man/man1/rcomb.1

.\" RCSid "$Id: rcomb.1,v 1.10 2024/06/28 21:04:49 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 "\-n nproc"
][
.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 below.
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 channels, 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 an efficacy factor
of 179 lumens/watt (for CIE or melanopic output) or 412 (for scotopic output),
and the inverse happens for conversion from XYZE input to RGB or RGBE output.
Lower case versions of all these components are also supported, the only
difference being that the efficacy factors are ignored.
.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,
which will be evaluated for each output
component from 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.
.PP
The
.I \-n
option specifies how many execution processes to employ,
which may improve performance on multi-core architectures,
especially for matrix multiplication
and complex operations on long input rows.
.SH EXAMPLES
To convert two hyperspectral pictures to RGB color space,
average them together, and write them out as a RADIANCE picture:
.IP "" .2i
rcomb -C RGB -s .5 img1.hsr -s .5 -fc img2.hsr > 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 -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 -fa > 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 are stored as double-precision.
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 it can handle, which is everything except
multiple matrix concatenations and transpose
operations.
The latter may be handled more efficiently by
.I rcollate(1).
That said, there is no significant difference for
simple operations on small matrices, and only
.I rmtxop
and
.I dctimestep(1)
accept XML files as inputs.
Also note that 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_rgbe(1), ra_xyze(1), rcalc(1),
rcollate(1), rcontrib(1), rcrop(1), rfluxmtx(1), 
rmtxop(1), rtpict(1), rtrace(1), vwrays(1)
Revision:	1.11
Committed:	Tue Oct 1 01:16:26 2024 UTC (7 months ago) by greg
Branch:	MAIN
Changes since 1.10:	+2 -2 lines
Log Message:	feat(ra_xyze): added accurate conversion of hyperspectral pictures on input
#	User	Rev	Content
1	greg	1.11	.\" RCSid "$Id: rcomb.1,v 1.10 2024/06/28 21:04:49 greg Exp $"
2	greg	1.1	.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	greg	1.8	.B "\-n nproc"
15			][
16	greg	1.1	.B "\-f file"
17			][
18			.B "\-e expr"
19			][
20			.B "\-C {symbols\|file}"
21			][
22			.B "\-c ce .."
23			][
24			.B "\-s sf .."
25			]
26			.B "m1 .."
27			[
28			.B "\-m mcat"
29			]
30			.SH DESCRIPTION
31			.I Rcomb
32			combines inputs given on the command line,
33			one matrix row or picture scanline at a time.
34			By default, the result is a linear combination of
35			the matrix elements or pixels transformed by
36			.I \-c
37			specifications and scaled by
38			.I \-s
39			coefficients, but an arbitrary mapping can be assigned with the
40			.I \-e
41			and
42			.I \-f
43			options, similar to the
44			.I pcomb(1)
45			and
46			.I rcalc(1)
47			commands.
48			(The definitions in each
49			.I \-f source
50			file are read and compiled from the RADIANCE library where it is found.)\0
51			.PP
52			If any
53			.I \-c
54			or
55			.I \-s
56			options follow the last input matrix, output results will be transformed
57			and/or scaled accordingly.
58	greg	1.7	These operations are discussed in greater detail below.
59	greg	1.1	A single concatenation matrix may be applied after element operations
60			using the
61			.I \-m
62			option.
63			Matrix concatenation will happen before or after any trailing
64			operations, depending on relative command line placement.
65			.PP
66			Each input file must have a header containing the following metadata:
67			.sp
68			.nf
69			NROWS={number of rows}
70			NCOLS={number of columns}
71			NCOMP={number of components}
72			FORMAT={ascii\|float\|double\|32-bit_rle_rgbe\|32-bit_rle_xyze\|Radiance_spectra}
73			.fi
74			.sp
75			The number of components indicates that each matrix element is actually
76	greg	1.7	composed of multiple channels, most commonly an RGB triple.
77	greg	1.1	This is essentially dividing the matrix into planes, where each component
78			participates in a separate calculation.
79			If an appropriate header is not present, it may be added with a call to
80			.I rcollate(1).
81			A matrix may be read from the standard input using a hyphen by itself ('-')
82			in the appropriate place on the command line.
83			Similarly, any of the inputs may be read from a command
84			instead of a file by
85			using quotes and a beginning exclamation point ('!').
86			.PP
87			In the case of Radiance picture files,
88			the number of columns is the X-dimension of the picture, and
89			the number of rows is the Y-dimension.
90			The picture must be in standard pixel ordering, and the zeroeth row
91			is at the top with the zeroeth column on the left.
92			Any exposure changes that were applied to the pictures before
93			.I rcomb
94			will be undone, similar to the
95			.I "pcomb \-o"
96			option.
97			Radiance spectral pictures with more than 3 components are also supported.
98			These are typically produced by
99	greg	1.5	.I rtpict(1)
100	greg	1.1	or
101			.I rfluxmtx(1).
