png editing suggestion

[Jack]

Can someone recommend a relatively simple application for minor editing  
of png files for a docbook manual?  At minimum, I need to crop some  
images.  Being able to overlay small amounts of text is also useful.  I  
know I can use GIMP for this, but it seems to take me lots of time to  
relearn it every time I need to do something simple.

The cause here is that Spectacle has captured a number of screenshots  
(active window) with some type of border around the windows, which I  
think should be removed before using.  (This is something outside the  
regular  window border.)  Any hints on why spectacle might be acting up  
would also be welcome, but  I'll raise that as a separate issue at a  
later time.

Thanks for any suggestions.

Jack