At some point during your work on a storyboard image, you may find that you want to do something that would be easy in your favorite dedicated bitmap graphics editor (like Photoshop, Corel Draw, Paint Shop Pro, The GIMP, etc.) but difficult in Springboard. Just for these situations, Springboard supports editing a bitmap layer in an external program. You can use the features you're used to in your graphics editor while still benefiting from Springboard's storyboard structure.
The steps in the process are:
Troubleshooting External Editing