man/man1/rcomb.1

.\" RCSid "$Id: rcomb.1,v 1.5 2024/01/17 21:50:15 greg Exp $"
.TH RCOMB 12/5/2023 RADIANCE
.SH NAME
rcomb - combine and convert matrices a row at a time
.SH SYNOPSIS
.B rcomb
[
.B \-h
][
.B \-w
][
.B \-f[afdc]
][
.B "\-f file"
][
.B "\-e expr"
][
.B "\-C {symbols|file}"
][
.B "\-c ce .."
][
.B "\-s sf .."
]
.B "m1 .."
[
.B "\-m mcat"
]
.SH DESCRIPTION
.I Rcomb
combines inputs given on the command line,
one matrix row or picture scanline at a time.
By default, the result is a linear combination of
the matrix elements or pixels transformed by
.I \-c
specifications and scaled by
.I \-s
coefficients, but an arbitrary mapping can be assigned with the
.I \-e
and
.I \-f
options, similar to the
.I pcomb(1)
and
.I rcalc(1)
commands.
(The definitions in each
.I \-f source
file are read and compiled from the RADIANCE library where it is found.)\0
.PP
If any
.I \-c
or
.I \-s
options follow the last input matrix, output results will be transformed
and/or scaled accordingly.
These operations are discussed in greater detail further on.
A single concatenation matrix may be applied after element operations
using the
.I \-m
option.
Matrix concatenation will happen before or after any trailing
operations, depending on relative command line placement.
.PP
Each input file must have a header containing the following metadata:
.sp
.nf
NROWS={number of rows}
NCOLS={number of columns}
NCOMP={number of components}
FORMAT={ascii|float|double|32-bit_rle_rgbe|32-bit_rle_xyze|Radiance_spectra}
.fi
.sp
The number of components indicates that each matrix element is actually
composed of multiple elements, most commonly an RGB triple.
This is essentially dividing the matrix into planes, where each component
participates in a separate calculation.
If an appropriate header is not present, it may be added with a call to
.I rcollate(1).
A matrix may be read from the standard input using a hyphen by itself ('-')
in the appropriate place on the command line.
Similarly, any of the inputs may be read from a command
instead of a file by
using quotes and a beginning exclamation point ('!').
.PP
In the case of Radiance picture files,
the number of columns is the X-dimension of the picture, and
the number of rows is the Y-dimension.
The picture must be in standard pixel ordering, and the zeroeth row
is at the top with the zeroeth column on the left.
Any exposure changes that were applied to the pictures before
.I rcomb
will be undone, similar to the
.I "pcomb \-o"
option.
Radiance spectral pictures with more than 3 components are also supported.
These are typically produced by
.I rtpict(1)
or
.I rfluxmtx(1).
.PP
Before each input, the
.I \-c
and/or
.I \-s
options may be used to modify the matrix elements.
The
.I \-c
option can "transform" the element values, possibly changing
the number of components in the matrix.
For example, a 3-component matrix can be transformed into a single-component
matrix by using
.I \-c
with three coefficients.
A four-component matrix can be turned into a two-component matrix using 8
coefficients, where the first four coefficients will be used to compute
the first new component, and the second four coefficients
yield the second new component.
Note that the number of coefficients must be an even multiple of the number
of original components.
.PP
Alternatively, a set of symbolic output components may be given to the
.I \-c
option, with the following definitions:
.sp
.nf
R       - red channel
G       - green channel
B       - blue channel
X       - CIE X channel
Y       - CIE Y channel (aka., luminance or illuminance)
Z       - CIE Z channel
S       - scotopic luminance or illuminance
M       - melanopic luminance or illuminance
A       - average component value
.fi
.sp
These letters may be given in any order as a single string, and if
.I "-c RGB"
or
.I "-c XYZ"
is specified for an input picture or the
.I "-fc"
option is given, the output will be written as a RGBE or XYZE picture.
Note that conversion from a float or RGBE color space applies a conversion
of 179 lumens/watt (for CIE or melanopic output) or 412 (for scotopic output),
and the reverse happens for conversion from XYZE input to RGB or RGBE output.
Lower case versions of all these components are also supported, the only
difference is that the aforementioned efficacy factors
will be left out of the conversion.
.PP
If a matrix or picture file path is given to the
.I \-c
option, then the color space of that file will be used, instead.
.PP
The
.I \-C
option takes either a symbolic color space or an input file, and will be
applied to all subsequent matrices that do not have their own associated
.I \-c
option.
.PP
Additionally, the
.I \-s
option applies the given scalar factor(s) to the elements of the matrix.
If only one factor is provided,
it will be used for all components.
