Layer masking

Masking originated as a technique for creating color separations, where sheets of masking material were hand-cut to define the color regions in an image. In the Corel Painter digital workspace, the layer mask is a powerful tool for controlling image composition and effects. Unlike permanently erasing and deleting content from a layer, layer masking is a non-destructive way to conceal areas of a layer.

Layer masks vs. channels

A layer mask is similar to an alpha channel. Both are grayscale images that you can create and edit; however, their characteristics and functions are different:

A layer mask is attached to a layer, but an alpha channel is independent.
The canvas can have up to 32 alpha channels; each layer can have only one layer mask.
Channels don’t influence the visibility of the canvas image; a layer mask defines what areas of a layer’s image are visible.
An alpha channel, when loaded, protects designated areas of an image; a layer mask does not provide protection.
A channel is enabled by loading it to a selection. A layer mask can be enabled and disabled at any time, and it can also be loaded to a selection.

The Channels panel provides access to both channels and layer masks. For more information about channels, see Creating and copying channels.

Layer masking workflow

First, select a layer and create a layer mask. If you want to define the visible and concealed areas by painting, create a blank layer mask. You can also create a mask based either on a selection or the transparency of the selected layer. Where the mask is white, the layer content is fully visible; where the mask is black, the layer content is hidden. Shades of gray in the mask represent varying degrees of transparency in the layer; areas filled with darker shades of gray appear more transparent than areas filled with lighter shades.

Next, select the layer mask in the Layers panel, and choose a compatible brush. Some variants, such as brushes from the Thick Paint, Liquid Ink, Watercolor, Real Watercolor, Selection, Erasers, and Impasto categories, cannot be used on layer masks. You can set brush attributes such as size, opacity, dab profile, hardness, and expression now, or you can adjust them later as you paint. You can also use the Paint Bucket and Interactive Gradient tools to quickly fill an area or create a soft and gradual transition between pure black and pure white, respectively.

Finally, start painting in the document window. To conceal areas of the layer, paint with pure black at full opacity; to reveal areas of the layer and bring back details, paint with pure white. Painting with gray will result in partial transparency. The lighter the shade of gray you use, the less transparent the area of the layer will be; the darker the shade of gray, the more transparent the area will be. To control the shades of gray, adjust brush opacity. Since the brush is loaded with pure black, changing the brush opacity will result in varying shades of gray. Switch back and forth between painting with black, white, and gray to fine-tune the layer mask and find the right balance.

The following table provides links to the help topics that contain detailed information about the main steps for creating a layer mask.


Workflow step
Help topic
1 Create a layer mask
2 Select a layer mask
3 Paint on a layer mask

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