Adobe Illustrator CS

Once you’ve created the opacity mask, you can use the thumbnails in the Transparency palette to work with both the mask and the artwork beneath it. Instead of one thumbnail as you saw before, there are now two thumbnails: the one on the left is the artwork, the one on the right is the mask. To edit the artwork, click the left thumbnail. If you look at your Appearance palette, you’ll notice that the object you have selected is a normal path that has a solid fill attributed to it. The name of the path displays with a dashed underline in both the Appearance palette and the Layers palette, indicating that it has an opacity mask applied. At this point, the mask itself is not editable, nor can it even be selected.

Clicking the Invert Mask button reverses a mask and, rather than having the color black appear as transparent, the color black represents areas that are opaque. The Transparency palette menu also has an option to set all new masks to be created so that they are inverted.

Clicking the right thumbnail selects the mask, allowing you to edit its attributes. Take a look at the Layers palette; doing so reveals something very interesting. Instead of displaying all of the layers and objects in your file, when you click the mask thumbnail, the Layers palette switches to display just the opacity mask. The title bar of your document also indicates that you are editing the opacity mask and not the art. These visual indications help you easily identify when you are editing art and when you are editing an opacity mask. To return to artwork editing mode, simply click again on the left thumbnail icon.

When you are editing either the artwork or the opacity mask itself, using the selection tool to move items will result in both the artwork and the mask moving together. The reason for this is that by default, a mask and its artwork are linked with each other, indicated in the Transparency palette by a link icon that appears between the two thumbnail icons.

Clicking the link icon allows you to move the mask and artwork independently of each other, and clicking between the thumbnails toggles the link behavior.