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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 AutoCADĀ® 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)