astro_image can read one image from a file and display it
        in a TCanvas.


The program can read either a FITS file with a FITS image, a ROOT file 
with a TFBaseImage class or an ASRO file with a TFBaseImage class.


Program parameters:

   filename:   Is the input file with the image. The extension defines 
               the data type.
              
   extension:  Defines the extension in FITS files or the circle number in 
               ROOT and ASRO files. The primary array in a FITS file has 
               extension number 1 and the first extension is number 2. In 
               ROOT and in ASRO files each image name has its own cycle 
               counter. Therefore several images can have the same cycle 
               number in a ROOT or ASRO file if they have different names. 
               If it is set to 0 the first image in the file with the 
               defined image name is displayed.

   imagename:  Is the name of the image or the extension name in FITS 
               files. It can be an empty string for FITS files, but must 
               be defined for ROOT and ASRO files.


Error Messages:
  
  error during reading parameters (-3003)
        This  message  shows  that  the program cannot read its parameter file  
        astro_image.par.  Properly the environment variable PFILES is not set. 
        PFILES should define the path  where  this parameter file is stored. 
        During installation  of  the AstroROOT package this parameter file is 
        copied to ${ISDC_ENV}/pfiles.
        See also in the installation guide at point 3 for an example to set 
        this environment variable.