RA_TIFF(1)						      General Commands Manual							RA_TIFF(1)

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 deter-
       mined 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 stan-
       dard  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)

RADIANCE
							      8/29/97								RA_TIFF(1)