.TH ppmtoacad 1 "10 October 1991"
.IX ppmtoacad
.IX AutoCAD
.SH NAME
ppmtoacad - convert portable pixmap to AutoCAD database or slide
.SH SYNOPSIS
.na
.B ppmtoacad
'in 15n
.RB [ -dxb ]
.RB [ -poly ]
.RB [ -background
.IR colour ]
.RB [ -white ]
.RB [ -aspect
.IR ratio ]
.RB [ -8 ]
.RI [ ppmfile ]
.in -15n
.ad
.SH DESCRIPTION
Reads a portable pixmap as input.  Produces an AutoCAD\*R slide file or
binary database import (.dxb) file as output.
If no
.I ppmfile
is specified, input is read from standard input.
.SH OPTIONS
.TP
.B -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.
.TP
.B -poly
If the
.B -dxb
option is not specified, the output of
.B ppmtoacad
is an AutoCAD slide file.  Normally each row of pixels is
represented by an AutoCAD line entity.  If
.B -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.
.TP
.BI -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
.B -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.
.TP
.B -white
Since many AutoCAD users choose a white screen background, this option
is provided as a short-cut.  Specifying
.B -white
is identical in effect to
.BR "-background 7" .
.TP
.BI -aspect " ratio"
If the source pixmap had non-square pixels, the ratio of the pixel
width to pixel height should be specified as
.IR 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
.BR "-aspect 0.8333" .
.TP
.B -8
Restricts the colours in the output file to the 8 RGB shades.
.PP
All flags can be abbreviated to their shortest unique prefix.
.SH 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.
.PP
.B 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.
.PP
When creating a .dxb file or a slide file with the
.B -poly
option,
.B 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.
.PP
Output files can be huge.
.SH "SEE ALSO"
AutoCAD Reference Manual:
.I Slide File Format
and
.IR "Binary Drawing Interchange (DXB) Files" ,
.BR ppm (5)
.SH AUTHOR
.RS 5
.nf
John Walker
Autodesk SA
Avenue des Champs-Montants 14b
CH-2074 MARIN
Suisse/Schweiz/Svizzera/Svizra/Switzerland
.PD 0
.TP 9
Usenet:
kelvin@Autodesk.com
.TP
Fax:
038/33 88 15
.TP
Voice:
038/33 76 33
.fi
.RE
.PD
.PP
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.
.PP
AutoCAD and Autodesk are registered trademarks of Autodesk, Inc.