102			.PP
103			Before each input, the
104			.I \-c
105			and/or
106			.I \-s
107			options may be used to modify the matrix elements.
108			The
109			.I \-c
110			option can "transform" the element values, possibly changing
111			the number of components in the matrix.
112			For example, a 3-component matrix can be transformed into a single-component
113			matrix by using
114			.I \-c
115			with three coefficients.
116			A four-component matrix can be turned into a two-component matrix using 8
117			coefficients, where the first four coefficients will be used to compute
118			the first new component, and the second four coefficients
119			yield the second new component.
120			Note that the number of coefficients must be an even multiple of the number
121			of original components.
122			.PP
123			Alternatively, a set of symbolic output components may be given to the
124			.I \-c
125			option, with the following definitions:
126			.sp
127			.nf
128			R - red channel
129			G - green channel
130			B - blue channel
131			X - CIE X channel
132			Y - CIE Y channel (aka., luminance or illuminance)
133			Z - CIE Z channel
134			S - scotopic luminance or illuminance
135			M - melanopic luminance or illuminance
136			A - average component value
137			.fi
138			.sp
139			These letters may be given in any order as a single string, and if
140			.I "-c RGB"
141			or
142			.I "-c XYZ"
143			is specified for an input picture or the
144			.I "-fc"
145			option is given, the output will be written as a RGBE or XYZE picture.
146	greg	1.9	Note that conversion from a float or RGBE color space applies an efficacy factor
147	greg	1.1	of 179 lumens/watt (for CIE or melanopic output) or 412 (for scotopic output),
148	greg	1.9	and the inverse happens for conversion from XYZE input to RGB or RGBE output.
149	greg	1.3	Lower case versions of all these components are also supported, the only
150	greg	1.9	difference being that the efficacy factors are ignored.
151	greg	1.1	.PP
152			If a matrix or picture file path is given to the
153			.I \-c
154			option, then the color space of that file will be used, instead.
155			.PP
156			The
157			.I \-C
158			option takes either a symbolic color space or an input file, and will be
159			applied to all subsequent matrices that do not have their own associated
160			.I \-c
161			option.
162			.PP
163			Additionally, the
164			.I \-s
165			option applies the given scalar factor(s) to the elements of the matrix.
166			If only one factor is provided,
167			it will be used for all components.
168			If multiple factors are given, their number must match the number of matrix
169			components
170			.I after
171			application of any
172			.I \-c
173			option for this input matrix or picture, even if the
174			.I \-s
175			option appears first.
176			.PP
177			The number of components in all input
178			matrices after applying any
179			.I -c
180			transform must agree.
181			Similarly, the number of rows and columns of all results must match
182			exactly.
183			(The
184			.I rcrop(1)
185			utility may be used to trim inputs if necessary.)\0
186			.PP
187			If the
188			.I \-e
189			or
190			.I \-f
191			options are used to define a "co" variable or "co(p)" function,
192	greg	1.7	which will be evaluated for each output
193			component from the current element.
194	greg	1.1	The "co" variable defines identical operations for all components,
195			whereas "co(p)" may specify different operations for each component.
196			The element position is defined
197			by the "r" and "c" variables, where
198			.I r
199			goes from 0 to "nrows" minus one, and
200			.I c
201			goes from 0 to "ncols" minus one.
202	greg	1.2	(Note that "nrows" may be zero if unspecified in inputs, and this
203			is a unique capability of
204			.I rcomb
205			to handle these.)\0
206	greg	1.1	Component p from input i is accessed with the "ci(i,p)" function,
207			and the number of components is defined by the "ncomp" constant.
208			If given as "ci(i)", the function returns the current component
209			being evaluated by
210			.I rcomb.
211	greg	1.6	A different component may be referenced using the second argument.
212	greg	1.1	For example, "ci(1,2)" accesses
213			the second component from the first input.
214			If the input is a picture, the the constants "R", "G", and "B"
215			are conveniently defined as the channel numbers 1, 2, and 3,
216			respectively.
217			For color or spectral inputs, the function "wl(p)" gives the
218			central wavelength for channel
219			.I p
220			in nanometers.
221			For convenience and compatibility with
222			.I pcomb,
223			the functions "ri(i)", "gi(i)", and "bi(i)" are predefined as
224			"ci(i,R)", "ci(i,G)", and "ci(i,B)", respectively.
225			Accordingly, the "ro", "go", and "bo"
226	greg	1.6	variables may be used in place of "co(R)", "co(G)", and "co(B)",
227			but all three must be defined for this substitution to take place.
228	greg	1.1	Finally, the total number of input files is set in the constant "nfiles".
229			.PP
230			Results are sent to the standard output.
231			By default, the values will be written in the lowest precision format
232			among the inputs, but the
233			.I \-f[adfc]
234			option may be used to explicitly output components
235			as ASCII (-fa), binary doubles (-fd), floats (-ff), or common-exponent
236			colors/spectra (-fc).
