frontend: create automatic color profiles from .ini

This introduces a new key for outputs in weston.ini, "color-profile".
For starters, implement a pre-defined sRGB profile and an automatic
profile.

Automatic color profiles are created based on the colorimetry-mode and
the eotf-mode of the output. EDID can also be taken into account, but it
is opt-in due to its potential unreliability.

This feature is documented as not fully implemented, because color-lcms
does not yet handle parametric color profiles together with ICC
profiles. Specifically, the stock sRGB profile is still an ICC profile,
and would not be able to be used together with a parametric output
profile.

Co-authored-by: Leandro Ribeiro <leandro.ribeiro@collabora.com>
Signed-off-by: Pekka Paalanen <pekka.paalanen@collabora.com>

frontend/main.c

@@ -1,7 +1,7 @@
 /*
  * Copyright © 2010-2011 Intel Corporation
  * Copyright © 2008-2011 Kristian Høgsberg
- * Copyright © 2012-2018,2022 Collabora, Ltd.
+ * Copyright © 2012-2018,2022-2025 Collabora, Ltd.
  * Copyright © 2010-2011 Benjamin Franzke
  * Copyright © 2013 Jason Ekstrand
  * Copyright © 2017, 2018 General Electric Company
@@ -45,6 +45,7 @@
 #include <libevdev/libevdev.h>
 #include <linux/input.h>
 #include <sys/time.h>
+#include <libdisplay-info/info.h>
 #include <linux/limits.h>
 
 #include "weston.h"
@@ -1353,6 +1354,261 @@ weston_log_indent_multiline(int indent, const char *multiline)
 	}
 }
 
