A_LASER (Apple Laserwriter Program)

          Robert B. Goldstein
          Eye Research Institute of Retina Foundation
          20 Staniford St
          Boston, MA 02114
          (617) 742-3140


               A_LASER is a program that read a grey-scale image  into
          VAX memory and produces an ASCII output postscript file that
          can be directly copied to an Apple Laserwriter to print  the
          image.   The output file is always named a_laser.ps, however
          a command file is included that invokes a_laser, renames the
          output  file,  and queues the output file to a printer queue
          (PRLW.COM)

               Presently, the bulk of A_LASER is the code to read  the
          image  into  VAX memory in the first place.  This subroutine
          is imlod_2.  Since most sites will have their own format for
          images, the programmer should replace this code with his own
          routines.   For  our  site,  the  input  image   sizes   are
          restricted   to  128,  256,  or  512  square  images.   This
          restriction carries over to the  A_LASER  program,  but  can
          probably  be  easily  eliminated.   An  image  of  a GIRL is
          provided, and ALASER should correctly operate on this image.
          It  is  nessary  to define the symbol PIX:  to point the the
          current directory (ie - assign [] pix).

               A_LASER then converts the input  image  to  Postscript.
          The  program  uses  the  IMAGE  function  in  postscript  to
          accomplish this, and also sends  the  images  in  strips  to
          eliminate memory overflows within the laserwriter.

          ___________ __ ____
          Description of PRLW
               The command to use to print an image is
                $ prlw  imagename  size_in_inches  copies
               The size_in_inches and copies can be omitted.

               For example, to print 3 copies of GIRL, each 5 inches large,
               you issue
                prlw girl 5 3

               The command
                prlw clbcar
               will print one copy of the cblcar image, using its default size.


          Some technical details of what prlw does:
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                    prlw writes an auxiliary commmand file  that  runs
               the  a_laser  program.  A_laser produces a file, called
               a_laser.ps, which contains the postscript  commands  to
               convert the image to printable form.  prlw then renames
               alaser.ps to be imagename.ps, then sends  the  file  to
               the  new  queue  named  lw.   The  auxil  command  file
               prlw.com is automatically deleted.  The postscript file
               imagename.ps  is deleted upon sucessful printing by the
               queue manager.

                    A new device, called laserwriter  ,  was  defined,
               and  a  queue  started on it.  The name of the queue is
               lw.

                    To abort the printing of an image after it is sent
               to the lw queue, you issue
                stop/abort lw