Radiance ra_xyze program

RA_XYZE(1)                                                          RA_XYZE(1)

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  multi-
       plier  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  infor-
       mation  may  be  fully  recovered  later.  It is not necessary that the
       input file by 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 representa-
       tion 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 for-
       mat  except  for  conversion or display, in which case the correct pri-
       maries 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 for-
       mat:

         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), ra_rgbe(1), rpict(1)

RADIANCE                            5/30/96                         RA_XYZE(1)