+static struct weston_color_profile *
+wet_create_sRGB_profile(struct weston_compositor *compositor)
+{
+	struct weston_color_profile_param_builder *builder;
+	struct weston_color_profile *cprof;
+	enum weston_color_profile_param_builder_error err_code;
+	char *err_msg = NULL;
+
+	builder = weston_color_profile_param_builder_create(compositor);
+	weston_color_profile_param_builder_set_primaries_named(builder, WESTON_PRIMARIES_CICP_SRGB);
+	weston_color_profile_param_builder_set_tf_named(builder, WESTON_TF_GAMMA22);
+
+	cprof = weston_color_profile_param_builder_create_color_profile(builder, "frontend sRGB",
+									&err_code, &err_msg);
+	if (!cprof) {
+		weston_log("Error: creating parametric sRGB color profile failed:\n");
+		weston_log_indent_multiline(0, err_msg);
+		free(err_msg);
+	}
+
+	return cprof;
+}
+
+static void
+cta861_transfer_function(struct weston_color_profile_param_builder *builder,
+			 enum weston_eotf_mode eotf,
+			 enum weston_colorimetry_mode colorimetry)
+{
+	/* According to CTA-861-I, Table 5 - Colorimetry Transfer Characteristics: */
+
+	switch (eotf) {
+	case WESTON_EOTF_MODE_NONE:
+	case WESTON_EOTF_MODE_SDR:
+	case WESTON_EOTF_MODE_TRADITIONAL_HDR:
+		/* Determined by colorimetry */
+		break;
+	case WESTON_EOTF_MODE_ST2084:
+		weston_color_profile_param_builder_set_tf_named(builder, WESTON_TF_ST2084_PQ);
+		return;
+	case WESTON_EOTF_MODE_HLG:
+		weston_color_profile_param_builder_set_tf_named(builder, WESTON_TF_HLG);
+		return;
+	}
+
+	switch (colorimetry) {
+	case WESTON_COLORIMETRY_MODE_DEFAULT:
+		/* Contrary to CTA-861-I, assume a gamma 2.2 computer monitor. */
+		weston_color_profile_param_builder_set_tf_named(builder, WESTON_TF_GAMMA22);
+		return;
+	case WESTON_COLORIMETRY_MODE_BT2020_CYCC:
+	case WESTON_COLORIMETRY_MODE_BT2020_YCC:
+	case WESTON_COLORIMETRY_MODE_BT2020_RGB:
+		weston_color_profile_param_builder_set_tf_named(builder, WESTON_TF_BT1886);
+		return;
+	case WESTON_COLORIMETRY_MODE_P3D65:
+	case WESTON_COLORIMETRY_MODE_P3DCI:
+		weston_color_profile_param_builder_set_tf_power_exponent(builder, 2.6);
+		return;
+	case WESTON_COLORIMETRY_MODE_ICTCP:
+		/* No TF, reserved combination. */
+	default:
+		break;
+	}
+
+	/* Failed to determine TF. */
+	weston_log("Warning: no known transfer characteristic for the combination of %s and %s.\n",
+		   weston_eotf_mode_to_str(eotf), weston_colorimetry_mode_to_str(colorimetry));
+}
+
+static void
+cta861_primaries(struct weston_color_profile_param_builder *builder,
+		 enum weston_colorimetry_mode colorimetry)
+{
+	switch (colorimetry) {
+	case WESTON_COLORIMETRY_MODE_NONE:
+	case WESTON_COLORIMETRY_MODE_DEFAULT:
+		weston_color_profile_param_builder_set_primaries_named(builder, WESTON_PRIMARIES_CICP_SRGB);
+		break;
+	case WESTON_COLORIMETRY_MODE_BT2020_CYCC:
+	case WESTON_COLORIMETRY_MODE_BT2020_YCC:
+	case WESTON_COLORIMETRY_MODE_BT2020_RGB:
+		weston_color_profile_param_builder_set_primaries_named(builder, WESTON_PRIMARIES_CICP_BT2020);
+		break;
+	case WESTON_COLORIMETRY_MODE_P3D65:
+		weston_color_profile_param_builder_set_primaries_named(builder, WESTON_PRIMARIES_CICP_DISPLAY_P3);
+		break;
+	case WESTON_COLORIMETRY_MODE_P3DCI:
+		weston_color_profile_param_builder_set_primaries_named(builder, WESTON_PRIMARIES_CICP_DCI_P3);
+		break;
+	case WESTON_COLORIMETRY_MODE_ICTCP:
+		weston_color_profile_param_builder_set_primaries_named(builder, WESTON_PRIMARIES_CICP_BT2020);
+		break;
+	}
+}
+
+enum weston_auto_profile_flags {
+	WESTON_EDID_PRIMARIES = 0x01,
+	WESTON_EDID_TF = 0x02,
+	WESTON_EDID_DR = 0x04,
+};
+
+static struct weston_color_profile *
+wet_create_auto_profile(struct weston_output *output, uint32_t flags)
+{
+	enum weston_eotf_mode eotf = weston_output_get_eotf_mode(output);
+	enum weston_colorimetry_mode colorimetry = weston_output_get_colorimetry_mode(output);
+	enum weston_color_profile_param_builder_error err_code;
+	struct weston_head *head;
+	const struct di_info *di_info;
+	struct weston_color_profile_param_builder *builder;
+	struct weston_color_profile *cprof;
+	char *name_part;
+	const char *tf_part = NULL;
+	const char *prim_part = NULL;
+	const char *dr_part = NULL;
+	char *err_msg = NULL;
+	unsigned int i;
+
+	builder = weston_color_profile_param_builder_create(output->compositor);
+
+	/* TODO: handle outputs driving multiple heads. */
+	head = weston_output_get_first_head(output);
+	di_info = weston_head_get_display_info(head);
+
+	if (di_info && (flags & WESTON_EDID_TF) &&
