The Subtract from Selection command creates a selection in the image from the pixels of the active layer according to their transparency. Opaque areas are fully selected, transparent areas are unselected, and translucent areas are partially selected. This selection is subtracted from an existing selection. The alpha channel itself is not changed.

10.46.2.  Example

Figure 10.114.  Applying “Subtract from Selection”

Non-transparent pixels of the active layer have been subtracted from the existing rectangular selection.