## Setting an environment variable

To set an environment variable an MSWindows DOS shell, either use set, e.g.;
set ARGYLL_REV_CACHE_MULT=1.5
which will set the value for that session, or set it in
Control Panel->System->Advanced->Environment Variables..
or go to Settings and search for environment.
You can set in either user or system variables.
You can examine individual variables in a command shell using
echo %VARIABLE_NAME%
or
set ARGYLL_REV_CACHE_MULT
or see all of them using
set
To remove an environment variable use
set ARGYLL_REV_CACHE_MULT=
For Mac OS X or Linux, the exact procedure will depend on the shell you are running, but
is usually something like:
export ARGYLL_REV_CACHE_MULT=1.5
or
set ARGYLL_REV_CACHE_MULT=1.5
or
ARGYLL_REV_CACHE_MULT=1.5
and may need separately exporting, something like:
export ARGYLL_REV_CACHE_MULT
If you want the setting to be used for every session, then it should be configured in the shell start-up script. The exact file will depend on which shell you are using, but will typically be ~/.bash_profile, ~/.zshrc, ~/.profile or similar.
On Mac OS X if you need the environment variable seen by all applications (i.e. DisplayCAL), not just those started from a shell, you will have to change the ~/.MacOSX/environment.plist on earlier systems, or /etc/launchd.conf file on later systems. On OS X 10.11 (El Capitan) and later, you will have to create a shell script that sets the environment variables and then starts DisplayCAL.
You can examine individual variables using
echo $VARIABLE_NAME
or see all of them using
set ARGYLL_REV_CACHE_MULT
You can remove an environment variable using
unset
Where an environment variable is used as a flag, the setting it to any value (i.e. "true") will have the effect of setting the flag.
Remove the variable to unset the flag.

## Environment variables

The following environment variables affect behaviour:
ARGYLL_NOT_INTERACTIVE
Normally Argylls tools expect that they are directly interacting with a user, and use a couple of techniques for communicating with them through the console and command line. One is to output progress information by re-writing the same display line by using a Carriage Return rather than a Line Feed at the end of each line. Another is to allow a single key stroke to trigger an action or interrupt operations. This can be a bit difficult to work with when wrapping Argyll tools in a script.
If the ARGYLL_NOT_INTERACTIVE environment variable is set (i.e. set to the value "1"), then:
A Line Feed will be added to the end of each progress line, rather than a Carriage Return.
[ Note that a Line Feed is not added to prompt lines. Prompt lines do not end with a Line Feed, but are flushed to stdout. ]
Any time it would wait for a single console keystroke input, it will instead wait for and read the next character and a return from stdin.
The first character read will be used, and any following return characters ignored.
Note that while a measurement is being made, a character input (i.e. stdin character followed by a return) can abort the reading, just as with normal interactive mode.
On MSWin systems, the character and return or line feed characters must be written to stdin in a single operation.
ARGYLL_3D_DISP_FORMAT

> This overrides the default 3D visualisation file format for tools such as iccgamut or viewgam. Set to VRML or X3D or X3DOM, which will result in .wrl, .x3d and .x3d.html files respectively. See 3d Viewing Format.

ARGYLL_COLMTER_CAL_SPEC_SET
ARGYLL_COLMTER_COR_MATRIX
Both of these can be used to set a default CCMX or CCSS colorimeter calibration file, equivalent to supplying a -X argument to spotread, dispcal, dispread and any other utility that allows using a colorimteter. The ARGYLL_COLMTER_CAL_SPEC_SET will take priority if both are set.
ARGYLL_MIN_DISPLAY_UPDATE_DELAY_MS
Normally a delay of 200 msec is allowed between changing a patch color in software, and that change appearing in the displayed color itself. For some instuments (ie. i1d3, i1pro, ColorMunki, Klein K10-A) ArgyllCMS will automatically measure and set an appropriate update delay during instrument calibration. In rare situations this delay may not be sufficient (ie. some TV's with extensive image processing features turned on), and a larger delay can be set using the ARGYLL_MIN_DISPLAY_UPDATE_DELAY_MS environment variable, ie. ARGYLL_MIN_DISPLAY_UPDATE_DELAY_MS=400 would set a 400 msec minimum delay.
ARGYLL_DISPLAY_SETTLE_TIME_MULT

> Normally the display technology type determines how long is allowed between when a patch color change appears on the display, and when that change has settled down, and as actually complete within measurement tolerance. A CRT or Plasma display for instance, can have quite a long settling delay due to the decay characteristics of the phosphor used, while an LCD can also have a noticeable settling delay due to the liquid crystal response time and any response time enhancement circuitry. [ Instruments without a display technology type selection such as spectrometers assume a worst case.].
> The ARGYLL_DISPLAY_SETTLE_TIME_MULT environment variable allows the rise and fall times of the model to be scaled to extend or reduce the settling time. For instance, ARGYLL_DISPLAY_SETTLE_TIME_MULT=2.0 would double the settling time, while ARGYLL_DISPLAY_SETTLE_TIME_MULT=0.5 would halve it.

