The Subtract Alpha from Selection command
creates a selection in the current layer from the Alpha Channel. Opaque
pixels are fully selected, transparent pixels are unselected, and
translucent pixels are partially selected. This selection is
subtracted from the existing selection. The Alpha
channel itself is not changed.
7.41.1. コマンドの呼び出し方
You can access this command from the main menu through
Layer → Transparency → Subtract Alpha from Selection.
