ppmtoacad Man page

ppmtoacad General Commands Manual ppmtoacad

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® slide file or
binary database import (.dxb) file as output. If no ppmfile is speci‐
fied, 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 repre‐
sented 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 avail‐
able 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 Auto‐
CAD 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 identi‐
cal 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 320×200 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, ppm‐
toacad 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 Inter‐
change (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, with‐
out 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

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