1903641 - Incorrect gamma for background color alpha when Windows ACM is enabled

Status: UNCONFIRMED

(Core :: Graphics: Color Management, defect, P1)

Description

[Andrew Sun]

Attachment: Screenshot 2024-06-19 152141.png

When Windows 11 Auto Color Management is enabled ("Automatically manage color for apps"), background colors with an alpha component (such as those specified with rgba) are displayed with an apparently incorrect gamma for the alpha component. It is especially noticeable in places like the GitHub diff view.

This occurs regardless of whether "Use legacy display ICC color management" is selected in the EXE compatibility options. It also occurs in the latest Firefox Nightly build.

This issue disappears in normal screenshots, however it does appear in OBS desktop capture (not window capture).

Comment 1

[Andrew Sun]

Attachment: S2721DGF SDR ACM.icm

Here is the ICC profile (created with MHC2Gen) that is assigned to my display

Comment 2

[Andrew Sun]

Attachment: Screenshot 2024-06-20 104702.png

I think it is worth mentioning that this has the effect of greatly hurting the readability of some pages, such as the GitHub diff view in the screenshot.

Comment 3

[Jeff Muizelaar [:jrmuizel]]

Ashley, will try to reproduce this.

Comment 4

[Andrew Sun]

FYI - if Windows doesn't show you the option to enable ACM, you may need to set the registry key "AutoColorManagementSupported"=dword:00000001 in HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\GraphicsDrivers\MonitorDataStore\<MONITOR> and possibly some others: https://github.com/mydarknight/MHC2/blob/e0571fc1b82c3c771c1ad15969a0cee6e02a9565/README.md#advanced-color-for-sdr

Comment 5

[Bob Hood [:bhood]]

Setting to P1 for investigation.

Comment 6

[Kelsey Gilbert [:jgilbert]]

It's plausible that rather than gamma being applied to alpha, we're working in alpha-premultiplied colors, which might intermingle things and cause it to look like it's being applied to alpha.

Comment 7

[Ashley Hale [:ahale]]

I'm going to try to spend some time on this bug this week. I agree with Kelsey's speculation that this is an alpha-premultiplied color, and I suspect it is on a primitive that WebRender promoted to opaque because there is nothing behind it as an optimization, so the raw color may have already been changed to be this way, possibly even in Gecko when building the display list. Ideally this needs a wrench reftest and a layout reftest (or WPT reftest, since I'd like to migrate towards using those more).

Comment 8

[wiagn233]

Hello, seems when ACM is enabled, firefox will try to limit some images(that is outside of sRGB range) to sRGB, causing it fail to display properly and making firefox basically unusable.
You can check the following websites for more information.
https://cameratico.com/tools/web-browser-color-management-test/
https://webkit.org/blog-files/color-gamut/

Also, with a chromium-based browser + "Force color profile" set to scRGB linear at chrome://flags/ (this would make those browsers display correctly when ACM is enabled), you can do a compare with it.(Be aware that screenshot won't work here)