In a single printing pass, create and verify accuracy of one or more ICC profiles from one or more sets of RGB profiling patches.
i1Patches Is a Windows based tool principally used to aggregate and randomize one or more, printer profiling patch sets along with randomly generated patches for independent accuracy verification. It produces tif and CGATs files compatible with XRite's i1Profiler and i1iSis or i1Pro2 spectrophotometers.
It is particularly good at removing externalities that strongly affect comparing different profile patch sets. These have been typically evaluated by printing charts, measuring patch color, making profiles, printing sets of known colors with these profiles, and finally, measuring these prints and comparing mesasured colors to patch RGB value colors.
The following can, and does, make this usual practice difficult and uncertain: I've seen these effects result in a 500 patch profile appearing to be more accurate than an 1,800 patch profile.
- Environmental variations such as changes in temperature and humidity that change the dynamics of dot size as ink drys.
- Printer variations that occur between successive page prints from warmup. Inking differences as new ink flows out of cartridges, through supply tubes, and into the print head.
- Print head technology. Canon and Epson heads differ and have different drift characteristics through a print job.
- Printer algorithms. An example is when the printer decides it's time to jiggle the inks partway through a print job. I've noticed on the Canon Pro1000.
- Paper characteristic changes. Each page may not ink the exact same way due to manufacturing or storage variation. For example the first page in a paper package can exhibit significant shifts on papers with high OBA levels due to more air exposure.
Windows 10 x64, XRite i1isis or i1Pro2 Spectrophotometers together with i1Profiler software than can read printed patches and produce a CGATs file. i1Profiler and an i1isis spectro are ideal because the program creates tif image files that have a registration bar on the top and bottom of the chart. These charts can be read from bottom to top. This allows the charts to be optionally scanned in reverse order to create a reversed CGATs file. I1Pro2 charts that are 21 rows by 29 columns can also be created.
CGATs RGBs and printable tif images for scanning with an i1isis or i1Pro2 are created from existing patch sets and/or randomly generated sets. The CGATs RGB files are read, randomized, and combined. A header where the names and sizes of the files are encoded in the initial RGB values. Also, 4 neutrals and 6 CYM colors are added along the right edge of each image. These are used to check printer consistency as each page is printed. Sometimes a print gradually changes as each page is printed. These check colors are used to gather consistency info.
After the printed charts are measured, the "-R" command is used to extract de-randomized measurement files. These have the same RGB values as the original CGATs RGB patch files but also includes measurement data such as L*a*b*, XYZ, Spectra, etc. Each extracted file is used to make ICC profiles and/or evaluate the profiles for accuracy.
A subdirectory showing an example of each of the options is provided and labeled option_# where # is the letter for each option. Readme links below.
Typical use to create charts, measure, and analyze profiles
Options TRC Details
Create a new CGATs file from 1 or more others with optional range selection.
Option A Details
Evaluate CGATs measurements against one or more ICC profiles.
Option C Details
De-randomize and Extract measurement CGATSs files.
Option R Details
Compare two CGATs identical measurement files.
Option S Details
Aggregate one or more CGATs RGB files and random RGB sets.
Option T Details
Synthesize measurement files from an RGB CGATs file and an ICC profile.
Option X Details
Create drift measurement charts and evaluate drift.
Option Z Details
The full example and all required files are in directory .\option_trc. Three batch files, execute_t.bat, execute_r.bat, and execute_c.bat run all the code except for making the 4 ICC profiles which requires i1Profiler. Here's a quick walkthrough. We start with two RGB CGATs patch sets having 400 and 957 patches.
i1Patches -T 33 -e 500 i400.txt o957.txt
The program combines the patches in i400.txt and o957.txt with generated random patches from the "-e 500" option. The generated patches are designed to test device neutral, low saturation, and full gamut accuracy. Two full US letter size tif images, 33 rows by 29 columns, as well as the associated CGATs RGB fwd/rev files are created. The tif files must be printed without color management. They also have registration bars on both the top and bottom to allow reading forward or reverse.
