This repository collects information about next generation (WIP?) color management in Windows, called “Modern Color” or “Advanced Color”.

This is a long-awaited feature so I dig it out before its offical announcement. No NDA violated here.

Read official announcement and documentation from Microsoft:

or the original reverse-engineered pipeline here.

Known Issues

As of Windows 11 24H2, when an MHC calibration is in effect:

Buggy mouse cursor and MPO composition observed on NVIDIA and AMD GPU
- They did get some sort of color transform, but not the desired one
Poor LUT quality on 8-bit output observed on Intel GPU
Conflicts with novideo_srgb

MHC2Gen Tool

As per documentation, an ICC profile with private extension (MHC ICC profile) is required to use modern capabilities documented above.

MHC2Gen is an experimental tool to generate MHC ICC profiles from existing ICC profile created with some random calibration solution.

Currently, only profiles created with DisplayCAL are tested.

💡 The Windows calibration loader must be enabled to load MHC2 transform.

The last release of DisplayCAL calibration loader unconditionally disables a scheduled task of Windows calibration loader. You may need to re-enable \Microsoft\Windows\WindowsColorSystem\Calibration Loader for the profile to be loaded automatically after logout or reboot.

⏬ Download latest release

Example 1: sRGB proofing / clamp / emulation in SDR mode

Matrix: [sRGB to XYZ] -> XYZ to sRGB -> sRGB (or some other custom gamut) to Device RGB -> sRGB to XYZ -> [XYZ to sRGB]

LUT: vcgt(sRGB transfer to device transfer)

MHC2Gen sdr-csc [--source-gamut=<sRGB|AdobeRGB|P3D65|BT2020> | --source-gamut-icc=<icc file>] "C:\...\DisplayCAL\storage\...\MODEL #1 2022-01-01 00-00 0.3127x 0.329y sRGB F-S XYZLUT+MTX.icm" "MODEL CSC sRGB.icm"

Example 2: Create profile for SDR Auto Color Management

Matrix: identity

LUT: vcgt, or vcgt(sRGB transfer to device transfer) if --calibrate-transfer is specified

MHC2Gen sdr-acm [--calibrate-transfer] "C:\...\DisplayCAL\storage\...\MODEL #1 2022-01-01 00-00 0.3127x 0.329y sRGB F-S XYZLUT+MTX.icm" "MODEL SDR ACM.icm"

Example 3: Emulate HDR10 on SDR display

Matrix: [BT2020 RGB to XYZ] -> XYZ to BT2020 RGB -> BT2020 RGB to Device RGB -> BT2020 RGB to XYZ -> [XYZ to BT2020 RGB]

LUT: vcgt(device transfer evaluated with absolute luminance)

MHC2Gen hdr-decode [--min-nits=<override minimun luminance>] [--man-nits=<override maximum luminance>] "C:\...\DisplayCAL\storage\...\MODEL #1 2022-01-01 00-00 0.3127x 0.329y sRGB F-S XYZLUT+MTX.icm" "MODEL PQ10 decode.icm"

The wire signal is converted to SDR but still tagged HDR. This is tricky to use, you need to put Windows in HDR mode but display in SDR mode, possibly with EDID override and/or OSD settings.

Create the device profile with desired maximum luminance and dynamic (local or global) dimming disabled.

Recommendations for creating device ICC profiles

From ledoge/novideo_srgb, another LUT-matrix-LUT solution:

To achieve optimal results, consider creating a custom testchart in DisplayCAL with a high number of neutral (grayscale) patches, such as 256. With that, a grayscale calibration (setting "Tone curve" to anything other than "As measured") should be unnecessary unless your display lacks RGB gain controls, but can lead to better accuracy, especially on poorly behaved displays. The number of colored patches should not matter much. Additionally, configuring DisplayCAL to generate a "Curves + matrix" profile with "Black point compensation" disabled should also result in a lower average error than using an XYZ LUT profile. This advice is based on what worked well for a handful of users, so if you have anything else to add, please let me know.

Notes for SDR Auto Color Management

As of Windows 11 24H2 (26100.1882), only lumi, MHC2 and primaries values in a “valid” MHC ICC profile are used (tone curves and vcgt are ignored). Extra calibration to sRGB (or gamma 2.2[^1]) tone response via MHC2 regamma LUT is needed for optimal results. However, with an “invalid” profile, vcgt will be applied.

Given tone curves in ICC ignored, SDR ACM assumes the display is calibrated to sRGB tone curve, which can be achieved with MHC2 LUT.

It is expected future releases will use more characteristics like tone curves and probably PCS LUT in ICC profile, and preferably without the requirement of MHC2 tag.

Before Windows 11 24H2, SDR Auto Color Management requires a non-HDR-capable display at the moment. You are out of luck of using color managed desktop if your display claims a random HDR mapping (HDRn’t) support.

How to unfuck your ScamHDR 400 or other HDRn’t displays

i.e. How to force disable fake HDR Microsoft has a good tradition that trusting hardware vendors’ marketing scam over professional users. [This also applies to HDR displays.](https://support.microsoft.com/en-us/windows/hdr-settings-in-windows-2d767185-38ec-7fdc-6f97-bbc6c5ef24e6#:~:text=Colors%20do%20not%20display%20correctly%20on%20an%20external%20HDR%2Dcapable%20display.) If your display claims to be HDR-capable, you can disable it in one of the following ways: #### Hiding HDR support * OSD setting * Some display only turns off HDR10 wire signal decoding without hiding HDR capability, i.e. assuming HDR10 wire signal is SDR signal. In this case, [emulating HDR10 on SDR](#example-3-emulate-hdr10-on-sdr-display) can be used to calibrate HDR output. * Override EDID * in Windows registry (cost: 0, effect varies on GPU driver: may have glitches, or can’t override HDR metadata, or still HDR-capable but doesn't turn on HDR mapping, or doesn’t work at all) * with workstation-grade GPUs (at 2x cost with similar performance) * by intercepting EDID in physical link (cost: unlimited) * Use an external box that can override EDID (e.g. a ~$200 3DLUT loader, maybe not HDCP-capable) #### Replacing Replace it with [some][XDR] [professional][Creator Extreme] [display][HX310] (cost: $3.5k+) [ScamHDR 400]: https://displayhdr.org/performance-criteria-cts1-1/ [XDR]: https://www.apple.com/pro-display-xdr/ [Creator Extreme]: https://www.lenovo.com/us/en/p/accessories-and-software/monitors/office/62a6rar3us [HX310]: https://pro.sony/ue_US/products/broadcastpromonitors/bvm-hx310 [auto color management]: https://user-images.githubusercontent.com/2252500/194107647-788c3cab-6730-4728-b337-266ab9867481.png

Notes for ICC shim (Use legacy display ICC color management)

As of Windows 11 24H2 (26100.1882), the synthetic ICC profile uses gamma 2.2 TRC while actual processing uses sRGB TRC.

Applications with ICC shim will still have MHC2 transform applied.

[^1]: Windows SDK headers suppose a gamma 2.2 transfer (OUTPUT_WIRE_COLOR_SPACE_G22_P709) but experiments show that assuming an sRGB transfer function gives better average delta-E on verification (this may vary on GPU vendor).

dantmnf / MHC2

readme