ARGYLL_CREATE_WRONG_VON_KRIES_OUTPUT_CLASS_REL_WP

> By default ArgyllCMS uses the Bradford sharpened cone Chromatic adaption matrix in adapting the measured, absolute colorimetric test data to the PCS (Profile Connection Space) relative colorimetric D50 white point for all profile types. This makes the profile handling consistent with the widely deployed (HP & Microsoft) sRGB and AdobeRGB profiles, as well as being recommended practice in modelling chromatic adaption. The ICC profile format though, specifies the use of a non-cone space XYZ adaptation (so called "Wrong Von Kries" chromatic adaptation) [ ICC Specification ICC.1:2001-04 (ICCV2.4) Annex A, pp 66, equations A.1, A.2 & A.3 ], so ArgyllCMS profiles have a very slight incompatibility with ICC profiles created strictly according to the ICC specifications, depending on how close to white Output (i.e. print) profiles media white is to the perfect diffuser. (Note that CMM's that strictly follow the ICC specifications have much more gross incompatibilities due to this, when dealing with the HP & Microsoft sRGB and AdobeRGB profiles.) By setting this environment variable, Output (i.e. print) profiles will be created that better conform to the ICC specification, and therefore have better inter-interoperability with some other CMMs, at the cost of poorer color behavior.
> See also the ArgyllCMS 'arts' tag.

ARGYLL_CREATE_DISPLAY_PROFILE_WITH_CHAD

> The ICC V2 format originally provided no clear mechanism for Display profiles to use a modern chromatic adaptation transform in dealing with the D65 white point of typical displays. Profile makers ended up taking two different approaches :- one was to use a Bradford chromatic transform for the media (display) white to PCS D50 (this approach being used by the widely deployed HP & Microsoft sRGB and AdobeRGB profiles, as well as ArgyllCMS profiles by default), and the other was to apply the Bradford transform to the measurement data and then disable Absolute Intent for display profiles by setting the mediaWhitePoint tag to D50. The latter approach was supplemented later on with the introduction of the ChromaticAdapation ('chad') tag, but this did not restore the Absolute Colorimetric capability to Display profiles. The latter approach has also been adopted more formally in the ICC V4 specifications. To restore the Absolute Intent for such profiles, ArgyllCMS will make use of the 'chad' tag in such profiles when Absolute Colorimetric intent is requested, but by default does not create such profiles.
> Setting this environment variable overrides the ArgyllCMS ICC V2 and default causes it to create Display profiles in the fashion dictated by the ICC V4 spec. :- setting the mediaWhitePoint tag to D50 and storing the display media white to D50 matrix in the 'chad' tag. (This approach has slightly poorer accuracy for Absolute Intent than ArgyllCMS's default.)

ARGYLL_CREATE_DISPLAY_PROFILE_WITHOUT_CHAD

> Setting this environment variable overrides the ArgyllCMS ICC V4 default and causes it to create Display profiles in the fashion used by default when creating an ICC V2 display profile. (See above).

ARGYLL_CREATE_OUTPUT_PROFILE_WITH_CHAD

> For Output type devices (i.e. Printers), the assumption is that test patches are measured under D50 illuminant. It can be very useful for proofing to calculate color corrections for other, real world illuminants, and ArgyllCMS makes provision for this with the coloprof -i parameter, or the spec2cie -i parameter. To be broadly useful, this change in illuminant needs to be available to CMM's, which the ArgyllCMS's implementation makes possible by incorporating the illuminant change into the absolute XYZ values and hence the white point tag, so that Absolute Colorimetric rendering intent returns XYZ values under that illuminant using any CMM.
> The ICC specification have provision for hiding this difference in illuminant by chromatically transforming the absolute values to be functionally equivalent to having been measured using a D50 illuminant, and recording this transform in the ChromaticAdapation ('chad') tag. This appears to motivated by the assumption that the difference in illuminant is a quirk or limitation of the instrument that is to be worked around, as well as the limitation of the ICC Absolute to Relative chromatic transformation being based on the inferior non-cone space XYZ adaptation (so called "Wrong Von Kries" chromatic adaptation), while the ChromaticAdapation tag allows for the use of a superior cone-space based transformation. (see ARGYLL_CREATE_WRONG_VON_KRIES_OUTPUT_CLASS_REL_WP above for more details.)
> To allow for strict conformance to the ICC specification when using non-standard illuminants, setting the ARGYLL_CREATE_OUTPUT_PROFILE_WITH_CHAD environment variable causes a non-D50 illuminant white point change to be hidden in the ChromaticAdapation Tag, and to still allow this to be useful in a proofing situation, ArgyllCMS will incorporate the effect of the ChromaticAdapation Tag when Absolute Colorimetric Intent is chosen. Note that other CMM's may not do so. For full conformance with ICC specifications, the ARGYLL_CREATE_WRONG_VON_KRIES_OUTPUT_CLASS_REL_WP variable would also be set, but neither of these options is recommended, since ArgyllCMS's default behavior will give superior results.

ARGYLL_CREATE_V2COLORANT_TABLE

> ArgyllCMS only supports ICC V2 profiles, but older versions did add the ColorantTable tag to profiles it created. For compatible behavior to the older releases, set the ARGYLL_CREATE_V2COLORANT_TABLE variable. Note that the ColorantTable tag created will be non-standard, in having ICC V2 PCS encoding.