The CGATs RGB files created are rand500__i400__o957.txt (fwd) and rand500__i400__o957r.txt (rev). The reverse set is optional and used to measure the prints in reverse order. This provides a self check. Also supplied are ".txf" aka, Chart files. These have both RGB values and dimension info to initialize i!profiler to prepare to scan the printer charts. These can be dragged and dropped onto the Test Chart tab.
Whether you use the CGATs RGB files or the ".tfx" chart files make sure the printed charts correspond to that which appears in i1Profiler's windows.
See here for an example how forward/reverse scans detected contamination in an i1isis. If a reverse measurement is made it's averaged and the 5 largest dE errors from the forward and reverse files are listed. The measurement files should be saved as CGATS with the same name ending in "_Mn.txt" where n is the uV mode. The reverse measurement file, if made, should have exactly the same name except with an "r" appended to the base name prior to the _Mn.txt. For this example the regular measurement file is: P_rand500__i400__o957_M2.txt. The reverse measurement file, if used, should be named P_rand500__i400__o957r_M2.txt.
The next step is to extract the embedded CGATs files with the command:
i1Patches -R P_rand500__i400__o957_M2.txt
This extracts 3 CGATs measurement files: rand500_M2.txt, i400_M2.txt and o957_M2.txt. Profiles are then made from i400_M2.txt and o957_M2.txt with i1Profiler (in advanced mode) by dragging and dropping them onto the measurement tab.
rand500_M2.txt is the measurement file profiles will be tested against. ICC profiles can then be created using various options such as 16bit or 8bit and high, medium, low lookup table grids. The profiles should be named as desired when created. After creating ICC profiles the next step is to determine the color accuracy of each profile:
i1patches -C rand500_M2.txt i400_small_8bit.icm i400_medium_16bit.icm o957_small_8bit.icm o957_medium_16bit.icm
This analyzes each profile making a histogram of deltaE for device neutral, low saturation, and the full gamut. Here's the summary of the 4 profiles.
Device Neutrals Low Saturation Full Gamut
dE76 dE2k dE76 dE2k dE76 dE2k
1.11 1.11 0.93 0.72 1.18 0.61 i400_small_8bit.icm
0.91 0.86 0.73 0.58 0.99 0.53 i400_medium_16bit.icm
0.85 0.87 0.85 0.67 0.99 0.54 o957_small_8bit.icm
0.47 0.45 0.55 0.43 0.72 0.42 o957_medium_16bit.icm
Here's a histogram of dE2ks for 4, i1Profiler default patch sets as well as my own, crafted, 957 patch set that fits on a single, US Letter page. The 957 crafted patch set produces better profiles than either the default isis 957 patch set or the 1105 Xrite patch set and fits one one page.
The following command created 12 pages of 957 patches each. It combines 5 sets of increasing profile patch counts. It also generates a 1500 patch set for testing accuracy and a smaller, 250 patch set normalized with an existing ICC profile. This can be found in the directory: "Pro1000\isis_range" along with files created from the -R and -C command after printing and scanning.
i1patches -T 33 -e 1500 -e 250 i957_m2.icm p581.txt p1105.txt p2371.txt p4357.txt o957.txt
i1Patches -[T|T2] n_rows [-e size] patch_set1.txt, patch_set2.txt, ...
Create RGB i1Profiler "txf" chart, CGATs, and tif image files. "n_rows" specifies the number of
rows on each page. It must be between 21 and 33 for i1isis, the "-T" option
and exactly 21 for the i1Pro2, the "-T2" option.
There are always 29 columns. Recommend 33 rows for full i1isis profile page size.
The optional "-e size" can be used to create a set of "size" RGB patches to compare
profile performance against. 500 or more will provide reasonable statistical
comparisons of accuracy between profiles. zero or more "-e" options are allowed.
if no size argument is provided, a default of 250 is used.
i1Patches -[T|T2] n_rows [-e size dup_count] patch_set1.txt, patch_set2.txt, ...
