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NAME

       ppmtoacad - convert portable pixmap to AutoCAD database or slide

SYNOPSIS

       ppmtoacad [-dxb] [-poly] [-background colour] [-white] [-aspect ratio]
               [-8] [ppmfile]

DESCRIPTION

       Reads a portable pixmap as input.  Produces an AutoCAD® slide  file  or
       binary  database  import  (.dxb)  file  as  output.   If  no ppmfile is
       specified, input is read from standard input.

OPTIONS

       -dxb   An AutoCAD binary database import (.dxb) file is written.   This
              file  is  read  with the DXBIN command and, once loaded, becomes
              part of the AutoCAD geometrical database and can be  viewed  and
              edited like any other object.  Each sequence of identical pixels
              becomes a separate object in the database; this  can  result  in
              very large AutoCAD drawing files.  However, if you want to trace
              over a bitmap, it lets you zoom and pan around the bitmap as you
              wish.

       -poly  If  the -dxb option is not specified, the output of ppmtoacad is
              an  AutoCAD  slide  file.   Normally  each  row  of  pixels   is
              represented  by  an  AutoCAD line entity.  If -poly is selected,
              the pixels are rendered as filled polygons.   If  the  slide  is
              viewed  on  a  display  with  higher  resolution than the source
              pixmap,  this  will  cause  the  pixels  to  expand  instead  of
              appearing  as  discrete  lines  against  the  screen  background
              colour.  Regrettably, this  representation  yields  slide  files
              which occupy more disc space and take longer to display.

       -background colour
              Most  AutoCAD  display  drivers  can  be  configured  to use any
              available colour as the screen background.  Some users perfer  a
              black  screen  background,  others  white, while splinter groups
              advocate burnt ocher, tawny puce, and shocking grey.  Discarding
              pixels  whose  closest AutoCAD colour representation is equal to
              the background colour can substantially reduce the size  of  the
              AutoCAD database or slide file needed to represent a bitmap.  If
              no -background colour is specified, the screen background colour
              is  assumed  to  be  black.   Any  AutoCAD  colour number may be
              specified as the screen background; colour numbers  are  assumed
              to  specify  the hues defined in the standard AutoCAD 256 colour
              palette.

       -white Since many AutoCAD users choose a white screen background,  this
              option  is  provided  as  a  short-cut.   Specifying  -white  is
              identical in effect to -background 7.

       -aspect ratio
              If the source pixmap had non-square pixels,  the  ratio  of  the
              pixel  width  to pixel height should be specified as ratio.  The
              resulting slide or .dxb file will be corrected so that pixels on
              the  AutoCAD  screen will be square.  For example, to correct an
              image made  for  a  320x200  VGA/MCGA  screen,  specify  -aspect
              0.8333.

       -8     Restricts the colours in the output file to the 8 RGB shades.

       All flags can be abbreviated to their shortest unique prefix.

BUGS

       AutoCAD  has a fixed palette of 256 colours, distributed along the hue,
       lightness, and saturation axes.  Pixmaps  which  contain  many  nearly-
       identical  colours,  or  colours  not closely approximated by AutoCAD’s
       palette, may be poorly rendered.

       ppmtoacad works best if the system displaying its output  supports  the
       full  256  colour AutoCAD palette.  Monochrome, 8 colour, and 16 colour
       configurations will produce less than optimal results.

       When creating a .dxb file or  a  slide  file  with  the  -poly  option,
       ppmtoacad  finds  both vertical and horizontal runs of identical pixels
       and consolidates them into rectangular regions to reduce  the  size  of
       the  output  file.   This  is  effective for images with large areas of
       constant colour but it’s  no  substitute  for  true  raster  to  vector
       conversion.   In  particular,  thin diagonal lines are not optimised at
       all by this process.

       Output files can be huge.

SEE ALSO

       AutoCAD  Reference  Manual:  Slide  File  Format  and  Binary   Drawing
       Interchange (DXB) Files, ppm(5)

AUTHOR

            John Walker
            Autodesk SA
            Avenue des Champs-Montants 14b
            CH-2074 MARIN
            Suisse/Schweiz/Svizzera/Svizra/Switzerland
            Usenet:  kelvin@Autodesk.com
            Fax:     038/33 88 15
            Voice:   038/33 76 33

       Permission  to  use, copy, modify, and distribute this software and its
       documentation for any  purpose  and  without  fee  is  hereby  granted,
       without any conditions or restrictions.  This software is provided ‘‘as
       is’’ without express or implied warranty.

       AutoCAD and Autodesk are registered trademarks of Autodesk, Inc.

                                10 October 1991                   ppmtoacad(1)