ARGYLL_CCAST_DEFAULT_RECEIVER

> By default the ChromeCast test patch source uses a special receiver application that gets the test patch data directly. By setting this environment variable to true, the default Google ChromeCast receiver will be used, making use of a local web server to provide the images. This is slower than the special reciever, but can be used as a fallback.

ARGYLL_IGNORE_XRANDR1_2

> On an X11 system, if this is set (ie. set it to "yes"), then the presence of the XRandR 1.2 extension will be ignored, and other extensions such as Xinerama and XF86VidMode extension will be used. This may be a way to work around buggy XRandR 1.2 implementations.

ARGYLL_IGNORE_XINERAMA

> On an X11 system, if this is set (ie. set it to "yes"), then the presence of the XInerama extension will be ignored, and default X11 Screen numbering will be used to access multiple displays.

ARGYLL_USE_COLORD

> By default ArgyllCMS >= V 1.9.4 will use its native ucmm to store display ICC profiles on Linux based systems, but if the ARGYLL_USE_COLORD environment variable is set, it will attempt to use the Gnome colord storage instead.

ARGYLL_DISABLE_I1PRO2_DRIVER
ArgyllCMS supports most of the the Eye-One Pro Rev E (aka Eye-One Pro 2) instrument features, but a Rev E can be operated in legacy mode if the environment variable ARGYLL_DISABLE_I1PRO2_DRIVER is set (ie. set it to "yes").
ARGYLL_EXCLUDE_SERIAL_SCAN

> Normally ArgyllCMS will try and identify any device on a fast serial port (i.e. USB or BlueTooth based port). This may disturb devices it doesn't know about, so the ARGYLL_EXCLUDE_SERIAL_SCAN variable can be set to a semi-colon or comma separated list of serial ports that should not be fast scanned. Example:
> "COM2;/dev/tty5" etc.

ARGYLL_XRGA

> If the ARGYLL_XRGA environment variable is set to:
> XRGA, then all Getag-MacBeth/X-Rite reflective measurements will be converted to XRGA.
> XRDI, then all Getag-MacBeth/X-Rite reflective measurements will be converted to XRDI.
> GMDI, then all Getag-MacBeth/X-Rite reflective measurements will be converted to GMDI.
> If not set (or set to some other string), then the native calibration will be used. Note that the values must be upper case.

ARGYLL_UNTWIST_GAMUT_SURFACE

> Whenever a color device profile value is inverted (i.e. in creating ICC B2A tables, or creating a device link using gamut mapping mode), colors that are out of gamut after gamut mapping, will be clipped to the gamut surface. If the device behavior is poor (i.e. non-monotonic), the gamut surface representation used for clipping may have "shadow" areas that result in non-smooth jumps in clipped output. Setting the ARGYLL_UNTWIST_GAMUT_SURFACE environment variable to a non empty value will invoke an additional step in the gamut surface creation routine, that attempts to minimize such shadowed surface areas. This can improve the smoothness of clipped colors for poorly behaved devices, but may make the output for some devices worse.

XDG_CACHE_HOME
Argyll tries to follow the XDG Base Directory Specification, and uses the XDG_CACHE_HOME environment variable to place per instrument calibration information, and .ccmx and .ccss files.
XDG_CONFIG_DIRS
XDG_DATA_DIRS
On Unix type operating systems, configuration and profiles for displays are placed relative to these environment variables.
I1D3_ESCAPE

> Some of the X-Rite i1d3 type colorimeters have unlock codes that are not currently known. If the codes become known, an instrument might be made to work with ArgyllCMS by setting the I1D3_ESCAPE value to the appropriate two 16 character hexadecimal value. For instance, if the retail i1d3 unlock wasn't already built into the ArgyllCMS driver code, it could be enabled by the setting:

> > I1D3_ESCAPE=e9622e9f8d63e133

> Another way of setting extra unlock codes is to create an i1d3_escape file, with one 16 character hexadecimal code per line.
> The file should be in the system DATA location:
> Unix: $HOME/.local/share/ArgyllCMS/i1d3_escape
> OS X: $HOME/Library/Application Support/ArgyllCMS/i1d3_escape
> MSWin: $HOME/.local/share/ArgyllCMS/i1d3_escape

I1D3_DISABLE_AIO

> The X-Rite i1d3 Rev. B type colorimeters have a new measurement command called AIO that has some advantages over the commands supported by the Rev. A hardware, and the ArgyllCMS driver will use this command when it is available. The older older commands can be used on a Rev. B by setting I1D3_DISABLE_AIO.

SPYD2024_LOWLEV_MEASURE

> The Datacolor Spyder and SpyderPro 2024 colorimeters by default use a new high level measurement command that performs a measurement and then computes the XYZ values in the instrument. By setting the SPYD2024_LOWLEV_MEASURE environment variable (i.e. to "true"), the Spyder X2 lower level measurements commands will be used instead, and the conversion to XYZ will be done by the ArgyllCMS driver. This must be set before starting an application.

See Performance Tuning for other variables.