1 |
.\" RCSid "$Id$" |
2 |
.TH RA_PPM 1 2/10/99 RADIANCE |
3 |
.SH NAME |
4 |
ra_ppm - convert RADIANCE picture to/from a Poskanzer Portable Pixmap |
5 |
.SH SYNOPSIS |
6 |
.B ra_ppm |
7 |
[ |
8 |
.B \-r |
9 |
][ |
10 |
.B \-a |
11 |
][ |
12 |
.B \-b |
13 |
][ |
14 |
.B "\-s maxv" |
15 |
][ |
16 |
.B "\-g gamma" |
17 |
][ |
18 |
.B "\-e +/-stops" |
19 |
] |
20 |
[ |
21 |
.B input |
22 |
[ |
23 |
.B output |
24 |
] |
25 |
] |
26 |
.SH DESCRIPTION |
27 |
.I Ra_ppm |
28 |
converts between RADIANCE and Poskanzer Portable Pixmap formats. |
29 |
The |
30 |
.I \-g |
31 |
option specifies the exponent used in gamma correction; |
32 |
the default value is 2.2. |
33 |
An exponent of 1 turns gamma correction off. |
34 |
The |
35 |
.I \-e |
36 |
option specifies an exposure compensation in f-stops (powers of two). |
37 |
Only integer stops are allowed, for efficiency. |
38 |
The |
39 |
.I \-r |
40 |
option invokes a reverse conversion, from a Pixmap to |
41 |
a RADIANCE picture. |
42 |
If the output file is missing, the standard output is used. |
43 |
If the input file is missing as well, the standard input is used. |
44 |
.PP |
45 |
The |
46 |
.I \-a |
47 |
option produces a standard ASCII Pixmap representation instead of |
48 |
the default binary file. |
49 |
The file is much larger and the conversion is much slower, which is |
50 |
why this format is not normally used. |
51 |
The |
52 |
.I \-b |
53 |
option forces greyscale output. |
54 |
The |
55 |
.I \-s |
56 |
option controls the output scale, which is 255 by default. |
57 |
If this value is set above 255, then two bytes will be output for each |
58 |
component in binary mode. |
59 |
This may not be understood by some PPM readers, which do not understand |
60 |
files with maximum values greater than 255. |
61 |
The maximum allowed setting for this parameter is 65535. |
62 |
.PP |
63 |
With the |
64 |
.I \-r |
65 |
option, the type of the Pixmap input file is determined automatically. |
66 |
.I Ra_ppm |
67 |
will read either greyscale or color Pixmaps, with any precision up |
68 |
to a maximum scale of 65535. |
69 |
.SH NOTES |
70 |
The Poskanzer Portable Bitmap Plus package contains translators between the |
71 |
Pixmap format and many of the dozen or so image |
72 |
file "standards" that exist. |
73 |
At the time of this writing, the software is free and available by |
74 |
anonymous ftp from export.lcs.mit.edu (18.30.0.238) in the file |
75 |
"contrib/pbmplus.tar.Z". |
76 |
.SH AUTHOR |
77 |
Greg Ward |
78 |
.SH ACKNOWLEDGEMENT |
79 |
Work on this program was initiated and sponsored by the LESO |
80 |
group at EPFL in Switzerland and Silicon Graphics, Inc. |
81 |
.SH "SEE ALSO" |
82 |
pfilt(1), ra_bn(1), ra_pr(1), ra_pr24(1), ra_t8(1), ra_t16(1), |
83 |
ra_tiff(1), ximage(1) |