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.\" RCSid "$Id" |
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.TH RA_PPM 1 2/10/99 RADIANCE |
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.SH NAME |
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ra_ppm - convert RADIANCE picture to/from a Poskanzer Portable Pixmap |
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.SH SYNOPSIS |
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.B ra_ppm |
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[ |
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.B \-r |
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][ |
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.B \-a |
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][ |
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.B \-b |
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][ |
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.B "\-s maxv" |
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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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[ |
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.B input |
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[ |
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.B output |
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] |
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] |
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.SH DESCRIPTION |
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.I Ra_ppm |
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converts between RADIANCE and Poskanzer Portable Pixmap 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. |
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An exponent of 1 turns gamma correction off. |
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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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The |
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.I \-r |
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option invokes a reverse conversion, from a Pixmap to |
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a RADIANCE picture. |
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If the output file is missing, the standard output is used. |
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If the input file is missing as well, the standard input is used. |
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.PP |
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The |
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.I \-a |
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option produces a standard ASCII Pixmap representation instead of |
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the default binary file. |
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The file is much larger and the conversion is much slower, which is |
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why this format is not normally used. |
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The |
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.I \-b |
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option forces greyscale output. |
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The |
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.I \-s |
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option controls the output scale, which is 255 by default. |
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If this value is set above 255, then two bytes will be output for each |
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component in binary mode. |
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This may not be understood by some PPM readers, which do not understand |
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files with maximum values greater than 255. |
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The maximum allowed setting for this parameter is 65535. |
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.PP |
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With the |
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.I \-r |
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option, the type of the Pixmap input file is determined automatically. |
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.I Ra_ppm |
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will read either greyscale or color Pixmaps, with any precision up |
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to a maximum scale of 65535. |
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.SH NOTES |
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The Poskanzer Portable Bitmap Plus package contains translators between the |
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Pixmap format and many of the dozen or so image |
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file "standards" that exist. |
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At the time of this writing, the software is free and available by |
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anonymous ftp from export.lcs.mit.edu (18.30.0.238) in the file |
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"contrib/pbmplus.tar.Z". |
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.SH AUTHOR |
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Greg Ward |
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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 and Silicon Graphics, Inc. |
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.SH "SEE ALSO" |
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pfilt(1), ra_bn(1), ra_pr(1), ra_pr24(1), ra_t8(1), ra_t16(1), |
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ra_tiff(1), ximage(1) |
