Create a mask by painting

Choose Windows > Editors > Canvas Layer Editor and paint the regions of the mask layer you want to act as a mask.

You can create a mask by painting directly onto a mask layer. Areas of the layer that contain paint will masked, and areas of the layer that do not contain paint will be unmasked. Areas of the layer that contain partially transparent paint will be partially masked.

To create a mask by painting

Select the image layer you want to mask.
See Select an image layer.
In the Canvas Layer Editor choose Layer > New mask layer.
A new mask layer is created in the lower part of the editor, and automatically selected. The mask is also automatically associated to the image layer you selected in step 1.
Select a brush and paint the regions that you want to mask.
See Paint and erase.

Note
Any number of mask layers can be associated with an image layer. When you click on an image layer name, the associated mask layers are highlighted in lavender, and the small box icon to the right of their name displays a chain link icon .