237			In the latter case, the actual matrix dimensions are written in the resolution string rather than the header.
238			Also, matrix results will be written as standard
239			Radiance pictures if they have either one
240			or three components.
241			In the one-component case, the output is written as grayscale.
242			If more than 3 components are in the final matrix and
243			.I -fc
244			is specified, the output will be a Radiance spectral picture.
245			.PP
246			The
247			.I \-h
248			option may be used to reduce the information header size, which
249			can grow disproportionately, otherwise.
250			The
251			.I \-w
252			option turns off warnings about divide-by-zero and other non-fatal
253			calculation errors.
254	greg	1.8	.PP
255			The
256			.I \-n
257			option specifies how many execution processes to employ,
258			which may improve performance on multi-core architectures,
259			especially for matrix multiplication
260			and complex operations on long input rows.
261	greg	1.1	.SH EXAMPLES
262	greg	1.10	To convert two hyperspectral pictures to RGB color space,
263	greg	1.1	average them together, and write them out as a RADIANCE picture:
264			.IP "" .2i
265	greg	1.10	rcomb -C RGB -s .5 img1.hsr -s .5 -fc img2.hsr > avg.hdr
266	greg	1.1	.PP
267			Divide one set of matrix elements by the Euclidean sum of two others:
268			.IP "" .2i
269			rcomb -e "co=ci(1)/sqrt(ci(2)^2+ci(3)^2)" inp1.mtx
270			inp2.mtx inp3.mtx > out.mtx
271			.PP
272			Compute the absolute and relative differences between melanopic and photopic values
273			in a spectral image:
274			.IP "" .2i
275	greg	1.10	rcomb -C MY -e "abs(x):if(x,x,-x)"
276	greg	1.1	-e "co(p)=select(p,abs(ci(1,1)-ci(1,2)),(ci(1,1)-ci(1,2))/ci(1,2))"
277	greg	1.10	input_spec.hsr -fa > compare.mtx
278	greg	1.1	.PP
279			Concatenate a spectral flux coefficient matrix with a spectral sky
280			matrix to compute a set of melanopic lux values:
281			.IP "" .2i
282			rcomb view_spec.mtx -m sky_spec.mtx -c M > melux.mtx
283			.SH NOTES
284			The
285			.I rcomb
286			tool was created to overcome some limitations of
287			.I rmtxop
288			and
289			.I pcomb,
290			whose capabilities somewhat overlap.
291			The former loads each matrix into memory before operations,
292	greg	1.7	and element components are stored as double-precision.
293	greg	1.1	Very large matrices therefore present a problem with that tool.
294			Furthermore,
295			.I rmtxop
296			does not allow arbitrary expressions, limiting
297			what can be accomplished easily on the command-line.
298			In contrast,
299			.I pcomb
300			is fully programmable and operates on its input using a
301			scanline window, so it can handle much larger input dimensions.
302			It also handles single- and three-component float matrices on
303			input and output, but unlike
304			.I rmtxop,
305			.I pcomb
306			has not been extended to handle RADIANCE hyperspectral images
307			or more general matrix data.
308			.PP
309			The
310			.I rcomb
311			tool is a compromise that exceeds the capabilities of either of
312			its predecessors in certain circumstances.
313			In particular, very large matrices may be combined using
314			arbitrary, user-defined operations, and the convenient
315			color conversions of
316			.I rmtxop
317			are supported for both input and output.
318			Finally, a single matrix may be concatenated after operations,
319			permitting a flux transfer matrix with millions of rows to
320			pass through.
321			Generally speaking,
322			.I rcomb
323			should be preferred over
324			.I rmtxop
325	greg	1.7	for any operations it can handle, which is everything except
326	greg	1.1	multiple matrix concatenations and transpose
327	greg	1.7	operations.
328			The latter may be handled more efficiently by
329			.I rcollate(1).
330	greg	1.1	That said, there is no significant difference for
331	greg	1.7	simple operations on small matrices, and only
332	greg	1.1	.I rmtxop
333			and
334			.I dctimestep(1)
335	greg	1.7	accept XML files as inputs.
336			Also note that the resizing function of
337	greg	1.1	.I pcomb
338			is not supported in
339			.I rcomb,
340			and should instead be handled by
341			.I pfilt(1).
342	greg	1.4	.SH BUGS
343			The
344			.I rcomb
345			command currently ignores the "PRIMARIES" setting in input
346			headers, and does not produce any on output, even in
347			circumstances where it would make sense to.
348	greg	1.1	.SH AUTHOR
349			Greg Ward
350			.SH "SEE ALSO"
351			dctimestep(1), icalc(1), getinfo(1), pcomb(1), pfilt(1),
352	greg	1.11	ra_rgbe(1), ra_xyze(1), rcalc(1),
353	greg	1.1	rcollate(1), rcontrib(1), rcrop(1), rfluxmtx(1),
354			rmtxop(1), rtpict(1), rtrace(1), vwrays(1)