ppmtoacad(1)ppmtoacad(1)NAMEppmtoacad - convert portable pixmap to AutoCAD database or
slide
SYNOPSISppmtoacad [-dxb] [-poly] [-background colour] [-white]
[-aspect ratio] [-8] [ppmfile]
DESCRIPTION
Reads a portable pixmap as input. Produces an AutoCAD
slide file or binary database import (.dxb) file as out
put. If no ppmfile is specified, input is read from stan
dard 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 geo
metrical database and can be viewed and edited like
any other object. Each sequence of identical pix
els 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 ren
dered 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 repre
sentation 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 -back
ground 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 -back
ground 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 Auto
CAD screen will be square. For example, to correct
an image made for a 320x200 VGA/MCGA screen, spec
ify -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 pre
fix.
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 conver
sion. In particular, thin diagonal lines are not opti
mised 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 soft
ware 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)
