NAME

       ra_tiff - convert RADIANCE picture to/from a TIFF color or greyscale image

SYNOPSIS

       ra_tiff [ -z|-L|-l|-f|-w ][ -b ][ -e +/-stops ][ -g gamma ] { in.hdr|- } out.tif
       ra_tiff -r [ -x ][ -g gamma ][ -e +/-stops ] in.tif [ out.hdr|- ]

DESCRIPTION

       Ra_tiff  converts  between  RADIANCE  and TIFF image formats.  The -g option specifies the
       exponent used in gamma correction; the default value is  2.2,  which  is  the  recommended
       value for TIFF images.

       The  -b  option  can  be used to specify an 8-bit greyscale TIFF output file.  The type of
       input file is determined automatically.

       The -z option will result in LZW compression of the  TIFF  output  file.   The  -L  option
       specifies  SGILOG  compression,  which is recommended to capture the full dynamic range of
       the Radiance picture.  However, since many TIFF readers do not yet  support  this  format,
       use  this  option  under  advisement.  The -l option specifies SGILOG24 compressed output,
       which has less dynamic range than SGILOG, but may  be  smaller  in  some  cases.   (It  is
       usually larger.)  The -f option specifies 32-bit IEEE floating-point/primary output, which
       is the highest resolution format but results in very large files,  since  each  RGB  pixel
       takes  96  bits  (12  bytes)  and  does  not  compress  well.   The  -w  option  specifies
       16-bit/primary output, which is understood by some photo editing software, such  as  Adobe
       Photoshop.  Decompression is automatically determined for TIFF input.

       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 TIFF image to a RADIANCE picture.   The
       RADIANCE  picture file can be taken from the standard input or sent to the standard output
       by using a hyphen ('-') in place of the file name, but the TIFF image must be to or from a
       file.   The -x option can be used to specify an XYZE Radiance output file, rather than the
       default RGBE.

EXAMPLES

       To convert a Radiance picture to SGILOG-compressed TIFF format:

         ra_tiff -L scene1.hdr scene1.tif

       To later convert this image back into Radiance and display using  human  visibility  tone-
       mapping:

         ra_tiff -r scene1.tif scene1.hdr
         ximage -e human scene1.hdr

AUTHOR

       Greg Ward Larson
       Sam Leffler

ACKNOWLEDGEMENT

       Work on this program was initiated and sponsored by the LESO group at EPFL in Switzerland.
       Additions for the SGILOG data encoding were sponsored by Silicon Graphics, Inc.

BUGS

       Many TIFF file subtypes are not supported.
       A gamma value other than 2.2 is not properly recorded or understood  if  recorded  in  the
       TIFF file.

SEE ALSO

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