AutoMask! Photoshop Plug-In

From HumanSoftware:

AutoMask! is a Masking Filter Plug-In for Photoshop (Elements), Corel PhotoPaint, Jasc PaintShopPro.

It features Global Density Masking:
The density masking action occurs all over the selected area. With the Global density, you can pick several colors, RGB or CMYK, and create a mask on these selected areas. This Global Density also lets users select any color that they want to protect from being covered a mask ( Protective density ).
The Global Density technique is especially useful when the subject is against a flat color background. In this case you have to select the color of the background and your mask is done! A special Virtual Masking Brush eliminates extra spots or unwanted mask created via the automatic density action. It is very common to have the same color inside your subject and outside, this is why the virtual masking/unmasking airbrush is useful! The brush is virtual because it works at the same speed whatever your picture size and may be used on very large images.

Local Brush Density Masking:
As you move along the edge of the subject, you can sample the image with the Density Brush Picker. The selected color is used to build a mask automatically along the edge.
An unlimited number of readings can be taken. Undo is possible. Users can go back and forth between any masking feature at any point. The local brush may be used in combination with the global density tool.
The main strength of the AutoMask density brush masking tool is the smoothness on the edge. AutoMask respects the natural antialiasing of the subject and the semi-transparency of the edges The mask created comes as an opacity layer or as a fourth or a fifth channel on a background image. AutoMask is the perfect tool for all the difficult silhouettes : trees, landscape, furs, animals...