render/color: introduce wlr_color_transform

Co-authored-by: Manuel Stoeckl <code@mstoeckl.com>

include/wlr/config.h.in

@@ -14,4 +14,6 @@
 
 #mesondefine WLR_HAS_SESSION
 
+#mesondefine WLR_HAS_COLOR_MANAGEMENT
+
 #endif

include/wlr/render/color.h

@@ -0,0 +1,55 @@
+/*
+ * This an unstable interface of wlroots. No guarantees are made regarding the
+ * future consistency of this API.
+ */
+#ifndef WLR_USE_UNSTABLE
+#error "Add -DWLR_USE_UNSTABLE to enable unstable wlroots features"
+#endif
+
+#ifndef WLR_RENDER_COLOR_H
+#define WLR_RENDER_COLOR_H
+
+#include <stdbool.h>
+#include <sys/types.h>
+
+/**
+ * A color transformation formula, which maps a linear color space with
+ * sRGB primaries to an output color space.
+ *
+ * For ease of use, this type is heap allocated and reference counted.
+ * Use wlr_color_transform_ref()/wlr_color_transform_unref(). The initial reference
+ * count after creation is 1.
+ *
+ * Color transforms are immutable; their type/parameters should not be changed,
+ * and this API provides no functions to modify them after creation.
+ *
+ * This formula may be implemented using a 3d look-up table, or some other
+ * means.
+ */
+struct wlr_color_transform;
+
+/**
+ * Initialize a color transformation to convert linear
+ * (with sRGB(?) primaries) to an ICC profile. Returns NULL on failure.
+ */
+struct wlr_color_transform *wlr_color_transform_init_linear_to_icc(
+	const void *data, size_t size);
+
+/**
+ * Initialize a color transformation to apply sRGB encoding.
+ * Returns NULL on failure.
+ */
+struct wlr_color_transform *wlr_color_transform_init_srgb(void);
+
+/**
+ * Increase the reference count of the color transform by 1.
+ */
+void wlr_color_transform_ref(struct wlr_color_transform *tr);
+
+/**
+ * Reduce the reference count of the color transform by 1; freeing it and
+ * all associated resources when the reference count hits zero.
+ */
+void wlr_color_transform_unref(struct wlr_color_transform *tr);
+
+#endif