Creating & Editing Layer Masks
You can obscure an entire layer or layer set, or just a selected part of it, using a layer mask. You can also edit a layer mask to add or subtract from the masked region. A layer mask is a grayscale image, so what you paint in black will be hidden, what you paint in white will show, and what you paint in gray shades will show in various levels of transparency.
To add a mask that shows or hides a selection:
1. In the Layers palette, select the layer or layer set to which to add a mask.
2. Select the area in the image, and do one of the following:
• Click the New Layer Mask button in the Layers palette to create a mask that reveals the selection.
• Choose Layer –> Add Layer Mask –> Reveal Selection or Hide Selection.
To edit a layer mask:
1. Click the layer mask thumbnail in the Layers palette to make it active.
2. Select any of the editing or painting tools.
Note: The foreground and background colors default to grayscale values when the mask is active.
3. Do one of the following:
• To subtract from the mask and reveal the layer, paint the mask with white.
• To make the layer partially visible, paint the mask with gray.
• To add to the mask and hide the layer or layer set, paint the mask with black.
To edit the layer instead of the layer mask, select it by clicking its thumbnail in the Layers palette. The paintbrush icon appears to the left of the thumbnail to indicate that you are editing the layer.
To paste a copied selection into a layer mask, Alt-click (Windows) or Option-click (Mac OS) the layer mask thumbnail in the Layers palette to select and display the mask channel. Choose Edit –> Paste, drag the selection in the image to produce the desired masking effect, and choose Select –> Deselect. Click the layer thumbnail in the Layers palette to deselect the mask channel.