If multiple factors are given, their number must match the number of matrix
components
.I after
application of any
.I \-c
option for this input matrix or picture, even if the
.I \-s
option appears first.
.PP
The number of components in all input
matrices after applying any
.I -c
transform must agree.
Similarly, the number of rows and columns of all results must match
exactly.
(The
.I rcrop(1)
utility may be used to trim inputs if necessary.)\0
.PP
If the
.I \-e
or
.I \-f
options are used to define a "co" variable or "co(p)" function,
this will be evaluated at each output
component for the current element.
The "co" variable defines identical operations for all components,
whereas "co(p)" may specify different operations for each component.
The element position is defined
by the "r" and "c" variables, where
.I r
goes from 0 to "nrows" minus one, and
.I c
goes from 0 to "ncols" minus one.
(Note that "nrows" may be zero if unspecified in inputs, and this
is a unique capability of
.I rcomb
to handle these.)\0
Component p from input i is accessed with the "ci(i,p)" function,
and the number of components is defined by the "ncomp" constant.
If given as "ci(i)", the function returns the current component
being evaluated by
.I rcomb.
A different component may be referenced using the second argument.
For example, "ci(1,2)" accesses
the second component from the first input.
If the input is a picture, the the constants "R", "G", and "B"
are conveniently defined as the channel numbers 1, 2, and 3,
respectively.
For color or spectral inputs, the function "wl(p)" gives the
central wavelength for channel
.I p
in nanometers.
For convenience and compatibility with
.I pcomb,
the functions "ri(i)", "gi(i)", and "bi(i)" are predefined as
"ci(i,R)", "ci(i,G)", and "ci(i,B)", respectively.
Accordingly, the "ro", "go", and "bo" 
variables may be used in place of "co(R)", "co(G)", and "co(B)",
but all three must be defined for this substitution to take place.
Finally, the total number of input files is set in the constant "nfiles".
.PP
Results are sent to the standard output.
By default, the values will be written in the lowest precision format
among the inputs, but the
.I \-f[adfc]
option may be used to explicitly output components
as ASCII (-fa), binary doubles (-fd), floats (-ff), or common-exponent
colors/spectra (-fc).
In the latter case, the actual matrix dimensions are written in the resolution string rather than the header.
Also, matrix results will be written as standard
Radiance pictures if they have either one
or three components.
In the one-component case, the output is written as grayscale.
If more than 3 components are in the final matrix and
.I -fc
is specified, the output will be a Radiance spectral picture.
.PP
The
.I \-h
option may be used to reduce the information header size, which
can grow disproportionately, otherwise.
The
.I \-w
option turns off warnings about divide-by-zero and other non-fatal
calculation errors.
.SH EXAMPLES
To convert two hyperspectral inputs to RGB color space,
average them together, and write them out as a RADIANCE picture:
.IP "" .2i
rcomb -C RGB -s .5 img1.spc -s .5 img2.spc > avg.hdr
.PP
Divide one set of matrix elements by the Euclidean sum of two others:
.IP "" .2i
rcomb -e "co=ci(1)/sqrt(ci(2)^2+ci(3)^2)" inp1.mtx 
inp2.mtx inp3.mtx > out.mtx
.PP
Compute the absolute and relative differences between melanopic and photopic values
in a spectral image:
.IP "" .2i
rcomb -fa -C MY -e "abs(x):if(x,x,-x)"
-e "co(p)=select(p,abs(ci(1,1)-ci(1,2)),(ci(1,1)-ci(1,2))/ci(1,2))"
input_spec.hsr > compare.mtx
.PP
Concatenate a spectral flux coefficient matrix with a spectral sky
matrix to compute a set of melanopic lux values:
.IP "" .2i
rcomb view_spec.mtx -m sky_spec.mtx -c M > melux.mtx
.SH NOTES
The
.I rcomb
tool was created to overcome some limitations of
.I rmtxop
and
.I pcomb,
whose capabilities somewhat overlap.
The former loads each matrix into memory before operations,
and element components take 8 bytes apiece, adding up quickly.
Very large matrices therefore present a problem with that tool.
Furthermore, 
.I rmtxop
does not allow arbitrary expressions, limiting
what can be accomplished easily on the command-line.
In contrast,
.I pcomb
is fully programmable and operates on its input using a
scanline window, so it can handle much larger input dimensions.
It also handles single- and three-component float matrices on
input and output, but unlike
.I rmtxop,
.I pcomb
has not been extended to handle RADIANCE hyperspectral images
or more general matrix data.
.PP
The
.I rcomb
tool is a compromise that exceeds the capabilities of either of
its predecessors in certain circumstances.
