NAME

       ra_xyze - convert between RADIANCE RGBE and XYZE formats

SYNOPSIS

       ra_xyze  [  -r  ][  -e exposure ][ -o ][ -c | -u ][ -p xr yr xg yg xb yb xw yw ] [ input [
       output ] ]

DESCRIPTION

       Ra_xyze  converts  between  RADIANCE  RGBE   (red,green,blue,exponent)   and   XYZE   (CIE
       X,Y,Z,exponent)  formats.   The -e option specifies an exposure compensation, which may be
       given as a decimal multiplier or in f-stops (powers of two).  The -o option may be used to
       specify  original  units,  to  which the exposure compensation is applied.  Otherwise, the
       multiplier is in addition to  any  previous  exposure  adjustment.   By  default,  ra_xyze
       produces  a  flat  XYZE RADIANCE picture file from any type of RADIANCE input picture.  To
       override these defaults, the -c option may be used to specify run-length  encoded  output,
       or the -u option may be used to specify a flat output.

       The  -r option causes ra_xyze to produce a run-length encoded RGBE file instead, unless -u
       is given, also, when it will produce a flat RGBE file.  The  -p  option  may  be  used  to
       override  the  standard  RADIANCE  RGB primary colors to tailor the image for a particular
       output device or representation.  The eight floating-point arguments to  this  option  are
       the  1931  CIE  (x,y)  chromaticity  coordinates of the three RGB primaries plus the white
       point, in that order.  The new primaries will be recorded in  the  header  of  the  output
       file,  so that the original information may be fully recovered later.  It is not necessary
       that the input file be in XYZE format.  Th -r option may therefore be used to convert from
       one RGB primary representation to another using the -p option.

       If  the output file is missing, the standard output is used.  If the input file is missing
       as well, the standard input is used.

NOTES

       The CIE standard used is the 1931 2-degree observer, and the correct output representation
       relies  on  the original RADIANCE input description being defined properly in terms of the
       standard RADIANCE RGB primaries, whose CIE (x,y) chromaticity values are  defined  in  the
       header  file  in  src/common/color.h.   In  this  same file is a standard for the luminous
       efficacy of white light (WHTEFFICACY), which is used as a conversion  between  lumens  and
       watts throughout RADIANCE.  This same factor is applied by ra_xyze when converting between
       the radiometric units of the RGBE format and the photometric units  of  the  XYZE  format.
       The  purpose of this factor is to ensure that the Y component of the CIE representation is
       luminance in units of candelas/meter^2.

       Most of the RADIANCE picture filters should work uniformly on either RGBE or  XYZE  files,
       so it is not necessary to convert back to RGBE format except for conversion or display, in
       which case the correct primaries for the chosen output device should be specified with the
       -p option if they are known.

EXAMPLES

       To convert RGBE output from rpict(1) into run-length encoded XYZE format:

         rpict [options] scene.oct | ra_xyze -c > scene_xyz.hdr

       To prepare a RADIANCE picture for display on a calibrated NTSC monitor:

         ra_xyze -r -p .670 .330 .210 .710 .140 .080 .333 .333 stand.hdr ntsc.hdr

AUTHOR

       Greg Ward

BUGS

       Any  color  correction  applied  to  the  original  image  is not removed or translated by
       ra_xyze, and it may result in color shifts  in  the  output.   If  color  preservation  is
       important  and the correction is unwanted, it is best to remove it with pfilt(1) using the
       -er, -eg and -eb options first.  (Simply look at  the  header  and  apply  the  reciprocal
       primaries  of  all  COLORCORR=  lines multiplied together.)  Better still, get the picture
       before color correction is applied.

SEE ALSO

       pfilt(1), pvalue(1), ra_rgbe(1), rpict(1)