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ppmtoacad(1) Unix Programmer's 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
-------
specified, 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 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.
-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 -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.
-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.
10 October 1991 1
ppmtoacad(1) Unix Programmer's Manual ppmtoacad(1)
-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,
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 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
----- ---- ------ ------ -------
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 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 2