+	    (eotf == WESTON_EOTF_MODE_SDR || eotf == WESTON_EOTF_MODE_TRADITIONAL_HDR)) {
+		float exponent;
+		exponent = di_info_get_default_gamma(di_info);
+		if (exponent != 0.0f) {
+			weston_color_profile_param_builder_set_tf_power_exponent(builder,
+										 exponent);
+			tf_part = "by EDID";
+		}
+	}
+	if (!tf_part) {
+		cta861_transfer_function(builder, eotf, colorimetry);
+		tf_part = "by CTA-861";
+	}
+
+	if (di_info && (flags & WESTON_EDID_PRIMARIES) &&
+	    colorimetry == WESTON_COLORIMETRY_MODE_DEFAULT) {
+		struct weston_color_gamut primaries;
+		const struct di_color_primaries *prim =
+			di_info_get_default_color_primaries(di_info);
+
+		if (prim->has_primaries && prim->has_default_white_point) {
+			for (i = 0; i < 3; i++) {
+				primaries.primary[i].x = prim->primary[i].x;
+				primaries.primary[i].y = prim->primary[i].y;
+			}
+			primaries.white_point.x = prim->default_white.x;
+			primaries.white_point.y = prim->default_white.y;
+
+			weston_color_profile_param_builder_set_primaries(builder, &primaries);
+			prim_part = "by EDID";
+		}
+	}
+	if (!prim_part) {
+		cta861_primaries(builder, colorimetry);
+		prim_part = "by CTA-861";
+	}
+
+	if (di_info && (flags & WESTON_EDID_DR) &&
+	    eotf == WESTON_EOTF_MODE_ST2084) {
+		float min_lum;
+		float max_lum;
+		float max_fall;
+		const struct di_hdr_static_metadata *hdr =
+			di_info_get_hdr_static_metadata(di_info);
+
+		min_lum = hdr->desired_content_min_luminance;
+		max_lum = hdr->desired_content_max_luminance;
+		max_fall = hdr->desired_content_max_frame_avg_luminance;
+
+		if (min_lum != 0.0f && max_lum != 0.0f && max_fall != 0.0f) {
+			weston_color_profile_param_builder_set_target_luminance(builder,
+										min_lum, max_lum);
+			weston_color_profile_param_builder_set_maxFALL(builder, max_fall);
+			dr_part = "by EDID";
+		}
+	}
+	if (!dr_part)
+		dr_part = "no DR info";
+
+	str_printf(&name_part, "output %s automatic, TF: %s, primaries: %s, dr: %s",
+			       output->name, tf_part, prim_part, dr_part);
+
+	cprof = weston_color_profile_param_builder_create_color_profile(builder, name_part,
+									&err_code, &err_msg);
+	if (!cprof) {
+		weston_log("Error: creating parametric color profile failed:\n");
+		weston_log_indent_multiline(0, err_msg);
+		free(err_msg);
+	}
+
+	free(name_part);
+	return cprof;
+}
+
+#define COLOR_PROF_NAME "color-profile"
+
+static struct weston_color_profile *
+wet_parse_auto_profile(struct weston_output *output,
+		       const char *flagstr)
+{
+	static const struct weston_enum_map flagmap[] = {
+		{ "edid-primaries", WESTON_EDID_PRIMARIES },
+		{ "edid-tf", WESTON_EDID_TF },
+		{ "edid-dr", WESTON_EDID_DR },
+	};
+	struct weston_string_array flagarr;
+	uint32_t flags = 0;
+	bool ok = true;
+	size_t i;
+
+	flagarr = weston_parse_space_separated_list(flagstr);
+	for (i = 0; i < flagarr.len; i++) {
+		const struct weston_enum_map *entry;
+		const char *item = flagarr.array[i];
+
+		entry = weston_enum_map_find_name(flagmap, item);
+		if (entry) {
+			flags |= entry->value;
+		} else {
+			weston_log("Config error in weston.ini, output %s, key "
+				   COLOR_PROF_NAME "=auto: invalid flag '%s'.\n",
+				   output->name, item);
+			ok = false;
+		}
+	}
+	weston_string_array_fini(&flagarr);
+
+	if (ok)
+		return wet_create_auto_profile(output, flags);
+	else
+		return NULL;
+}
+
+static struct weston_color_profile *
+wet_create_output_color_profile(struct weston_output *output,
+				struct weston_config *wc,
+				const char *prof_name)
+{
+	if (strcmp(prof_name, "srgb:") == 0)
+		return wet_create_sRGB_profile(output->compositor);
+
+	if (strncmp(prof_name, "auto:", 5) == 0)
+		return wet_parse_auto_profile(output, prof_name + 5);
+
+	weston_log("Config error in weston.ini, output %s, key "
+		   COLOR_PROF_NAME ": invalid value (%s)\n.",
+		   output->name, prof_name);
+	return NULL;
+}
+
 static int
 wet_output_set_vrr_mode(struct weston_output *output,
 			struct weston_config_section *section)
@@ -1442,10 +1698,12 @@ out:
 static int
 wet_output_set_color_profile(struct weston_output *output,
 			     struct weston_config_section *section,
+			     struct weston_config *wc,
 			     struct weston_color_profile *parent_winsys_profile)
 {
 	struct wet_compositor *compositor = to_wet_compositor(output->compositor);
 	struct weston_color_profile *cprof;
+	char *prof_name = NULL;
 	char *icc_file = NULL;
 	char *details;
 	bool ok;
@@ -1454,13 +1712,25 @@ wet_output_set_color_profile(struct weston_output *output,
 		return 0;
 
