ppmtoacad

ppmtoacad(1)                General Commands Manual               ppmtoacad(1)

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(R) slide file or
       binary  database import (.dxb) file as output.  If no ppmfile is speci-
       fied, 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  repre-
              sented  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 avail-
              able 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 Auto-
              CAD  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 identi-
              cal 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, ppm-
       toacad 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 Inter-
       change (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, with-
       out 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)