Use Resize to change a clip's resolution, frame depth, and aspect ratio.
To access the Resize menu, use:
Batch, then select a node from the Node bin.
Timeline, then use Batch FX (see Creating Batch FX).
Timeline, then add Timeline FX from the Effects ribbon (see Adding Timeline FX).
Tools, then select from the menu (See Accessing Tools).
The Modular Keyer, then select a node from the Node bin.
This node accepts a front clip, and outputs a result.
You can also use Resize to pan and scan the destination image relative to the source. You can then select and animate the portion of the source clip that appears as the destination clip, and process to create the result image.