In particular, very large matrices may be combined using
arbitrary, user-defined operations, and the convenient
color conversions of
.I rmtxop
are supported for both input and output.
Finally, a single matrix may be concatenated after operations,
permitting a flux transfer matrix with millions of rows to
pass through.
Generally speaking,
.I rcomb
should be preferred over
.I rmtxop
for any operations in can handle, which is everything except
multiple matrix concatenations and transpose
operations, which are handled more efficiently by
.I rcollate(1)
in any case.
That said, there is no significant difference for
simple operations on smallish matrices, and note that only
.I rmtxop
and
.I dctimestep(1)
currently accept XML files as inputs.
Also, the resizing function of
.I pcomb
is not supported in
.I rcomb,
and should instead be handled by
.I pfilt(1).
.SH BUGS
The
.I rcomb
command currently ignores the "PRIMARIES" setting in input
headers, and does not produce any on output, even in
circumstances where it would make sense to.
.SH AUTHOR
Greg Ward
.SH "SEE ALSO"
dctimestep(1), icalc(1), getinfo(1), pcomb(1), pfilt(1),
ra_xyze(1), rcalc(1),
rcollate(1), rcontrib(1), rcrop(1), rfluxmtx(1), 
rmtxop(1), rtpict(1), rtrace(1), vwrays(1)
Revision:	1.6
Committed:	Sat Feb 10 19:32:32 2024 UTC (14 months, 3 weeks ago) by greg
Branch:	MAIN
Changes since 1.5:	+4 -3 lines
Log Message:	docs: typo fix plus clarification
#	Content
1	.\" RCSid "$Id: rcomb.1,v 1.5 2024/01/17 21:50:15 greg Exp $"
2	.TH RCOMB 12/5/2023 RADIANCE
3	.SH NAME
4	rcomb - combine and convert matrices a row at a time
5	.SH SYNOPSIS
6	.B rcomb
7	[
8	.B \-h
9	][
10	.B \-w
11	][
12	.B \-f[afdc]
13	][
14	.B "\-f file"
15	][
16	.B "\-e expr"
17	][
18	.B "\-C {symbols\|file}"
19	][
20	.B "\-c ce .."
21	][
22	.B "\-s sf .."
23	]
24	.B "m1 .."
25	[
26	.B "\-m mcat"
27	]
28	.SH DESCRIPTION
29	.I Rcomb
30	combines inputs given on the command line,
31	one matrix row or picture scanline at a time.
32	By default, the result is a linear combination of
33	the matrix elements or pixels transformed by
34	.I \-c
35	specifications and scaled by
36	.I \-s
37	coefficients, but an arbitrary mapping can be assigned with the
38	.I \-e
39	and
40	.I \-f
41	options, similar to the
42	.I pcomb(1)
43	and
44	.I rcalc(1)
45	commands.
46	(The definitions in each
47	.I \-f source
48	file are read and compiled from the RADIANCE library where it is found.)\0
49	.PP
50	If any
51	.I \-c
52	or
53	.I \-s
54	options follow the last input matrix, output results will be transformed
55	and/or scaled accordingly.
56	These operations are discussed in greater detail further on.
57	A single concatenation matrix may be applied after element operations
58	using the
59	.I \-m
60	option.
61	Matrix concatenation will happen before or after any trailing
62	operations, depending on relative command line placement.
63	.PP
64	Each input file must have a header containing the following metadata:
65	.sp
66	.nf
67	NROWS={number of rows}
68	NCOLS={number of columns}
69	NCOMP={number of components}
70	FORMAT={ascii\|float\|double\|32-bit_rle_rgbe\|32-bit_rle_xyze\|Radiance_spectra}
71	.fi
72	.sp
73	The number of components indicates that each matrix element is actually
74	composed of multiple elements, most commonly an RGB triple.
75	This is essentially dividing the matrix into planes, where each component
76	participates in a separate calculation.
77	If an appropriate header is not present, it may be added with a call to
78	.I rcollate(1).
79	A matrix may be read from the standard input using a hyphen by itself ('-')
80	in the appropriate place on the command line.
81	Similarly, any of the inputs may be read from a command
82	instead of a file by
83	using quotes and a beginning exclamation point ('!').
84	.PP
85	In the case of Radiance picture files,
86	the number of columns is the X-dimension of the picture, and
87	the number of rows is the Y-dimension.
88	The picture must be in standard pixel ordering, and the zeroeth row
89	is at the top with the zeroeth column on the left.
90	Any exposure changes that were applied to the pictures before
91	.I rcomb
92	will be undone, similar to the
93	.I "pcomb \-o"
94	option.
