NAME

       ra_ppm - convert RADIANCE picture to/from a Poskanzer Portable Pixmap

SYNOPSIS

       ra_ppm [ -r ][ -a ][ -b ][ -s maxv ][ -g gamma ][ -e +/-stops ] [ input [ output ] ]

DESCRIPTION

       Ra_ppm  converts  between  RADIANCE  and  Poskanzer Portable Pixmap formats.  The -g option specifies the
       exponent used in gamma correction; the default value is 2.2.  An exponent of  1  turns  gamma  correction
       off.   The  -e  option specifies an exposure compensation in f-stops (powers of two).  Only integer stops
       are allowed, for efficiency.  The -r option invokes a reverse conversion, from a  Pixmap  to  a  RADIANCE
       picture.   If  the  output file is missing, the standard output is used.  If the input file is missing as
       well, the standard input is used.

       The -a option produces a standard ASCII Pixmap representation instead of the default  binary  file.   The
       file  is  much  larger  and the conversion is much slower, which is why this format is not normally used.
       The -b option forces greyscale output.  The -s option controls the output scale, which is 255 by default.
       If this value is set above 255, then two bytes will be output for each component in  binary  mode.   This
       may not be understood by some PPM readers, which do not understand files with maximum values greater than
       255.  The maximum allowed setting for this parameter is 65535.

       With  the  -r  option,  the  type of the Pixmap input file is determined automatically.  Ra_ppm will read
       either greyscale or color Pixmaps, with any precision up to a maximum scale of 65535.

NOTES

       The Poskanzer Portable Bitmap Plus package contains translators between the Pixmap format and many of the
       dozen or so image file "standards" that exist.  At the time of this writing, the  software  is  free  and
       available by anonymous ftp from export.lcs.mit.edu (18.30.0.238) in the file "contrib/pbmplus.tar.Z".

AUTHOR

       Greg Ward

ACKNOWLEDGEMENT

       Work  on  this  program  was initiated and sponsored by the LESO group at EPFL in Switzerland and Silicon
       Graphics, Inc.

SEE ALSO

       pfilt(1), ra_bmp(1), ra_bn(1), ra_pr(1), ra_pr24(1), ra_t8(1), ra_t16(1), ra_tiff(1), ximage(1)

RADIANCE                                             2/10/99                                           RA_PPM(1)