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A second take on HDR support with an SDR white point and HDR headroom

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This better reflects how HDR content is actually used, e.g. most content is in the SDR range, with specular highlights and bright details beyond the SDR range, in the HDR headroom.

This more closely matches how HDR is handled on Apple platforms, as EDR.

This also greatly simplifies application code which no longer has to think about color scaling. SDR content is rendered at the appropriate brightness automatically, and HDR content is scaled to the correct range for the display HDR headroom.
This commit is contained in:
Sam Lantinga
2024-02-19 08:45:02 -08:00
parent 3b7533f4a2
commit 4ba6aeee9d
24 changed files with 430 additions and 546 deletions
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15
include/SDL3/SDL_video.h
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@@ -355,14 +355,9 @@ extern DECLSPEC SDL_DisplayID SDLCALL SDL_GetPrimaryDisplay(void);
*
* The following read-only properties are provided by SDL:
*
* - `SDL_PROP_DISPLAY_HDR_ENABLED_BOOLEAN`: true if the display has High
* Dynamic Range enabled
* - `SDL_PROP_DISPLAY_SDR_WHITE_LEVEL_FLOAT`: the luminance, in nits, that
* SDR white is rendered on this display. If this value is not set or is
* zero, the value 200 is a reasonable default when HDR is enabled.
* - `SDL_PROP_DISPLAY_HDR_WHITE_LEVEL_FLOAT`: the maximum luminance, in nits,
* of HDR content on this display. If this value is not set or is zero, the
* value 400 is a reasonable default when HDR is enabled.
* - `SDL_PROP_DISPLAY_HDR_ENABLED_BOOLEAN`: true if the display has HDR headroom above the SDR white point.
* - `SDL_PROP_DISPLAY_SDR_WHITE_POINT_FLOAT`: the value of SDR white in the SDL_COLORSPACE_SRGB_LINEAR colorspace. On Windows this corresponds to the SDR white level in scRGB colorspace, and on Apple platforms this is always 1.0 for EDR content.
* - `SDL_PROP_DISPLAY_HDR_HEADROOM_FLOAT`: the additional high dynamic range that can be displayed, in terms of the SDR white point. When HDR is not enabled, this will be 1.0.
*
* \param displayID the instance ID of the display to query
* \returns a valid property ID on success or 0 on failure; call
@@ -376,8 +371,8 @@ extern DECLSPEC SDL_DisplayID SDLCALL SDL_GetPrimaryDisplay(void);
extern DECLSPEC SDL_PropertiesID SDLCALL SDL_GetDisplayProperties(SDL_DisplayID displayID);
#define SDL_PROP_DISPLAY_HDR_ENABLED_BOOLEAN "SDL.display.HDR_enabled"
#define SDL_PROP_DISPLAY_SDR_WHITE_LEVEL_FLOAT "SDL.display.SDR_white_level"
#define SDL_PROP_DISPLAY_HDR_WHITE_LEVEL_FLOAT "SDL.display.HDR_white_level"
#define SDL_PROP_DISPLAY_SDR_WHITE_POINT_FLOAT "SDL.display.SDR_white_point"
#define SDL_PROP_DISPLAY_HDR_HEADROOM_FLOAT "SDL.display.HDR_headroom"
/**
* Get the name of a display in UTF-8 encoding.