Argyll CMS documentation index (V1.3.6)

Date:   19th March 2012
Author: Graeme Gill

Introduction

ArgyllCMS is an ICC compatible color management system, available as Open Source. It supports accurate ICC profile creation for acquisition devices, cameras and film recorders, and calibration and profiling of displays and RGB & CMYK printers. Spectral sample data is supported, allowing a selection of illuminants observer types, and paper fluorescent whitener additive compensation. Profiles can also incorporate source specific gamut mappings for perceptual and saturation intents. Gamut mapping and profile linking uses the CIECAM02 appearance model, a unique gamut mapping algorithm, and a wide selection of rendering intents. Device Link can be created with a wide variety of advanced options. It also includes code for the fastest portable 8 bit raster color conversion engine available anywhere, as well as support for fast, fully accurate 16 bit conversion. Device color gamuts can also be viewed and compared using a VRML viewer. Comprehensive documentation is provided for each major tool, and a general guide to using the tools for typical color management tasks is also available. A mailing list provides support for more advanced usage.

This is Version 1.3.6, a feature enhancement update to V1.3.5 released on 24th October 2011. The first public release of icclib was in November 1998, and of Argyll was in October 2000. Code development commenced in 1995. See Changes Summary for an overview of changes since the last release. Changes between revisions is detailed in the log.txt file that accompanies the source code.

The latest source code is available from here.

Argyll is known to compile and run in at least nine environments:

1) MSWindows 2K system using Microsoft VC++ 6.0 compiler
2) MSWindows 2K system using Microsoft VC++ 8.0 Express compiler + Platform SDK Feb. 2003
3) MSWindows 2K system using Microsoft VC++ 9.0 Express compiler + Platform SDK Feb. 2003
4) MSWindows 2K system using the MingW port of the GCC compiler
5) Linux on Fedora Core 8, 32 bit using gcc
6) Linux on Fedora Core 8, 64 bit using gcc
7) Apple OSX 10.3 PPC using gcc
8) Apple OSX 10.4 Intel using  gcc
9) Apple OSX 10.5 Intel using  gcc

It is also known to run on:

 MSWindows 2000, XP, Vista & Windows 7 32 bit.
 MSWindows Vista 64bit & Windows 7 64bit
 Linux Ubuntu 7.10
 Linux Kubuntu 7.10
 Linux Mandriva 2008.0
 Linux OpenSuSE 10.3
 Linux Whitebox 4.2/2
 Apple OSX 10.6 Intel
 Apple OSX 10.7 Intel

but may well compile and run correctly in many more than this.

This is a command line terminal only environment. Those unfamiliar with command line environments should consult an appropriate tutorial for their environment if they are interested in using this software. See the listing of tutorials below.

The following color measuring instruments are directly supported:

X-Rite:
    DTP20 "Pulse"                              - "swipe" type reflective spectrometer, that can be used untethered.
    DTP22 Digital Swatchbook            - spot type reflective spectrometer.
    DTP41                                         - spot and strip reading reflective spectrometer.
    DTP41T                                       - spot and strip reading reflective/transmissive spectrometer.
    DTP51                                         - strip reading reflective colorimeter.
    DTP92                                         - CRT display colorimeter.
    DTP94 "Optix XR" or "Optix XR2" or "Optix Pro"- display colorimeter.
    ColorMunki Design or Photo           - spot and "swipe" reflective/emissive spectrometer (UV cut only).
    ColorMunki Create                         - display colorimeter. (Treated as a Eye-One Display 2)
    Lenovo W                                     - built in laptop Huey display colorimeter.
    Eye-One Display 3                         - Xrite i1 DisplayPro and ColorMunki Display
                                                          [ The OEM i1Display Pro and
                                                             NEC SpectraSensor Pro are also reported to work.]

Gretag-Macbeth (now X-Rite):
    Spectrolino                                   - spot reflective/emissive spectrometer.
    SpectroScan                                 - spot reflective/emissive, XY table reflective spectrometer  .
    SpectroScanT                               - spot reflective/emissive/transmissive, XY table reflective spectrometer.
    Eye-One Pro "EFI ES-1000"           - spot and "swipe" reflective/emissive spectrometer.
    Eye-One Monitor                           - spot and "swipe" emissive spectrometer.
    Eye-One Display 1 or 2  or LT        - display colorimeter.
    HP DreamColor or APS                  - display colorimeter. (Treated as a Eye-One Display 2)
    CalMAN X2                                  - display colorimeter. (Treated as a Eye-One Display 2)
    Huey                                            - display colorimeter.

