transparency of the edges is preserved!