Ubuntu Manpage: ppmtoacad - convert portable pixmap to AutoCAD database or slide

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.

AUTHOR