The `image' command

Suppose you have a data file `a_file.sdf' with an image, i.e. a two-dimensional data set and want to plot is on an X display. This is one of the most common actions in Figaro. Most users will use the `image' command for this purpose. In general it uses a different display window than where most other plots go. The idea is that most plots are line plots and their device is selected with the command `soft'. But `image' should display at least in grey, if not in false colours. So you have to specify the imaging device separately, although it can be the same actual device as the `soft' device.

Consider the following sequence of commands:

   % xdisplay
   ICL> idev xw
   ICL> colour grey
   ICL> image a_file accept

If you are not familiar with the necessities of using X windows over the computer network, see the section on plotting a spectrum.

The second command tells Figaro which graphics device you want to use. `xw' is an abbreviation for `xwindows'. Together with the information from `xdisplay' this is sufficient to open the window. You should now get a display window on your screen, and a box with the words `PGPLOT imaging' in the centre is drawn into the window. You need to give the `idev' command only once. Figaro will always remember that you want to use the device `xw'.

The third command changes the display window to show various levels of grey as representation of the image data values. A new display window may have an undefined `colour lookup table', or a different plot command may have changed the lookup table. The `colour' command with parameter `grey' always brings it back to normal.

The fourth command finally displays the image contained in the file `a_file.sdf'. Data files can have names ending with `.sdf' or `.dst'. They must not contain any additional periods. The Figaro commands know about this, and must not be given this file name extension.

The keyword `accept' prevents the command from prompting you for information that it can guess itself. Unfortunately, you don't know what it did guess, and you might never learn how you can exert more control over the display.