Creating Alpha Channels with Paint

Use Paint to draw directly on a layer's alpha channel. This is useful for retouching mattes or isolating a part of a clip.

To draw on a layer's alpha channel:

1. In an empty Composite operator, import a front layer and a back layer. In this example, the following layers are used.



2. In the Workspace panel, select the front layer.
3. Choose Operators | Paint.

The selected layer appears in Paint.

4. Choose Window | View Mode | Alpha Overlay.

The image does not change immediately, but when you draw on the alpha channel, semi-transparent red appears indicating areas of transparency.

Note: You do not see the composite in this view mode. However, you can set another viewport to show the result of the matte in context of the composite.

5. Click the Toolbar tab, then click the Filled Ellipse tool .
6. Click the color box to pick a paint color:
• Select black to remove areas from the front layer.
• Select varying shades of gray to create areas of partial transparency.
• Select white to add areas to the front layer.



Note: When you are working on the alpha channel, only grayscale colors ranging from white to black are available.

7. Draw a series of circles in the shape of "thinking bubbles."



8. When you have completed drawing on the alpha channel, choose Window | View Mode | Alpha to see what the alpha channel looks like.



9. Choose Window | View Mode | Normal.

You return to the normal view mode.

10. Click the Back button to return to the previous view or, in the Workspace panel, double-click the Composite operator.

You return to the composite (and can see what our subject is thinking about).