1 |
.\" RCSid "$Id$" |
2 |
.TH RA_XYZE 1 5/30/96 RADIANCE |
3 |
.SH NAME |
4 |
ra_xyze - convert between RADIANCE RGBE and XYZE formats |
5 |
.SH SYNOPSIS |
6 |
.B ra_xyze |
7 |
[ |
8 |
.B \-r |
9 |
][ |
10 |
.B "\-e exposure" |
11 |
][ |
12 |
.B \-c |
13 |
| |
14 |
.B \-u |
15 |
][ |
16 |
.B "\-p xr yr xg yg xb yb xw yw" |
17 |
] |
18 |
[ |
19 |
.B input |
20 |
[ |
21 |
.B output |
22 |
] |
23 |
] |
24 |
.SH DESCRIPTION |
25 |
.I Ra_xyze |
26 |
converts between RADIANCE RGBE (red,green,blue,exponent) and XYZE |
27 |
(CIE X,Y,Z,exponent) formats. |
28 |
The |
29 |
.I \-e |
30 |
option specifies an exposure compensation, which may be given as |
31 |
a decimal multiplier or in f-stops (powers of two). |
32 |
By default, |
33 |
.I ra_xyze |
34 |
produces a flat XYZE RADIANCE picture file from any type of RADIANCE |
35 |
input picture. |
36 |
To override these defaults, the |
37 |
.I \-c |
38 |
option may be used to specify run-length encoded output, |
39 |
or the |
40 |
.I \-u |
41 |
option may be used to specify a flat output. |
42 |
.PP |
43 |
The |
44 |
.I \-r |
45 |
option causes |
46 |
.I ra_xyze |
47 |
to produce a run-length encoded RGBE file instead. |
48 |
The |
49 |
.I \-p |
50 |
option may be used to override the standard RADIANCE RGB primary |
51 |
colors to tailor the image for a particular output device or |
52 |
representation. |
53 |
The eight floating-point arguments to this option are the 1931 |
54 |
CIE (x,y) chromaticity coordinates of the three RGB primaries |
55 |
plus the white point, in that order. |
56 |
The new primaries will be recorded in the header of the output file, |
57 |
so that the original information may be fully recovered later. |
58 |
It is not necessary that the input file by in XYZE format. |
59 |
Th |
60 |
.I \-r |
61 |
option may therefore be used to convert from one RGB primary |
62 |
representation to another using the |
63 |
.I \-p |
64 |
option. |
65 |
.PP |
66 |
If the output file is missing, the standard output is used. |
67 |
If the input file is missing as well, the standard input is used. |
68 |
.SH NOTES |
69 |
The CIE standard used is the 1931 2-degree observer, and the |
70 |
correct output representation relies on the original RADIANCE |
71 |
input description being defined properly in terms of the standard |
72 |
RADIANCE RGB primaries, whose CIE (x,y) chromaticity values are |
73 |
defined in the header file in src/common/color.h. |
74 |
In this same file is a standard for the luminous efficacy of white |
75 |
light (WHTEFFICACY), which is used as a conversion between lumens |
76 |
and watts throughout RADIANCE. |
77 |
This same factor is applied by |
78 |
.I ra_xyze |
79 |
when converting between the radiometric units of the RGBE format |
80 |
and the photometric units of the XYZE format. |
81 |
The purpose of this factor is to ensure that the Y component of |
82 |
the CIE representation is luminance in units of candelas/meter^2. |
83 |
.PP |
84 |
Most of the RADIANCE picture filters should work uniformly on either |
85 |
RGBE or XYZE files, so it is not necessary to convert back to RGBE |
86 |
format except for conversion or display, in which case the correct |
87 |
primaries for the chosen output device should be specified with the |
88 |
.I \-p |
89 |
option if they are known. |
90 |
.SH EXAMPLES |
91 |
To convert RGBE output from |
92 |
.I rpict(1) |
93 |
into run-length encoded XYZE format: |
94 |
.IP "" .2i |
95 |
rpict [options] scene.oct | ra_xyze -c > scene_xyz.pic |
96 |
.PP |
97 |
To prepare a RADIANCE picture for display on a calibrated NTSC monitor: |
98 |
.IP "" .2i |
99 |
ra_xyze -r -p .670 .330 .210 .710 .140 .080 .333 .333 stand.pic ntsc.pic |
100 |
.SH AUTHOR |
101 |
Greg Ward |
102 |
.SH BUGS |
103 |
Any color correction applied to the original image is not removed |
104 |
or translated by |
105 |
.I ra_xyze, |
106 |
and it may result in color shifts in the output. |
107 |
If color preservation is important and the correction is unwanted, |
108 |
it is best to remove it with |
109 |
.I pfilt(1) |
110 |
using the |
111 |
.I \-er, |
112 |
.I \-eg |
113 |
and |
114 |
.I \-eb |
115 |
options first. |
116 |
(Simply look at the header and apply the reciprocal primaries of all |
117 |
COLORCORR= lines multiplied together.) |
118 |
Better still, get the picture before color correction is applied. |
119 |
.SH "SEE ALSO" |
120 |
pfilt(1), ra_rgbe(1), rpict(1) |