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 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(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.