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Define SCRGB_NITS for use in HDR color calculations

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This commit is contained in:
Sam Lantinga
2026-07-23 08:09:02 -07:00
parent b9d64c45a9
commit 148241117b
7 changed files with 20 additions and 14 deletions
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7
test/testcolorspace.c
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@@ -15,6 +15,9 @@
#include <SDL3/SDL_test.h>
#include <SDL3/SDL_main.h>
// The value, in nits, of scRGB 1.0
#define SCRGB_NITS 80.0f
#define WINDOW_WIDTH 640
#define WINDOW_HEIGHT 480
@@ -85,7 +88,7 @@ static void UpdateHDRState(void)
}
SDR_white_level = SDL_GetFloatProperty(props, SDL_PROP_RENDERER_SDR_WHITE_POINT_FLOAT, 1.0f);
HDR_headroom = SDL_GetFloatProperty(props, SDL_PROP_RENDERER_HDR_HEADROOM_FLOAT, 1.0f);
if (((SDR_white_level * 80.0f) * HDR_headroom) == 10000.0f) {
if (((SDR_white_level * SCRGB_NITS) * HDR_headroom) == 10000.0f) {
// The system is advertising the PQ luminance range (10000 nits)
// and tone mapping into the actual display capabilities.
// Let's use a more reasonable range for the gradient test.
@@ -693,7 +696,7 @@ static SDL_Texture *CreateHDR10Texture(int width, float max_nits)
// The white point for HDR10 textures is the SDR white level in nits
if (SDR_white_level > 1.0f) {
// We'll match the current display SDR white level so we don't get any scaling here
SDL_SetFloatProperty(props, SDL_PROP_TEXTURE_CREATE_SDR_WHITE_POINT_FLOAT, SDR_white_level * 80.0f);
SDL_SetFloatProperty(props, SDL_PROP_TEXTURE_CREATE_SDR_WHITE_POINT_FLOAT, SDR_white_level * SCRGB_NITS);
} else {
// ITU-R BT.2408-6 recommends using an SDR white point of 203 nits.
SDL_SetFloatProperty(props, SDL_PROP_TEXTURE_CREATE_SDR_WHITE_POINT_FLOAT, 203.0f);