Same as above but all the "-e" patches generated are duplicated. This provides a means
of determining how much variation occurs when the same RGB patches printed
in different locations.
i1Patches -[T|T2] n_rows [-e size dup_count random_seed] patch_set1.txt, patch_set2.txt, ...
Same as above but seed can be specified with specific values used to create
the random patch set. This can be useful to check the variation that occurs
by creating multiple patch sets with or without the same RGB values.
For all:
if (size >= 250) add 52 neutral axis RGBs, split remaining among low saturation and full gamut.
if (size > 100) add 18 deutral axis RGBs, split remaining among low saturation and full gamut.
if (size <= 100) add full gamut randomly spread RGB patches.
i1Patches -[T|T2] -n_rows patch_set.txt
Note: n_rows is negative!. No coded structure or randomization applied.
This generates tif files and forward/reverse CGATs RGB files _x appended to
the base name. Useful for making tif profile targets that can be read both forward and
reverse with an i1isis spectro. RGB CGATs file will be expanded
with white patches to be a multiple of 29*n_rows.
It also prevents randomization so produces charts the same as would appear in i1Profiler.
i1Patches -[t|t2] ....
Same as "-T" above but only create i1Profiler iSiS/i1Pro2 "txf" and RGB CGATs files.
It doesn't create tif images files. Use this when using
i1Profiler to print target images from the txf files. The
CGATs files must be used with care to set the
page values to defaults for profile (i1isis) or landscape (i1isis) US letter size.
i1Profiler uses the default patche sizes: 6mm for i1isis (Profile)
and 8mm (Landscape) for i1Pro2 on US letter size paper.
i1Patches -R measurement_file_M2.txt
Extract measurement files. Note that files can end in _M0.txt, _M1.txt of _M2.txt.
Measurement file should be in i1Profiler's CGATs format that includes,
at a minimum, RGB and Lab values. Recommend selecting all fields including
spectral data. For added data integrity, tif files can be scanned
in reverse from bottom to top and last to first page. If a CGATs measurement file
of the same name except ending in r_M#.txt instead of _M#.txt exists the
two files will be averaged and statistics printed on how closely the
patches match. This is useful for detecting transient issues such as lint on the print.
i1Patches -Ra measurement_file_M2.txt
Same as above but also creates an Argyll batch file to generate profiles. Modify as desired.
i1Patches -r measurement_file_M2.txt
Same as above but doesn't extract files. Just outputs statistics.
i1Patches -Rx measurement_file_M2.txt
Only averages and saves the forward and reversee scans and prints stats. The averaged
file will be saved as *_ave_M2.txt. Can be any set of forward/reverse measurement files.
No structure, as produced with "-T" option, is required.
i1Patches -C test_patches_M2.txt profile1.icm profile2.icm ....
Evaluate profile(s) accuracy by determining the Lab values that generated a
corresponding RGB values and comparing them against the measured Lab values.
A high precision search is performed using BtoA profile tables.
i1Patches -c test_patches_M2.txt profile1.icm profile2.icm ....
Same as above but only AtoB tables in profiles are used.
This is faster but less accurate than the "-C" option since only BtoA tables are used.
i1Patches -A cgats_combined.txt cgats1.txt [start stop] cgats2.txt [start stop] ....
Combines and one or more CGATs files. Files can be RGB
only or measurement files but must all have the same type and layout.
Optionally, start and stop indexes can be specified for each cgats. For instance:
"cgats1.txt 10 55" will retrieve the 10'th through 55'th entries.
Multiple ranges can be given. "cgats1.txt 1 5 7 10" will retrieve
the first 9 values skipping the 6th.
After combining the patches are randmized and the CGATs file is saved.
i1Patches -Ad cgats_combined.txt cgats1.txt cgats2.txt ....
Same as above each CGATs file is firsst de-randomized then the optional
[start stop] selection is applied.
i1Patches -a cgats_combined.txt cgats1.txt cgats2.txt ....
