ppmtoacad - convert portable pixmap to AutoCAD database or slide
ppmtoacad [-dxb] [-poly] [-background colour] [-white] [-aspect ratio] [-8] [ppmfile]
Reads a portable pixmap as input. Produces an AutoCAD(R) slide file or binary database
import (.dxb) file as output. If no ppmfile is specified, input is read from standard
-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 data-
base and can be viewed and edited like any other object. Each sequence of identi-
cal 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.
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. Dis-
carding pixels whose closest AutoCAD colour representation is equal to the back-
ground 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.
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 cor-
rected so that pixels on the AutoCAD screen will be square. For example, to cor-
rect 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.
AutoCAD has a fixed palette of 256 colours, distributed along the hue, lightness, and sat-
uration 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 ver-
tical 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.
AutoCAD Reference Manual: Slide File Format and Binary Drawing Interchange (DXB) Files,
Avenue des Champs-Montants 14b
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)