Sequel imaging (Now X-Rite):
     MonacoOPTIX                             - display colorimeter (Treated as an Eye-One Display 1)
                                                           [The Sequel Chroma 4 may also work.]

Lacie Blue Eye:                                  - see Eye-One Display

DataColor ColorVision:
     Spyder 2                                      - display colorimeter (Note that the user must supply firmware)
                                                          [The Spyder 1 has also been reported as working, but this has not been confirmed.]
     Spyder 3                                      - display colorimeter.
     Spyder 4                                      - display colorimeter (Note that the user must supply calibration data)

Other:
    Colorimètre HCFR                          - display colorimeter (Not on MSWindows 64 bit)

See Operation of particular instruments for more instrument specific detail.

Please note that instruments are being driven by ArgyllCMS drivers, and that any problems or queries regarding instrument
operation should be directed to the Argyll's author(s) or the Argyll mailing list, and not to any other party.


There is a list of contributed ccmx (Colorimeter Correction Matrix) files for some display/colorimeter combinations.

Other instruments can be supported indirectly, since patch result files created by other packages can be imported into Argyll.

Please note the installation instructions for each platform - they contain important information for getting your instruments working.

If you've decided to buy a color instrument because Argyll supports it, please let the dealer and manufacturer know that "You bought it because Argyll CMS supports it" - thanks.

Please direct any queries or problems regarding operation of color instruments in combination with Argyll, to the Author(s) of Argyll, and not to any other party.

Copyright and Licensing:

Most of the source code and provided executable files are copyrighted works, licensed under the Affero GNU Version 3 license, and therefore they (or works derived from them) can't be copied, sold or made available to users interacting with them remotely through a computer network, without providing the source code. Nothing other than your agreement and compliance with the Affero GNU License grants you permission to use, modify or distribute Argyll source code, executables or its derivative works. You could be sued for copyright infringement if you use or distribute Argyll without a valid license. The Affero GNU license prohibits extending these tools (i.e. by combining them with other programs or scripts that make use of, depend on, or work with the Argyll code) and distributing them, unless the all the elements of the extensions are also made available under a GPL compatible license. It is permissible to provide Argyll tools with other non GPL components if the elements of the package are not related, such that the packaging is mere aggregation. For all the gory details, please read the accompanying license.

Note that unlike many commercial ICC profiling tools, the profiles created using Argyll, are not subject to any claims or restrictions of Argyll's author(s), but are assumed to be the copyright property of the person who gathers the characterization data, and causes the profiles to be created.

The Argyll CMS is Copyright 1995 - 2012 Graeme W. Gill, and is made available under the terms of the Affero GNU General Public License Version 3, as detailed in the License.txt file. Documentation is licensed under the terms of the GNU Free Documentation License, Version 1.3. The author asserts his moral rights over this material in relationship to the attribution and integrity of these works. In particular, if these works are modified in a way that materially changes their functionality, then the modified works should be renamed in a way that clearly distinguishes them from "Argyll" or "ArgyllCMS" so that the effects of such changes do not reflect on the original works integrity or the original authors reputation. A subset of files (those that are related to the color istrument drivers, and are collected together into the instlib.zip archive by the spectro/instlib.ksh script) are licensed under the General Public License Version 2 or later, as detailed in the License2.txt file.

Portions of the ColorHug instrument library (spectro/colorhug.[ch]) are Copyright 2011, Richard Hughes, and is licensed under the General Public License Version 2 or later, as detailed in the License2.txt file.

The tool spectro/spec2cie.c is Copyright 2005 Gerhard Fuernkranz, and is made available under the terms of the GNU General Public License Version 2 or later, and is licensed here under the Version 3 license, as detailed in the License3.txt file.

The UNIX USB library libusb included in this distribution, is copyright Johannes Erdfelt, Thomas Sailer and Brad Hards, and is licensed under the GNU LGPL Version 2 or later. See  libusb/LICENSE and libusb/COPYING for details.

