What is a Mask?
A mask is a greyscale raster layer—transparent or opaque—that covers portions of underlying layers. Masks are generally used to hide details you don’t want visible in an image.
Mask layers affect all underlying layers. For this reason, a mask layer can never reside at the bottom of the stacking group.
Creating a Mask
You can create a mask in several ways, but the most common use images or selection areas to define the shape.
To create a mask from an image:
- Open the image you want to use for the mask.
Tip:
Paint Shop Pro includes some sample masks in the Masks folder.
- Open the image you want to mask—that is, the image file in which you want to use the mask.
- If your main image file contains more than one layer, select the layer you want to mask by clicking on it in the Layers palette.
- From the Layers menu, select New Mask Layer, and then From Image.
If you’re prompted to promote the target (background) layer to a full layer, click OK.
The Add Mask From Image dialog opens.
- From the Source window drop-down menu, select the mask image (the first image you opened).
- Under Create mask from, three mask options are available:
- With Source luminance, the mask is created based on the luminance of the pixels in the image, so lighter pixels produce less masking than darker pixels. This is a good option in most cases, and is used for the screenshots here.
- With Any non-zero value, any pixels in the mask image that aren’t transparent are used to produce the mask.
- With Source opacity, the mask is created based on the opacity of the mask image, so more transparent pixels produce more masking, and opaque pixels produce no masking.
Note:
Invert mask data reverses the transparency of the mask, turning black pixels white and white pixels black.
- Click OK.
The mask is applied to the image. Below, the mask is used to give the image a torn effect around the edges:
Notice that the mask layer and the image layer are now grouped in the Layers palette:
This means that the mask layer affects only the layer you initially selected. If you have additional layers in the image, and you want the mask to be applied to all of them, you can drag the mask layer from its current group up to the main level, above the other layers.
You can also create a mask from a selection using the Selection 
tool, the Freehand Selection 
tool, or the Magic Wand 
tool:
- Open the image you want to apply the mask to.
- Use one of the selection tools to create a selection of any shape. You’ll be able to mask either the contents of the selection or everything but the contents of the selection.
- From the Layers menu, select New Mask Layer, and then either Show Selection or Hide Selection.
The following was accomplished by choosing Show Selection:
With a little creativity, there’s no end to the effects you can create with masks. For instance, by using the Flood Fill 
tool to fill a mask created from a selection with a gradient, and then reducing the opacity of the mask layer, you can apply a semi-transparent gradient to an object without altering the object itself:
Paint Shop Pro Training Course Part 3: Section 1 Review
In this section, you learned about:
- Using layers
- Selecting layers
- Adding and deleting layers
- Changing layer order
- Viewing and hiding layers
- Adjusting the opacity of layers
- Masking
- Creating a mask
