Looking for a bitmap editor that can do call-outs

Hi, all,

I recently test-drove Shutter and expect to be using it as my main screengrab program. But it seems to be missing some features that are important to me. I'm writing in hope of being told Shutter can do what I'm after or, failing that, hopefully a pointer to an app that I could use in conjunction with Shutter for the purpose.

I've been looking for quite a while for a bitmap editor capable of superimposing call-outs that include text on a bitmap image. I'm not really choosy when it comes to the design of the callouts, but I have a strong need to annotate screen grabs for purposes of writing software documentation. So for example, I'd like to have an ability to create several bordered boxes with text in them that each have a line running from it to a particular part of a dialog's screengrab. Or the callouts might be more like the balloon with a pointer used in comic strips for character's dialogs.

I can draw freehand to create such an effect, but I wind up with sloppy and wildly variable callouts, which tends to focus the eye on my poor artwork rather than the information in the call-out.

A very big plus would be text in call-outs that is accessible by those with visual deficits.

Can Shutter do this or do you have an app to suggest? Thanks in advance.