ppmtoacad
convert portable pixmap to AutoCAD database or slide
Synopsis
ppmtoacad
[-dxb] [-poly] [-background
colour] [-white] [-aspect ratio]
[-8] [ppmfile]
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description
Reads a
portable pixmap as input. Produces an AutoCAD® 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.
-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
author
John Walker
Autodesk SA
Avenue des Champs-Montants 14b
CH-2074 MARIN
Suisse/Schweiz/Svizzera/Svizra/Switzerland
Usenet:
kelvin[:at:]Autodesk[:dot:]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.