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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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If the Radiance input is a hyperspectral picture, it will be |
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converted accurately if the output is anything but 24-bit RGB. |
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In the latter case, the converted colors will be approximate. |
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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 |
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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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pfilt(1), ra_bmp(1), ra_bn(1), ra_ppm(1), ra_pr(1), ra_pr24(1), ra_t8(1), |
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ra_t16(1), ximage(1) |
