profile/colverify
Summary
Verify a color transform by comparing CIE measurement values from
two test charts. The charts can be any suitably formatted CGATS or .ti3 format that contains
corresponding XYZ, Lab or spectral values. The overall average and
worst case delta E will be reported, as well as the worst 10% and
best 90% of values.
Usage Summary
colverify [-options] target.ti3 measured.ti3
-v
[n]
Verbose mode, n >= 2 print each value
-n
Normalise
each files reading to white Y
-N
Normalise
each files reading to white XYZ
-D
Use
D50 100.0 as L*a*b* white reference
-c
Show CIE94 delta E values
-k
Show CIEDE2000 delta E values
-s
Sort patch value by error
-w
create VRML vector visualisation (measured.wrl)
-W
create VRML marker & vector visualisation
(measured.wrl)
-x
Use VRML axes
-f
[illum] Use Fluorescent
Whitening Agent compensation [opt. simulated inst. illum.:
M0, M1, M2, A, C, D50 (def.), D50M2, D65, F5, F8, F10 or
file.sp]
-i illum
Choose illuminant for computation of CIE XYZ from spectral
data & FWA:
A, C, D50 (def.), D50M2, D65, F5, F8, F10 or file.sp
-o observ Choose
CIE Observer for spectral data:
1931_2 (def.), 1964_10, S&B
1955_2, shaw, J&V 1978_2
-L profile.icm Skip any first file out of
profile gamut patches
-X file.ccmx Apply Colorimeter
Correction Matrix to second file
target.ti3
Target or reference patch data file
measured.ti3 Measured or actual patch
data file
Usage Details and Discussion
colverify provides a way of verifying how well a color
transformation (such a proofing) performs.
The -v flag prints out extra information during the
checking, and prints each patch value, rather than just a summary.
The -n flag causes the two sets of values to be normalized
to the Y value of white for each set before comparison. White is
assumed to be the patch with the largest Y value.
The -N flag causes the two sets of values to be normalized
to the XYZ of white for each set before comparison. White is assumed
to be the patch with the largest Y value.
The -D flag causes the white reference point for the
conversion to L*a*b* to be D50 with a Y value of 100%. By default
the sample with the largest Y value is found, and the L*a*b* white
reference scaled to have that Y value. This allows sensible delta E
values when comparing absolute color values, such as those from
emission or display measurements.
The -c option causes the differences between the test values
and the profile prediction of the color for each device value to be
displayed in CIE94 delta E, rather than plain L*a*b* delta E. CIE94
delta E has a closer correspondence with perceived color differences
than the default CIE76 delta E values.
The -k option causes the differences between the test values
and the profile prediction of the color for each device value to be
displayed in CIEDE2000 delta E, rather than plain L*a*b* delta E.
CIEDE2000 delta E has a closer correspondence with perceived color
differences than either CIE76 or CIE94 delta E values.
If the -s flag is used in combination with the -v
flag, then the test point by test point output will be sorted from
worst to best.
The -w creates a VRML
3D visualization of the differences between the test points in D50
L*a*b* space, each difference being shown as a line vector. If the -W flag is used, then the target
and measured values will also be marked by a small sphere. This can
be used to visualize the placement of values in a .ti3 (or other
CGATS file) by using the same file for both "target" and "measured"
values.
The -x flag adds Lab axes to the VRML output.
The -f flag enables Fluorescent Whitening Agent (FWA)
compensation. This only works if spectral data is available and, the
instrument is not UV filtered. FWA compensation adjusts the
spectral samples so that they appear to have been measured using an
illuminant that has a different level of Ultra Violet to the one the
instrument actually used in the measurement. The optional
illumination parameter allows specifying a standard or custom
illumination spectrum to be used as the similated instrument
illuminant, overriding the default D50 or CIE computation
illuminant used for FWA (see -i below). See colprof -f for a fuller explanation. The
same value should be used as was used during the creation of the
profile.
The -i flag allows specifying a standard or custom
illumination spectrum, applied to the spectral test point values to
compute CIE tristimulus values. A, D50, D50M2,
D65, F5, F8, F10 are a selection of
standard illuminant spectrums, with D50 being the default.
If a filename is specified instead, it will be assumed to be an
Argyll specific .sp spectrum
file. If FWA compensation is used during measurement, this
illuminant will be used by default as the simulated instrument
illuminant. The same value should be used as was used during the
creation of the profile.
The -o flag allows specifying a tristimulus observer, and is
used to compute PCS (Profile Connection Space) tristimulus values.
The following choices are available:
1931_2 selects the standard CIE 1931 2 degree
observer. The default.
1964_10 selects the standard CIE 1964 10 degree
observer.
1955_2 selects the Stiles and Birch 1955 2 degree
observer
1978_2 selects the Judd and Voss 1978 2 degree
observer
shaw selects the Shaw and Fairchild 1997 2 degree
observer
The same parameter value should be used as was used during the
creation of the profile.
The -L profile.icm parameter causes colverify to ignore
any patches from the first file that are out of gamut according to
the profile. This can be useful in evaluating accuracy without
tainting it by impossible to reach colors.
The -X file.ccmx option applies the given 3x3
calibration matrix to the values from the second file before doing
any verification. This can be useful in evaluating the effects of a
calibration matrix on raw colorimeter values, against reference
values measured using a spectrometer.
If both CIE and spectral values are present in the input files, the
CIE values will be used by default. Using the -i, -o or -f
flag will force spectral values to be used. The the -i, -o or -f
flags will apply to both the target and measured input files.