xenial (1) ra_xyze.1.gz

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)