The Win32 USB library libusb-win32, included in this distribution, is copyright Stephan Meyer, Johannes Erdfelt and Thomas Sailer, and is licensed under the GNU LGPL Version 2 or latter (the DLL)  and GNU GPL Version 2 or later (the drivers, services, installer). See  libusbw/License.txt, libusbw/COPYING_LGPL.txt and libusbw/COPYING_GPL.txt for details.

The USB library libusb V1.0 included in this distribution, is copyright by the authors listed in the libusb1/AUTHORS file, and is licensed under the GNU LGPL Version 2 or later. See  libusb1/COPYING for details of this license. The MSWindows kernel driver is Copyright Stephan Meyer, and is licesed under the GNU GPL Version 2 or later - See libusb1/KDRIVER_LICENSE and libusb1/COPYING_GPL. The WinUSB CoInstaller redistributable files from the Microsoft Windows Driver Kit are  licensed by Microsoft according to the terms indicated in the libusb1/license.rtf file, section 2. These operating system files are provided ("aggregated") here under the terms of the Microsoft license purely for convenience, and do not form part of the libusb V1.0 package, and are therefore not subject to the terms of the libusb V1.0 license(s). The .inf files that make use of the CoInstallers are provided under a free use, "MIT" type license.

The icc library in icc/, the CGATS library in cgats/, the jcnf library in jcnf/, the files spectro/xdg_bds.*, spectro/aglob.* and the ucmm library in ucmm/ are Copyright 1995 - 2011 Graeme W. Gill, and available according to the "MIT" license granted in the icc/License.txt and cgats/License.txt files, and the licenses at the top of ucmm/ucmm.c and jcnf/jcnf.c.

The yajl library in jcnf/yajl is Copyright 2007-2009, Lloyd Hilaiel and is licensed according to the Berkeley-style License granted in the jcnf/yajl/COPYING files. The yajl library has been repackaged and modified slightly for convenience.

The TIFF library included in this distribution for convenience, has its own copyright and license detailed in tiff/COPYRIGHT (an "MIT"/"BSD" like license).

What sort of project is this ? (re: contributions)

This is essentially my private project, that I've made available under GNU licensing conditions. Because I license my code under other licenses as well, there is a limit to what I will accept in the way of code contributions back into this project. For me to accept contributions into the distribution, it either has to be a non-core (side) project, or has to be offered to me with copyright conditions that are compatible with my other uses (i.e.. a "BSD" like license, or assigning or licensing the copyright to me), or has to be so trivial (say a one line bug fix), that it can't be the subject of copyright.

Of course there is nothing to stop someone setting up a real free software, community project based on the GNU licensed code made available here, that would be able to take GNU licensed contributions from everyone and would essentially be a "fork" of this code base.

Compiling

How to build the software from the source if you want to.
Note that you don't need to do this if you are using one of the binary installations.

Installing

Important notes on installing the binary software on various platforms.

Graphic User Interfaces

ArgyllCMS does not directly support a graphic user interface, but several people have written GUI based front ends for it. A popular front end that supports display calibration and profiling is dispcalGUI by Florian Höch. Others can be found with a suitable search.

Main Tools and the command line

These are all command line ("DOS" shell) tools, and each tool require appropriate options to be set, followed by filename arguments. Sometimes the filenames will have to include the usual extensions, sometimes they are implicit. To get a brief listing of the possible arguments and usage of any of the tools, run it with just an "-?" argument, i.e. targen -? (or some other unrecognized flag, if the "?" character is treated specially in your shell, i.e. try "--" on OS X zsh).

Note that in general the arguments consist of possible flags or options followed by file name arguments. All arguments need to be separated by whitespace.  (If you need to specify a string with embedded white space, double quote the string). A flag consists of a dash attached to a single letter, the letter identifying the flag, and is usually case sensitive. An option is a flag that has an associated parameter or parameters. The parameter can be separated from the flag by white space, or may come directly after the flag. So if a tool has a usage that looks like this:

  tool -?
  usage: tool [options] infile outfile
   -v                   Verbose mode
   -d n                Choose a depth 0-4
   -r                   Use a random depth
   -f [nn]            Use full range. nn optional range 0 - 100.
   -M                  Manual
   infile                Input file
   outfile             Output file

then there are  5 flags/options, and two filename arguments. Notice that square braces [] denote optional items. The first flag/option is a flag. The second is an option that has a numerical argument in the range 0 to 4. The third is a flag. the fourth is an option with an optional argument. The fourth is a flag.  The flags and options can generally be in any order, but must be before the file name arguments. (For a few special tools you actually specify a sequence of flags and files where the flags apply just to the following file.) So example invocations may look like:

  tool -v testin testout
  tool -d3 -M testin1 testout2
  tool -f infile outfile
  tool -f 45 infile outfile
  tool -d 3 -f67 infile outfile