95	Radiance spectral pictures with more than 3 components are also supported.
96	These are typically produced by
97	.I rtpict(1)
98	or
99	.I rfluxmtx(1).
100	.PP
101	Before each input, the
102	.I \-c
103	and/or
104	.I \-s
105	options may be used to modify the matrix elements.
106	The
107	.I \-c
108	option can "transform" the element values, possibly changing
109	the number of components in the matrix.
110	For example, a 3-component matrix can be transformed into a single-component
111	matrix by using
112	.I \-c
113	with three coefficients.
114	A four-component matrix can be turned into a two-component matrix using 8
115	coefficients, where the first four coefficients will be used to compute
116	the first new component, and the second four coefficients
117	yield the second new component.
118	Note that the number of coefficients must be an even multiple of the number
119	of original components.
120	.PP
121	Alternatively, a set of symbolic output components may be given to the
122	.I \-c
123	option, with the following definitions:
124	.sp
125	.nf
126	R - red channel
127	G - green channel
128	B - blue channel
129	X - CIE X channel
130	Y - CIE Y channel (aka., luminance or illuminance)
131	Z - CIE Z channel
132	S - scotopic luminance or illuminance
133	M - melanopic luminance or illuminance
134	A - average component value
135	.fi
136	.sp
137	These letters may be given in any order as a single string, and if
138	.I "-c RGB"
139	or
140	.I "-c XYZ"
141	is specified for an input picture or the
142	.I "-fc"
143	option is given, the output will be written as a RGBE or XYZE picture.
144	Note that conversion from a float or RGBE color space applies a conversion
145	of 179 lumens/watt (for CIE or melanopic output) or 412 (for scotopic output),
146	and the reverse happens for conversion from XYZE input to RGB or RGBE output.
147	Lower case versions of all these components are also supported, the only
148	difference is that the aforementioned efficacy factors
149	will be left out of the conversion.
150	.PP
151	If a matrix or picture file path is given to the
152	.I \-c
153	option, then the color space of that file will be used, instead.
154	.PP
155	The
156	.I \-C
157	option takes either a symbolic color space or an input file, and will be
158	applied to all subsequent matrices that do not have their own associated
159	.I \-c
160	option.
161	.PP
162	Additionally, the
163	.I \-s
164	option applies the given scalar factor(s) to the elements of the matrix.
165	If only one factor is provided,
166	it will be used for all components.
167	If multiple factors are given, their number must match the number of matrix
168	components
169	.I after
170	application of any
171	.I \-c
172	option for this input matrix or picture, even if the
173	.I \-s
174	option appears first.
175	.PP
176	The number of components in all input
177	matrices after applying any
178	.I -c
179	transform must agree.
180	Similarly, the number of rows and columns of all results must match
181	exactly.
182	(The
183	.I rcrop(1)
184	utility may be used to trim inputs if necessary.)\0
185	.PP
186	If the
187	.I \-e
188	or
189	.I \-f
190	options are used to define a "co" variable or "co(p)" function,
191	this will be evaluated at each output
192	component for the current element.
193	The "co" variable defines identical operations for all components,
194	whereas "co(p)" may specify different operations for each component.
195	The element position is defined
196	by the "r" and "c" variables, where
197	.I r
198	goes from 0 to "nrows" minus one, and
199	.I c
200	goes from 0 to "ncols" minus one.
201	(Note that "nrows" may be zero if unspecified in inputs, and this
202	is a unique capability of
203	.I rcomb
204	to handle these.)\0
205	Component p from input i is accessed with the "ci(i,p)" function,
206	and the number of components is defined by the "ncomp" constant.
207	If given as "ci(i)", the function returns the current component
208	being evaluated by
209	.I rcomb.
210	A different component may be referenced using the second argument.
211	For example, "ci(1,2)" accesses
212	the second component from the first input.
213	If the input is a picture, the the constants "R", "G", and "B"
214	are conveniently defined as the channel numbers 1, 2, and 3,
215	respectively.
216	For color or spectral inputs, the function "wl(p)" gives the
217	central wavelength for channel
218	.I p
219	in nanometers.
220	For convenience and compatibility with
221	.I pcomb,
222	the functions "ri(i)", "gi(i)", and "bi(i)" are predefined as
223	"ci(i,R)", "ci(i,G)", and "ci(i,B)", respectively.
224	Accordingly, the "ro", "go", and "bo"
225	variables may be used in place of "co(R)", "co(G)", and "co(B)",
226	but all three must be defined for this substitution to take place.
