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)
