This commands adds to the existing selection the pixels of the active layer corresponding to pixels with more than 0% opacity in the layer mask. White pixels (100% opaques) in layer mask will give pixels fully selected in the image. Grayscaled pixels (1%-99% opaques) will give a feathered selection. Black pixels (0% opaques) will not be selected. Pixels are not actually added: they are included in the selection. The layer mask is not modified by this command.
Figure 10.75. Illustration of Add layer mask to Selection
From left to right: original image with a selection, layer dialog with a layer mask created with the “Layer's alpha channel” option, after adding layer mask to selection.