In order to make use of the tools, it is necessary to keep track of where various files are, and what they are called. There are many possible ways of doing this. One way is to put each source profile and all its associated files (test charts, spectrometer values etc.) in one set of directories for each source profile type. Similarly the device profiles could be stored in a hierarchy of directories ordered by device type, media, resolution, device mode etc. Naturally you will want to set your $PATH so that you can run the tools from whichever directory you are in, as well as specify any necessary directory paths for file arguments so that the tools are able to open them.

Note that there are two ways the Argyll tools deal with filename extensions. In one you supply the extension (ie. you supply the whole file name), so the extension is up to you. In the other (used where one name is used for input and output files, or where there are multiple output files), the program adds the extension. In the documentation this should be indicated by calling it a "base name".

For more information on using a command line environments, consult an appropriate tutorial:

MS Windows :
   <http://www.bleepingcomputer.com/tutorials/tutorial76.html>
   <http://www.pcstats.com/articleview.cfm?articleid=1723&page=1>
   <http://www.voidspace.org.uk/python/articles/command_line.shtml>

    To find more: <http://www.google.com/search?hl=en&q=windows+command+prompt+tutorial>

OS X:
    <http://www.osxfaq.com/Tutorials/LearningCenter/>
    <http://www.atomiclearning.com/macosxterminalx.shtml>
    <http://www.oreillynet.com/pub/a/mac/2001/12/14/terminal_one.html>

    To find more: <http://www.google.com/search?hl=en&q=OS+X+shell+tutorial>

Linux:
    <http://www.linuxcommand.org/index.php>
    <http://www.tuxfiles.org/linuxhelp/shell.html>
    <http://www.ee.surrey.ac.uk/Teaching/Unix/>

    To find more: <http://www.google.com/search?q=linux+command+line+shell+tutorial>


Note that since OS X is based on UNIX, there is much in common between the OS X and Linux command line environments, and many of the UNIX tutorials may be useful:

    <http://www.rain.org/~mkummel/unix.html>

Tutorial: Typical usage scenarios and examples

A guided tour of the major tools, applied to typical CMS jobs, such as calibrating displays, creating device profiles, calibrating printers, linking profiles, and converting color spaces of raster files.
 

Topical Discussions

Discussions about particular topics:

About Fluorescent Whitening Agent compensation

Operation of particular instruments

About ICC profiles and Gamut Mapping

About display monitor settings and targets

About display "Gamma"

What's the difference between Calibration and Characterization ?

Why doesn't my Colorimeter work well on my Wide Gamut display ?

My blacks get crushed on my display - why ? How do I fix it ?

How can I have confidence in the i1pro Driver ?

Evaluating input targets

Flow diagram of Major Tools:


          Thumbnail of Flow Diagram

Main Tools by category:

Calibrating devices

dispcal       Adjust, calibrate and profile a display.
printcal      Create a printer calibration .cal file from a .ti3 data file.

Creating test targets for profiling or print calibration

targen        Generate a profiling test target values .ti1 file.
filmtarg      Create film recorder TIFF files from Argyll .ti1 file.
printtarg     Create a PS, EPS or TIFF file containing test patch values, ready for printing.

Obtaining test results for profiling or print calibration

chartread     Read a test chart using an instrument to create a .ti3 data file.
dispread      Test and read colorimetric values from a display
filmread      Read film colorimetric values using a SpectroScanT (Deprecated ?)
scanin        Convert a TIFF  image of a test chart into .ti3 device values.
illumread     Use an instrument to measure an illuminant spectrum, and estimate its UV content.
fakeread      Fake the reading of a device using an ICC or MPP profile.
synthread     Fake the reading of a device using a synthetic device model.
cb2ti3        Convert Colorblind format CMY/RGB test chart into Argyll .ti3 CGATS format.
kodak2ti3     Convert Kodak Colorflow format CMYK test chart into Argyll .ti3 CGATS format.
txt2ti3       Convert Gretag/Logo/X-Rite or other format RGB or CMYK test chart results into Argyll .ti3 CGATS format.
fakeCMY       Create a fake Argyll .ti3 CMY data file from a CMYK profile, as a basis of creating a CMY to CMYK separation
average       Average / Merge two measurement data files

Creating Device Profiles

colprof       Create an ICC profile from the .ti3 test data.
mppprof       Create a Model Printer Profile (MPP) from the .ti3 test data.
sepgen        IN DEVELOPMENT Create a CMY[K] to device colorant separation.
revfix        Regenerate a device profiles B2A table data by inverting the A2B table.

