How to save an IDL plot as a jpeg file:
                                                                      
If you want to save a plot from IDL as a JPEG, after you made your
plot in IDL you can type the following:

IDL> im=tvrd()   ;im is an array
IDL> write_jpeg,'filename.jpeg',im

You can then exit IDL, and in the directory you want to save the file,
type:

 xv filename.jpeg

Now your plot is saved as a JPEG file.