114 VIDEO EDITORWorking with mattesAnother feature of the Overlay Options dialog box is that it allows you to makeuse of mattes (or masks). In the film world, mattes work like color keying in thatthey show and hide various areas of the overlay clip. You can make any image orvideo file into a matte or you can create these yourself in a paint program such asVideo Paint or in CG Infinity.Creating image and video mattesImage mattes are great when you want to specify a particular area in the frame fora video to appear and need to get the cleanest possible blend when overlaying.To create an image matte:1. Run your favorite image editing software,such as Ulead PhotoImpact (Ulead VideoPaint or CG Infinity can also be used), andcreate a rectangle the same size as theframes in your video project.2. Draw an area where you want the video toappear, such as a circle or a square.3. Fill this area with a solid color (like blue) and then fill the background with acontrasting color (like green).4. Load this image into a video track (Video1).5. Right-click on the image and select Overlay Options.6. Select the Color Key from the Type list and click in the blue area. The bluearea is then keyed out to reveal the underlying clip.Video mattes are simply multiple image mattes spread out over multiple frames.These can be commonly created in many animation programs.To create a video matte:1. Create a sequence of images, such as a Targa animation (TGA).2. Insert them into Video Editor as a Ulead Image Sequence. (If you have UleadVideo Paint, you can also insert a Video Paint project file).When preparing an image or video for color keying, use a solid color as thebackground, such as blue. Do not use black or white as these colors tend to"bleed" into the overlay clip.
