Alpha Keys
Alpha-based keys use the clip’s alpha channel to define transparent areas of the image (Figure 13.38).
Figure 13.38. Alpha-based keys use the clip’s alpha channel to define transparent areas of the image.
As you may recall from Chapter 2, an alpha channel can be a straight alpha channel (like the one you can save as the fourth channel of a Photoshop image), or it can be premultiplied with color (such as the empty areas of Illustrator artwork). The kind of alpha channel the clip contains determines the type of key that you choose. For more about alpha channels, see Chapter 2.
When you add a title created in the Title Designer (see ...
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