 	weston_config_section_get_string(section, "icc_profile", &icc_file, NULL);
+	if (!icc_file)
+		weston_config_section_get_string(section, COLOR_PROF_NAME, &prof_name, NULL);
+
 	if (icc_file) {
 		cprof = weston_compositor_load_icc_file(output->compositor,
 							icc_file);
 		free(icc_file);
+	} else if (prof_name) {
+		cprof = wet_create_output_color_profile(output, wc, prof_name);
+		free(prof_name);
 	} else if (parent_winsys_profile) {
 		cprof = weston_color_profile_ref(parent_winsys_profile);
 	} else {
+		/*
+		 * TODO: Once parametric color profiles are fully supported
+		 * and interoperable with ICC profiles, the default profile
+		 * would be created like this:
+		 * cprof = wet_create_output_color_profile(output, wc, "auto:");
+		 */
 		return 0;
 	}
 
@@ -1954,7 +2224,7 @@ wet_configure_windowed_output_from_config(struct weston_output *output,
 		return -1;
 	}
 
-	if (wet_output_set_color_profile(output, section, NULL) < 0)
+	if (wet_output_set_color_profile(output, section, wc, NULL) < 0)
 		return -1;
 
 	if (wet_output_set_color_effect(output, section) < 0)
@@ -2473,9 +2743,6 @@ drm_backend_output_configure(struct weston_output *output,
 		return -1;
 	}
 
-	if (wet_output_set_color_profile(output, section, NULL) < 0)
-		return -1;
-
 	if (wet_output_set_color_effect(output, section) < 0)
 		return -1;
 
@@ -2502,6 +2769,8 @@ drm_backend_output_configure(struct weston_output *output,
 		return -1;
 	if (wet_output_set_colorimetry_mode(output, section, wet->use_color_manager) < 0)
 		return -1;
+	if (wet_output_set_color_profile(output, section, wet->config, NULL) < 0)
+		return -1;
 
 	if (wet_output_set_color_characteristics(output,
 						 wet->config, section) < 0)
@@ -3141,6 +3410,7 @@ drm_backend_remoted_output_configure(struct weston_output *output,
 				     char *modeline,
 				     const struct weston_remoting_api *api)
 {
+	struct weston_config *wc = wet_get_config(output->compositor);
 	char *gbm_format = NULL;
 	char *seat = NULL;
 	char *host = NULL;
@@ -3162,7 +3432,7 @@ drm_backend_remoted_output_configure(struct weston_output *output,
 		return -1;
 	};
 
