Ppmtoacad User Manual(0) Ppmtoacad User Manual(0)NAMEppmtoacad - convert PPM to Autocad database or slide
SYNOPSISppmtoacad
[-dxb]
[-poly]
[-background color]
[-white]
[-aspect ratio]
[-8]
[ppmfile]
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
You may abbreviate any option to its shortest unique prefix.
-dxbppmtoacad 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)
