From 10b8880fc7344dae3c44ae87c536d3a0fbf7aabe Mon Sep 17 00:00:00 2001
From: Simon Ser <contact@emersion.fr>
Date: Wed, 26 Feb 2025 08:58:15 +0100
Subject: [PATCH] render/color: add
 wlr_color_transfer_function_get_default_luminance()

---
 include/render/color.h     |  6 ++++++
 include/wlr/render/color.h |  7 +++++++
 render/color.c             | 20 ++++++++++++++++++++
 3 files changed, 33 insertions(+)

diff --git a/include/render/color.h b/include/render/color.h
index 9da4f9a74..cddf1e219 100644
--- a/include/render/color.h
+++ b/include/render/color.h
@@ -56,4 +56,10 @@ void wlr_color_primaries_from_named(struct wlr_color_primaries *out,
  */
 void wlr_color_primaries_to_xyz(const struct wlr_color_primaries *primaries, float matrix[static 9]);
 
+/**
+ * Get default luminances for a transfer function.
+ */
+void wlr_color_transfer_function_get_default_luminance(enum wlr_color_transfer_function tf,
+	struct wlr_color_luminances *lum);
+
 #endif
diff --git a/include/wlr/render/color.h b/include/wlr/render/color.h
index 32d8e9540..dc6f4097f 100644
--- a/include/wlr/render/color.h
+++ b/include/wlr/render/color.h
@@ -42,6 +42,13 @@ struct wlr_color_primaries {
 	struct wlr_color_cie1931_xy red, green, blue, white;
 };
 
+/**
+ * Luminance range and reference white luminance level, in cd/m².
+ */
+struct wlr_color_luminances {
+	float min, max, reference;
+};
+
 /**
  * A color transformation formula, which maps a linear color space with
  * sRGB primaries to an output color space.
diff --git a/render/color.c b/render/color.c
index ece6b38bd..c708938c7 100644
--- a/render/color.c
+++ b/render/color.c
@@ -128,3 +128,23 @@ void wlr_color_primaries_to_xyz(const struct wlr_color_primaries *primaries, flo
 	};
 	memcpy(matrix, result, sizeof(result));
 }
+
+void wlr_color_transfer_function_get_default_luminance(enum wlr_color_transfer_function tf,
+		struct wlr_color_luminances *lum) {
+	switch (tf) {
+	case WLR_COLOR_TRANSFER_FUNCTION_ST2084_PQ:
+		*lum = (struct wlr_color_luminances){
+			.min = 0.005,
+			.max = 10000,
+			.reference = 203,
+		};
+		break;
+	default:
+		*lum = (struct wlr_color_luminances){
+			.min = 0.2,
+			.max = 80,
+			.reference = 80,
+		};
+		break;
+	}
+}