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ppmtoacad(1) AMIGA (10 October 1991) 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(Reg.)
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
Page 1 (printed 3/1/94)
ppmtoacad(1) AMIGA (10 October 1991) ppmtoacad(1)
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(5)
AUTHOR
John Walker
Autodesk SA
Page 2 (printed 3/1/94)
ppmtoacad(1) AMIGA (10 October 1991) ppmtoacad(1)
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.
Page 3 (printed 3/1/94)