Same as above but patches are not randomized or de-randomized
i1Patches -X noise0 noise1 cgats_aggregate_rgb_file.txt iccProfile.icm
Generates pseudo forward/reverse measurement files using reference profile.
Useful for testing and provides patch quaility info that tracks printed
charts without printing. Provides initial guidance for selecting patch sets
to print and test. noise0 and noise1 are the standard deveation of gaussian noise added
to synthesized Lab values from the RGB file.
noise0 should approximate the printer's patch to patch variation. noise1 should
approximate spectro instrument variation when reading the same patches.
I use noise0=.2 and noise1=.05
i1patches -Z rows file.txt
Create printer drift pattern and neutral ramp for testing color patch stability.
A RGB 4x4x4 plus 2:2:30 dev neutrals repeated to fill selected size
rows*29 total patches. rows must be between 21 and 33 inclusive.
Created are an i1isis compatible file.tif and cgats files, file.txt and filer.txt.
i1patches -Z measurementfile1.txt [measurementfile2.txt]
Evaluate patch color consistency and L* ramp to adjust ink levels.
For two files, evaluate statistical differences between the two measurement files. This is
intended to test variation over time of 1 printed chart or comparing measurements
from 2 charts that were printed at different times, possibly with different ink levels
or after changing ink.
i1patches -S file1.txt file2.txt
Compare two measurement files that have the same RGB values in the same sequence.
Useful to look at time variation in colors, paper/ink longevity
Small scanning errors are normal and this provides a way to scan patches and slightly reduce these errors. Errors can also show up that indicate contamination such as dust in the optical path or transient lint on a chart. This is an example where the forward/reverse scan showed significant errors from lint in the i1isis spectro. These were made evaluating very small patch sets but would have cause significant, and unnoticed errors without making a reverse measurement file.
i1patches -r P_rand1432__Neut50__t189__t216__t512__t559__t729X_M2.txt
6 black patches, ave Lab: 2.00 -0.05 -0.36
6 white patches, ave Lab: 94.76 -1.52 -1.85
33 rows, 4 pages
....
Forward/Reverse stats, 5 worst dEs
Patch# dE76 RGB Lab Forward Lab Reverse page row column
14 4.19 0 116 55 18.79 -34.48 -7.55 19.73 -30.48 -6.73 1 14 1
1924 4.02 9 16 11 6.47 -0.68 0.53 8.77 1.80 2.71 3 10 1
979 3.96 28 152 24 32.93 -44.37 18.06 33.77 -40.52 18.45 2 22 1
26 3.18 16 0 61 10.07 21.42 -16.37 11.88 20.93 -13.80 1 26 1
223 2.85 255 128 0 69.84 37.62 89.56 69.81 37.15 86.75 1 25 7
dE76 distribution (less than)
10% 20% 30% 40% 50% 60% 70% 80% 90% 95% 99%
0.08 0.10 0.13 0.15 0.17 0.20 0.23 0.27 0.35 0.53 1.58
This is fairly rare. I've only seen it a few times. In this case the instrument was opened up and pressurized air use to remove contamination. New forward/reverse scans produced this more typical results:
Forward/Reverse stats, 5 worst dEs
Patch# dE76 RGB Lab Forward Lab Reverse page row column
2219 0.70 0 255 96 38.68 -77.98 -3.66 38.90 -77.33 -3.50 3 8 10
2058 0.65 255 219 0 83.68 6.85 104.18 83.24 6.78 103.70 3 12 5
1140 0.57 255 0 64 49.12 76.90 57.11 48.99 76.66 56.61 2 18 6
2206 0.53 0 73 0 17.82 -25.77 10.25 17.69 -26.28 10.30 3 28 9
2789 0.51 49 32 0 16.73 8.45 15.81 16.87 8.42 15.32 3 17 27
dE76 distribution (less than)
10% 20% 30% 40% 50% 60% 70% 80% 90% 95% 99%
0.06 0.08 0.10 0.12 0.14 0.16 0.18 0.21 0.25 0.29 0.37