ppmtoacad



Ppmtoacad User Manual(0)                              Ppmtoacad User Manual(0)




NAME

       ppmtoacad - convert PPM to Autocad database or slide



SYNOPSIS

       ppmtoacad

       [-dxb]

       [-poly]

       [-background color]

       [-white]

       [-aspect ratio]

       [-8]

       [ppmfile]

       You may abbreviate any option to its shortest unique prefix.




DESCRIPTION

       This program is part of Netpbm(1).

       ppmtoacad  reads  a  PPM  image as input and produces an Autocad® slide
       file or binary database import (.dxb) file as  output.   If  you  don’t
       specify ppmfile, ppmtoacad takes the input from Standard Input.

       (Typographical  note: the name of Autocad is often rendered as AutoCAD.
       Netpbm documentation uses standard American typography, wherein that is
       not a valid form of capitalization).



OPTIONS

       -dxb   ppmtoacad  writes an Autocad binary database import (.dxb) file.
              You read this file with the DXBIN command and, once  loaded,  it
              becomes  part  of  the  Autocad geometrical database, so you can
              view and edit it like any other object.  Each sequence of  iden-
              tical 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 you don’t specify the -dxb  option,  ppmtoacad  generates  an
              Autocad  slide file.  Normally each row of pixels is represented
              by an Autocad line entity.  If you specify -poly, ppmtoacad ren-
              ders  the pixels as filled polygons.  If you view the slide on a
              display with higher resolution than the source image, this  will
              cause  the  pixels  to  expand  instead of appearing as discrete
              lines against the screen background  color.   Regrettably,  this
              representation  yields  slide  files  which  occupy more storage
              space and take longer to display.


       -background color
              Most Autocad display drivers can be configured to use any avail-
              able  color as the screen background.  Some users prefer a black
              screen background, others white, while splinter groups  advocate
              burnt  ocher,  tawny puce, and shocking gray.  Discarding pixels
              whose closest Autocad color representation is equal to the back-
              ground  color  can  substantially reduce the size of the Autocad
              database or slide file needed to represent  a  bitmap.   If  you
              don’t  specify  -background,  ppmtoacad assumes the screen back-
              ground color to be black.  You may  specify  any  Autocad  color
              number as the screen background; ppmtoacad assumes color numbers
              to specify the hues defined in the standard  Autocad  256  color
              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 image had non-square pixels (which means it is not
              standard PPM), specify the ratio of the  pixel  width  to  pixel
              height  as ratio.  ppmtoacad will correct the resulting slide or
              .dxb file 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 colors in the output file to the 8 RGB shades.




RESTRICTIONS

       Autocad has a fixed palette of 256 colors, distributed along  the  hue,
       lightness,  and  saturation axes.  So it may poorly render images which
       contain many nearly-identical colors, or colors  not  closely  approxi-
       mated by Autocad’s palette.

       ppmtoacad  works  best  if the system displaying its output can display
       the full 256 color Autocad palette.  Monochrome, 8 color, and 16  color
       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
       color  but it’s no substitute for true raster to vector conversion.  In
       particular, this process does not optimize thin diagonal lines at  all.

       Output files can be huge.



SEE ALSO

       Autocad  Reference  Manual: Slide File Format and Binary Drawing Inter-
       change (DXB) Files, ppm(1)



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.



netpbm documentation            10 October 1991       Ppmtoacad User Manual(0)

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