Creating Device Link Profiles

collink       Link two device ICC profiles to create a device link profile.

Converting colors or applying print calibration

cctiff        Color convert a TIFF file using a sequence of ICC device, device link, abstract profiles and calibration files.
applycal      Apply calibration curves to an ICC profile.
icclu         Lookup individual color values through any ICC profile table.
xicclu        Lookup individual color values forward or inverted though an ICC profile table.
mpplu         Lookup individual color values though an MPP profile. Also create MPP gamut files/views.
greytiff      Convert a TIFF file to monochrome using an ICC device profile

Color Tweaking tools

refine        Creates an abstract profile from two chart readings, useful for refining proofing profiles.

Creating gamut views

iccgamut      Create a gamut file or VRML file of the color gamut of an ICC profile.
tiffgamut     Create a gamut file or VRML file of the color gamut of a TIFF image.
viewgam       Convert one or more gamuts into a VRML 3D visualization file. Compute an intersection.

Diagnostic and test tools

iccdump       Dump the contents of an ICC profile as text.
profcheck     Check an ICC profile against .ti3 test chart data.
invprofcheck  Check ICC forward against inverse lookup.
splitsti3     Split a CGATS file (ie. a .ti3) into two parts randomly to verify profiling.
timage        Create TIFF test images.
mppcheck      Check an MPP profile against .ti3 test chart data.
spotread      Use an instrument to read a single spot color value.
verify        Verify matching of CIE in two CGATS/.ti3 files (also view differences as VRML)
synthcal      Create a synthetic input, display or output calibration (.cal)file.

Other Tools

ccxxmake      Use a Spectrometer to create a Colorimeter Correction Matrix (CCMX)  or a Colorimeter Calibration Spectral Set (CCSS)  for a particular display.
extracticc    Extract an embedded ICC profile from a TIFF file.
extractttag   Extract a text tag (ie. CGATS .ti3 data or CAL) from an ICC profile.
dispwin       Install or uninstall display profile, set display calibration from profile or .cal file, test displace and dispwin access to a display.
i1d3ccss      A special purpose tool that can either install CCSS files, or locat and translate X-Rite .EDR files to CCSS files and install them.
specplot       Plot a spectrum (.sp) and calculate CCT and VCT.
spec2cie      Convert spectral .ti3 readings into CIE XYZ or L*a*b* readings. Apply FWA, plot spectrums.
spyd2en       A special purpose tool that enables the Spyder 2 colorimeter.
spyd4en       A special purpose tool that enables the full range of Spyder 4 colorimeter calibration choices.
 

Main Tools Alphabetic Listing:

