Using Quick Mask mode, you can modify (or create) a selection using pixel-editing tools.
When entering this mode, your selection is temporarily presented as a pixel mask. Pixels can be added or erased using the standard Painting and Erase tools.
Painting in black will erase areas from the selection.
Painting in white will add areas to the selection.
Painting a grey will vary the opacity of the selection depending on the tone of grey used.
Erased areas are always removed from a selection.
By default, the Quick Mask is presented in the workspace as a translucent red overlay. The red areas are not included in the selection. This default view can be changed to show the masked area as black, white or transparent depending on your preferences.
To edit a selection using Quick Mask mode:
Do one of the following:
On the Toolbar, click Quick Mask.
From the Select menu, select Edit Selection As Layer.
Click or drag on the page using any pixel-editing tool.
Repeat step 1 to exit Quick Mask mode and display the selection as a marquee.
(Optional) To create a layer mask using the current selection, from the Layer menu, select New Mask Layer.
To change Quick Mask view:
On the Toolbar, click the arrow next to Quick Mask Enabled and then select a Show As option from the pop-up menu.