-	if (wet_output_set_color_profile(output, section, NULL) < 0)
+	if (wet_output_set_color_profile(output, section, wc, NULL) < 0)
 		return -1;
 
 	if (wet_output_set_color_effect(output, section) < 0)
@@ -3307,6 +3577,7 @@ drm_backend_pipewire_output_configure(struct weston_output *output,
 				     char *modeline,
 				     const struct weston_pipewire_api *api)
 {
+	struct weston_config *wc = wet_get_config(output->compositor);
 	char *seat = NULL;
 	int ret;
 
@@ -3325,7 +3596,7 @@ drm_backend_pipewire_output_configure(struct weston_output *output,
 		return -1;
 	}
 
-	if (wet_output_set_color_profile(output, section, NULL) < 0)
+	if (wet_output_set_color_profile(output, section, wc, NULL) < 0)
 		return -1;
 
 	if (wet_output_set_color_effect(output, section) < 0)

frontend/meson.build

@@ -16,6 +16,7 @@ deps_weston = [
 	dep_libevdev,
 	dep_libdl,
 	dep_threads,
+	dep_libdisplay_info,
 ]
 
 if get_option('xwayland')

man/weston.ini.man

@@ -586,6 +586,89 @@ is true, load the given ICC file as the output color profile. This works only
 on DRM, headless, wayland, and x11 backends, and for remoting and pipewire
 outputs.
 .TP 7
+.BI "color-profile=" name
+
+.B NOTE:
+This feature is not fully implemented yet, and therefore it is not expected to
+work.
+
+Color profiles describe how the display is assumed to behave. Knowing the
+display color behavior, Weston can adapt window contents to produce the
+presumed appearance. The option
+.B color-management
+must be set to true for this to work. This works only on DRM, headless,
+wayland, and x11 backends, and for remoting and pipewire outputs. If
+.B icc_profile
+is also set, that is used instead.
+
+This key creates a parametric profile to be used as the output color profile.
+This key can use one of the special profile names that
+contain a colon (:).
+
+The default, once implemented, will be
+.BR "color-profile=auto:" .
+
+The following special names are accepted:
+.RS 11
+.TP
+.B "srgb:"
+Creates a parametric sRGB color profile (gamma 2.2).
+.TP
+.BI  "auto:" "[flags...]"
+Creates an automatic parametric color profile.
+.RE
+
+.IP
+Automatic parametric color profiles are created based on the
+.BR eotf-mode " and " colorimetry-mode
+configuration keys of the respective
+.B output
+section, and optionally using the monitor reported EDID (DRM-backend only).
+Multiple flags must be separated by whitespace. The available flags are:
+.RS 11
+.TP
+.B edid-primaries
+Get primaries and white point from EDID if
+.BR colorimetry-mode " is " default .
+Ignored if EDID does not provide all of them.
+
+.TP
+.B edid-tf
+Get transfer function from EDID if
+.BR eoft-mode " is " sdr " or " hdr-gamma .
+The transfer function is the power-law curve with the EDID indicated exponent.
+
+.TP
+.B edid-dr
+Get dynamic range information from EDID if
+.BR eotf-mode " is " st2084 .
+.RE
+
+.IP
+Examples:
+.RS 11
+.EX
+.B color-profile=srgb:
+.B color-profile=auto:
+.B color-profile=auto:edid-tf edid-dr
+.B color-profile=auto: edid-primaries
+.EE
+.RE
+
+.IP
+Notably, setting
+
+.RS 11
+.EX
+.B eotf-mode=sdr
+.B colorimetry-mode=default
+.B color-profile=auto:
+.EE
+.RE
+.IP
+produces the same color profile as
+.BR color-profile=srgb: .
+.TP 7
 .BI "color-effect=" name
 Use the given color effect for the output. For now we only provide color effects
 for color vision deficiencies (CVD). Only works when option