gamescope/src/color_helpers.h

#pragma once

#include <cstdint>
#include <cmath>

// Colormetry helper functions for DRM, kindly taken from Weston:
// https://gitlab.freedesktop.org/wayland/weston/-/blob/main/libweston/backend-drm/kms-color.c
// Licensed under MIT.

static inline uint16_t
color_xy_to_u16(float v)
{
	assert(v >= 0.0f);
	assert(v <= 1.0f);
    // CTA-861-G
    // 6.9.1 Static Metadata Type 1
    // chromaticity coordinate encoding
	return (uint16_t)round(v * 50000.0);
}

static inline uint16_t
nits_to_u16(float nits)
{
	assert(nits >= 1.0f);
	assert(nits <= 65535.0f);
	// CTA-861-G
	// 6.9.1 Static Metadata Type 1
	// max display mastering luminance, max content light level,
	// max frame-average light level
	return (uint16_t)round(nits);
}

static inline uint16_t
nits_to_u16_dark(float nits)
{
	assert(nits >= 0.0001f);
	assert(nits <= 6.5535f);
	// CTA-861-G
	// 6.9.1 Static Metadata Type 1
	// min display mastering luminance
	return (uint16_t)round(nits * 10000.0);
}