Printing your graph.

IDL treats the screen as one device and a postscript file as another.

Switch devices with the set_plot command:

IDL> set_plot,'ps'

will switch to postscript output and

IDL> set_plot,'x'

will switch back to the screen.

The device command allows you control which postscript file your output goes to, how big your plot will appear etc.

If you want a .png, .jpeg etc file plot it in a graphics window, using

IDL> set_plot,'x'

then read it to file using

IDL> filename='~username/blah.png'
IDL> write_png,filename,tvrd()

Alternatively, use

IDL> set_plot, 'z'
IDL> device, set_resolution=[640,680]
IDL> plot, x, y etc...
IDL> write_png, 'filename.png',tvrd()