Isolate Black / White

Developed for Paint.net users, Isolate Black / White is a plugin made to create a black and white copy of the current layer to apply it as the alpha mask. It features several advanced customization options for experienced users.

Easy integration with Paint.net

Installing it is a simple task because there is no actual setup pack involved, unlike regular software products. Instead, you can drop the downloaded DLL file in the "Effects" folder of Paint.net, start the utility, and access it from the "Color" submenu of the "Effects" menu.
This can be done even if you have a portable version of Paint.net, for example if it's stored on a removable storage device. If the image editor was already launched beforehand, you have to restart it.

Render an alpha mask and configure settings

The configuration panel of Isolate Black / White is small and contains a color wheel that enables you to pick the preferred color of the silhouette in your photograph. Alternatively, you can enter the numerical values of the red, green and blue channels.
By default, the new alpha channel is automatically blended with the picture. Apart from the fact that you can disable this, it's possible to invert the mask as well as to adjust the alpha transparency level by moving a slider. It can be reset to default.
Since the image effects can be previewed while tinkering with settings, you don't have to go through with them just to be able to verify results and remove the second layer or undo the action if you're not pleased with the outcome.

Evaluation and conclusion

The project hasn't been updated for a long time and doesn't seem to be in development anymore. However, no compatibility issues occurred in our tests when running Isolate Black / White from the most recent release of Paint.net.