render/color: introduce wlr_color_transform

include/wlr/render/color.h

@@ -0,0 +1,44 @@
+/*
+ * 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.
+ *
+ * The formula is approximated via a 3D look-up table. A 3D LUT is a
+ * three-dimensional array where each element is an RGB triplet. The flat lut_3d
+ * array has a length of dim_len³.
+ *
+ * Color channel values in the range [0.0, 1.0] are mapped linearly to
+ * 3D LUT indices such that 0.0 maps exactly to the first element and 1.0 maps
+ * exactly to the last element in each dimension.
+ *
+ * The offset of the RGB triplet given red, green and blue indices r_index,
+ * g_index and b_index is:
+ *
+ *     offset = 3 * (r_index + dim_len * g_index + dim_len * dim_len * b_index)
+ */
+struct wlr_color_transform {
+	float *lut_3d;
+	size_t dim_len;
+};
+
+/**
+ * Initialize a color transformation to convert sRGB to an ICC profile.
+ */
+bool wlr_color_transform_init_srgb_to_icc(struct wlr_color_transform *tr,
+	const void *data, size_t size);
+
+void wlr_color_transform_finish(struct wlr_color_transform *tr);
+
+#endif