The GRAPHIC Program

GRAPHIC is essentially VECTOR and GreGcombined in a single program. In addition, it includes access to a ``current image'' and the following commands to handle this image and catalogs:

 ASTROMETRIC     : Plots astrometric star positions (for finding charts)
 HEADER          : Give the Header of the current Image.
 IMAGE [Filename]: Read the gildas image Filename. 
 IRAS Band       : Select and plot IRAS sources of a given band
 KILL            : Kills pixels in the current image
 PSC_IRAS        : Get characteristics of IRAS point source
 REGRESSION [Val]: Computes regression lines
 SPECTRUM        : Extract a spectrum from the current image.

The GRAPHIC program uses GreG to display images, either in bitmaps or contour levels, with full user control over the image boundaries, user coordinate limits, etc...

Three specific commands deal with GILDAS images:

• IMAGE 
  Read an image or a subset of an image in the "Regular Grid" area of GreGThis command allows to have access to individual planes of a 3-D or 4-D data cubes for contouring, perspective plotting, pixel value interrogation by using the GreG GREG2 $\backslash$ language. All relevant information is transmitted to GreG: user coordinate values, coordinate system, projection used if any, blanking values.
• HEADER 
  Displays the header of the currently mapped image, or a specified image.
• SPECTRUM 
  Extracts a spectrum from the currently mapped image by putting the values of the specified column in GreG buffer Y and the corresponding coordinates, computed from the header information, in GreG buffer X.
  (i.e. X(i) = (i-Xref)*Xinc + Xval for i=1 to NX)
• KILL  delete bad pixels, provided the image has been opened with Read-Write access.

By default, GRAPHIC opens the input image in ReadOnly, so that it will never alter them unless specifically requested. To do so image should be accessed with   ReadWrite access (option /WRITE of command IMAGE). Even in this case, commands in the GREG2 $\backslash$ language never modify the image mapped by GRAPHIC; only commands from the language GRAPHIC $\backslash$ can do so.