Add HDR headroom to ScreenDetailed#150
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ccameron-chromium wants to merge 3 commits intow3c:mainfrom
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cnanda-adobe
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Jul 7, 2025
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| A [=/screen=] has an <dfn>HDR headroom</dfn>, which is the current [=/HDR headroom=] of the screen. | ||
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| Note: The [=screen/HDR headroom=], being the base 2 logarithm of the peak luminance of the screen to the [=/HDR reference white=] luminance of the screen (which is the luminance of '[=/white=]') has to be zero for [=/standard dynamic range=] displays. For [=/high dynamic range=] capable displays it can be zero or greater than zero and can vary over time in response to changes in the presence or absence of HDR content on the screen, screen brightness, ambient brightness, power management feature, and other factors. |
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Sorry, I am missing some details here.
How peak luminance of the screen is specified? Is it read from the OS/display settings?
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Some operating systems (Windows) expose the peak luminance, and the headroom is derived from the ratio.
Other operating systems (macOS, iOS, Android) just expose the ratio and abstract away the peak.
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Fixes #149
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