There are a bunch of tools for adding annotation to an image. You can fire up any number of image editors and then place text on top and add lines and such. I’ve found that this is typically too manually intensive for me. Normally, I just want to put a box around something and add a label. For that OmniGraffle is perfect.
Here’s a quick screencast showing how you might use OmniGraffle to annotate an image:
OmniGraffle is like Visio, but better. I’ve been able to export swimlane documents from OmniGraffle to Visio and have them work just fine. If you have multiple canvases in an OmniGraffle doc, they’ll be exported as a multi-page Visio doc.
OmniGraffle is a good program to have on hand for quick annotation or for creating documents with nodes and connections.
