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.\" SCCSid "@(#)ra_tiff.1 2.3 8/29/97 LBL"
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.TH RA_TIFF 1 8/29/97 RADIANCE
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.SH NAME
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ra_tiff - convert RADIANCE picture to/from a TIFF color or greyscale image
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.SH SYNOPSIS
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.B ra_tiff
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[
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.B "-z|-L|-l|-f|-w"
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][
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.B -b
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][
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.B "-e +/-stops"
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][
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.B "-g gamma"
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]
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{
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.B "in.hdr|-"
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}
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.B out.tif
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.br
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.B "ra_tiff -r"
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[
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.B \-x
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][
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.B "\-g gamma"
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][
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.B "\-e +/-stops"
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]
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.B in.tif
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[
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.B "out.hdr|-"
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]
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.SH DESCRIPTION
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.I Ra_tiff
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converts between RADIANCE and TIFF image formats.
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The
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.I \-g
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option specifies the exponent used in gamma correction;
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the default value is 2.2, which is the recommended value
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for TIFF images.
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.PP
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The
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.I \-b
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option can be used to specify an 8-bit greyscale TIFF output file.
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The type of input file is determined automatically.
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.PP
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The
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.I \-z
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option will result in LZW compression of the TIFF output file.
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The
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.I \-L
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option specifies SGILOG compression, which is recommended
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to capture the full dynamic range of the Radiance picture.
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However, since many TIFF readers do not yet support this format,
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use this option under advisement.
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The
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.I \-l
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option specifies SGILOG24 compressed output, which has
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less dynamic range than SGILOG, but may be smaller in some cases.
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(It is usually larger.)\0
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The
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.I \-f
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option specifies 32-bit IEEE floating-point/primary output, which
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is the highest resolution format but results in very large files, since
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each RGB pixel takes 96 bits (12 bytes) and does not compress well.
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The
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.I \-w
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option specifies 16-bit/primary output, which is understood by
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some photo editing software, such as Adobe Photoshop.
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Decompression is automatically determined for TIFF input.
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.PP
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The
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.I \-e
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option specifies an exposure compensation in f-stops (powers of two).
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Only integer stops are allowed, for efficiency.
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.PP
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The
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.I \-r
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option invokes a reverse conversion, from a TIFF image to
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a RADIANCE picture.
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The RADIANCE picture file can be taken from the standard input
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or sent to the standard output by using a hyphen ('-') in place
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of the file name, but the TIFF image must be to or from a file.
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The
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.I \-x
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option can be used to specify an XYZE Radiance output file, rather
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than the default RGBE.
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.SH EXAMPLES
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To convert a Radiance picture to SGILOG-compressed TIFF format:
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.IP "" .2i
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ra_tiff \-L scene1.hdr scene1.tif
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.PP
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To later convert this image back into Radiance and display using
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human visibility tone-mapping:
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.IP "" .2i
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ra_tiff \-r scene1.tif scene1.hdr
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.br
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ximage \-e human scene1.hdr
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.SH AUTHOR
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Greg Ward Larson
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.br
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Sam Leffler
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.SH ACKNOWLEDGEMENT
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Work on this program was initiated and sponsored by the LESO
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group at EPFL in Switzerland.
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Additions for the SGILOG data encoding were sponsored by Silicon Graphics, Inc.
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.SH BUGS
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Many TIFF file subtypes are not supported.
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.br
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A gamma value other than 2.2 is not properly recorded or understood if
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recorded in the TIFF file.
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.SH "SEE ALSO"
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greg |
1.4 |
pfilt(1), ra_bmp(1), ra_bn(1), ra_ppm(1), ra_pr(1), ra_pr24(1), ra_t8(1),
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1.1 |
ra_t16(1), ximage(1)
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