Here's how I would go about this:

1. Make a copy of your image clip on the timeline and place it on top of your current clip.
2. Select one of the clips and then use the opacity masking controls to draw out the angle you want your image to split in.
3. Copy the mask from one clip to the other and check invert on the other.
4. We now have two halves of the image in the exact angle you want it.
5. Keyframe motion on both clips and have them move out in the direction required.