Working with alpha masks
Unlike clipping paths, which produce a hard edge primarily used for separating a foreground image from a background image, alpha masks can include transparency information to subtly blend a foreground image into a new background. To work with alpha masks in QuarkXPress, you must first create an alpha mask in an image-editing application such as Adobe Photoshop. You can then use the alpha mask in QuarkXPress.
The alpha mask on the flames allows the text in the background to show through.
To work with alpha masks in QuarkXPress, you’ll need to save them with the picture in a format that supports alpha channels.
To apply an alpha mask to the selected picture, choose an alpha channel from the Measurements palette’s Mask drop-down menu.