227	Finally, the total number of input files is set in the constant "nfiles".
228	.PP
229	Results are sent to the standard output.
230	By default, the values will be written in the lowest precision format
231	among the inputs, but the
232	.I \-f[adfc]
233	option may be used to explicitly output components
234	as ASCII (-fa), binary doubles (-fd), floats (-ff), or common-exponent
235	colors/spectra (-fc).
236	In the latter case, the actual matrix dimensions are written in the resolution string rather than the header.
237	Also, matrix results will be written as standard
238	Radiance pictures if they have either one
239	or three components.
240	In the one-component case, the output is written as grayscale.
241	If more than 3 components are in the final matrix and
242	.I -fc
243	is specified, the output will be a Radiance spectral picture.
244	.PP
245	The
246	.I \-h
247	option may be used to reduce the information header size, which
248	can grow disproportionately, otherwise.
249	The
250	.I \-w
251	option turns off warnings about divide-by-zero and other non-fatal
252	calculation errors.
253	.SH EXAMPLES
254	To convert two hyperspectral inputs to RGB color space,
255	average them together, and write them out as a RADIANCE picture:
256	.IP "" .2i
257	rcomb -C RGB -s .5 img1.spc -s .5 img2.spc > avg.hdr
258	.PP
259	Divide one set of matrix elements by the Euclidean sum of two others:
260	.IP "" .2i
261	rcomb -e "co=ci(1)/sqrt(ci(2)^2+ci(3)^2)" inp1.mtx
262	inp2.mtx inp3.mtx > out.mtx
263	.PP
264	Compute the absolute and relative differences between melanopic and photopic values
265	in a spectral image:
266	.IP "" .2i
267	rcomb -fa -C MY -e "abs(x):if(x,x,-x)"
268	-e "co(p)=select(p,abs(ci(1,1)-ci(1,2)),(ci(1,1)-ci(1,2))/ci(1,2))"
269	input_spec.hsr > compare.mtx
270	.PP
271	Concatenate a spectral flux coefficient matrix with a spectral sky
272	matrix to compute a set of melanopic lux values:
273	.IP "" .2i
274	rcomb view_spec.mtx -m sky_spec.mtx -c M > melux.mtx
275	.SH NOTES
276	The
277	.I rcomb
278	tool was created to overcome some limitations of
279	.I rmtxop
280	and
281	.I pcomb,
282	whose capabilities somewhat overlap.
283	The former loads each matrix into memory before operations,
284	and element components take 8 bytes apiece, adding up quickly.
285	Very large matrices therefore present a problem with that tool.
286	Furthermore,
287	.I rmtxop
288	does not allow arbitrary expressions, limiting
289	what can be accomplished easily on the command-line.
290	In contrast,
291	.I pcomb
292	is fully programmable and operates on its input using a
293	scanline window, so it can handle much larger input dimensions.
294	It also handles single- and three-component float matrices on
295	input and output, but unlike
296	.I rmtxop,
297	.I pcomb
298	has not been extended to handle RADIANCE hyperspectral images
299	or more general matrix data.
300	.PP
301	The
302	.I rcomb
303	tool is a compromise that exceeds the capabilities of either of
304	its predecessors in certain circumstances.
305	In particular, very large matrices may be combined using
306	arbitrary, user-defined operations, and the convenient
307	color conversions of
308	.I rmtxop
309	are supported for both input and output.
310	Finally, a single matrix may be concatenated after operations,
311	permitting a flux transfer matrix with millions of rows to
312	pass through.
313	Generally speaking,
314	.I rcomb
315	should be preferred over
316	.I rmtxop
317	for any operations in can handle, which is everything except
318	multiple matrix concatenations and transpose
319	operations, which are handled more efficiently by
320	.I rcollate(1)
321	in any case.
322	That said, there is no significant difference for
323	simple operations on smallish matrices, and note that only
324	.I rmtxop
325	and
326	.I dctimestep(1)
327	currently accept XML files as inputs.
328	Also, the resizing function of
329	.I pcomb
330	is not supported in
331	.I rcomb,
332	and should instead be handled by
333	.I pfilt(1).
334	.SH BUGS
335	The
336	.I rcomb
337	command currently ignores the "PRIMARIES" setting in input
338	headers, and does not produce any on output, even in
339	circumstances where it would make sense to.
340	.SH AUTHOR
341	Greg Ward
342	.SH "SEE ALSO"
343	dctimestep(1), icalc(1), getinfo(1), pcomb(1), pfilt(1),
344	ra_xyze(1), rcalc(1),
345	rcollate(1), rcontrib(1), rcrop(1), rfluxmtx(1),
346	rmtxop(1), rtpict(1), rtrace(1), vwrays(1)