Tooling Special Effects
Photodesk has a reasonable selection of Special Effects available, but many of them operate only on whole images. You can't selectively apply them with the airbrush, for instance. True, you can mask off the parts of the image you don't want to affect, but this is slow, isn't interactive and feels rather clumsy compared to applying other effects.
Here's how you can locally apply a global Special Effect with any tool you like. Or at least, a very convincing facsimile thereof.
The basic idea is to copy the image on to a separate layer, apply the effect to the bottom layer, then paint transparent pixels on the topmost layer.
- Open the Layers window (Channels:Layers...).
- Drag and drop the name of the image to the New layer icon, as shown. This creates a copy of the image in a separate layer.
- Click on the bottom image's number (layer 0) to select this as the layer to work on.
- Apply your special effect to this layer and fix.
- Now click on the upper layer's number, and the Eye icon of the lower layer. The lower layer (with the applied special effect) isn't visible at present, because the upper layer is opaque.
- Open the Palette window, and select Transparency from the pull-down menu.
- Select a tool - the airbrush, for instance - and a brush size.
- Now start painting. As you paint, you'll see the effect used on the lower layer start to show through.
- All the standard facilities are available: local undo with Adjust, vary the tool's opacity, apply texture and gradient. It's nearly indistinguishable from applying the effect with a tool.
- When you're happy, select Layers>Merge visible layers and fix.