I need an image viewer to help me see the XY coordinates inside an image (mouse cursor position relative to top left corner of the image). Could somebody please recommend one?
GIMP will do this.
sudo apt-get install gimp
I just discovered that Geeqie will do this as well (and it loads much faster than GIMP):
sudo apt-get install geeqie
Then in the menus click View >> Pixel Info and it'll show the pixel info (position and RGB !) in the status bar.
I use geeqie as my image viewer, and it has the ability to display all EXIF tags, as well as a histogram and other information in a sidebar by going to View --> Info Sidebar or View --> Exif Window...
It can be installed from the usual sources on Linux (aptitude, synaptic, etc.) with more info at http://www.geeqie.org/