applycal      Apply calibration curves to an ICC profile.
average       Average / Merge two measurement data files
cb2ti3        Convert Colorblind format CMY/RGB test chart into Argyll .ti3 CGATS format.
cctiff        Color convert a TIFF file using a sequence of ICC device, device link, abstract profiles and calibration files.
ccxxmake      Use a Spectrometer to create a Colorimeter Correction Matrix (CCMX)  or a Colorimeter Calibration Spectral Set (CCSS)  for a particular display.
chartread     Read a test chart using an instrument to create a .ti3 data file.
collink       Link two device ICC profiles to create a device link profile.
colprof       Create an ICC profile from the .ti3 test data.
dispcal       Adjust, calibrate and profile a display.
dispread      Test and read colorimetric values from a display
dispwin       Install or uninstall display profile, set display calibration from profile or .cal file, test displace and dispwin access to a display.
extracticc    Extract an embedded ICC profile from a TIFF file.
extractttag   Extract a text tag (ie. CGATS .ti3 data or CAL) from an ICC profile.
fakeCMY       Create a fake Argyll .ti3 CMY data file from a CMYK profile, as a basis of creating a CMY to CMYK separation
fakeread      Fake the reading of a device using an ICC or MPP profile.
filmread      Read film colorimetric values using a SpectroScanT (Deprecated ?)
filmtarg      Create film recorder TIFF files from Argyll .ti1 file.
greytiff      Convert a TIFF file to monochrome using an ICC device profile
i1d3ccss      A special purpose tool that can either install CCSS files, or locat and translate X-Rite .EDR files to CCSS files and install them.
iccdump       Dump the contents of an ICC profile as text.
iccgamut      Create a gamut file or VRML file of the color gamut of an ICC profile.
icclu         Lookup individual color values through any ICC profile table.
illumread     Use an instrument to measure an illuminant spectrum, and estimate its UV content.
invprofcheck  Check ICC forward against inverse lookup.
kodak2ti3     Convert Kodak Colorflow format CMYK test chart into Argyll .ti3 CGATS format.
mppcheck      Check an MPP profile against .ti3 test chart data.
mpplu         Lookup individual color values though an MPP profile. Also create MPP gamut files/views.
mppprof       Create a Model Printer Profile (MPP) from the .ti3 test data.
printcal      Create a printer calibration .cal file from a .ti3 data file.
printtarg     Create a PS, EPS or TIFF file containing test patch values, ready for printing.
profcheck     Check an ICC profile against .ti3 test chart data.
refine        Creates an abstract profile from two chart readings, useful for refining proofing profiles.
revfix        Regenerate a device profiles B2A table data by inverting the A2B table.
scanin        Convert a TIFF  image of a test chart into .ti3 device values.
sepgen        IN DEVELOPMENT Create a CMY[K] to device colorant separation.
spec2cie      Convert spectral .ti3 readings into CIE XYZ or L*a*b* readings. Apply FWA, plot spectrums.
specplot       Plot a spectrum (.sp) and calculate CCT and VCT.
splitsti3     Split a CGATS file (ie. a .ti3) into two parts randomly to verify profiling.
spotread      Use an instrument to read a single spot color value.
spyd2en       A special purpose tool that enables the Spyder 2 colorimeter.
spyd4en       A special purpose tool that enables the full range of Spyder 4 colorimeter calibration choices.
synthcal      Create a synthetic input, display or output calibration (.cal)file.
synthread     Fake the reading of a device using a synthetic device model.
targen        Generate a profiling test target values .ti1 file.
tiffgamut     Create a gamut file or VRML file of the color gamut of a TIFF image.
timage        Create TIFF test images.
txt2ti3       Convert Gretag/Logo/X-Rite or other format RGB or CMYK test chart results into Argyll .ti3 CGATS format.
verify        Verify matching of CIE in two CGATS/.ti3 files (also view differences as VRML)
viewgam       Convert one or more gamuts into a VRML 3D visualization file. Compute an intersection.
xicclu        Lookup individual color values forward or inverted though an ICC profile table.

Environment Variables

Performance/memory tuning hints, plus tweaks for scipting.

Performance Tuning

Performance hints.

Overview

Overview of the software and its aims and functionality.

Limitations

Limitations of the current functionality.

Organization

How directories are organized, what they contain.

Source

Any detailed documentation on how the software works, or what algorithms it is based on. (Very incomplete.)

Minor Tools

A very brief description of minor tools and test harnesses.


File formats that Argyll uses

Argyll uses a number of file formats for its operation, some that are external standards, and some that are unique to Argyll.

.ti1            Device test values
.ti2            Device test values & chart layout
.ti3            Device test values & CIE tristimulus/spectral results  Format details.
.cal            Device calibration information. Format details.
.cht           Test chart recognition template. Format details.
.gam         3D gamut surface description
.sp            Illuminant spectral description
.ccmx        Colorimeter Correction Matrix
.ccss         Colorimeter Calibration Spectral Set
CGATS      Standard text based data exchange format
ICC           International Color Consortium profile format
MPP          Model device profile format
TIFF         Tag Image File Format raster files.
VRML       Virtual Reality Modelling Language 3D file format.

ucmm       Unix micro Color Management Module convention and configuration file format and Profile Locations.
 

Errors, Corrections and Omissions:

If you notice any errors, corrections needed or omissions in the current documentation, please contact the author.