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)