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Document the HDR tone mapping algorithm

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This commit is contained in:
Sam Lantinga 2024-02-26 14:16:41 -08:00
parent 1f536a1e77
commit 98b1a59a95
1 changed files with 11 additions and 0 deletions
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11
src/video/SDL_blit_slow.c
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@ -699,6 +699,17 @@ static void TonemapLinear(float *r, float *g, float *b, float scale)
*b *= scale;
}
/* This uses the same tonemapping algorithm developed by Google for Chrome:
* https://colab.research.google.com/drive/1hI10nq6L6ru_UFvz7-f7xQaQp0qarz_K
*
* Essentially, you use the source headroom and the destination headroom
* to calculate scaling factors:
* tonemap_a = (dst_headroom / (src_headroom * src_headroom));
* tonemap_b = (1.0f / dst_headroom);
*
* Then you normalize your source color by the HDR whitepoint,
* and calculate a final scaling factor in BT.2020 colorspace.
*/
static void TonemapChrome(float *r, float *g, float *b, float tonemap_a, float tonemap_b)
{
float v1 = *r;