color: introduce weston_color_profile

Roughly speaking, a color profile describes the color space of content
or an output. Under the hood, the description includes one or more ways
to map colors between the profile space and some standard profile
connecting space (PCS).

This object is not called a color space. A color space has a unique
definition, while a color profile may contain multiple different
mappings depending on render intent. Some of these mappings may be
subjective, with an artistic touch.

When a source color profile and a destination color profile are combined
under a specific render intent, they produce a color transformation.
Color transformations are already preresented by weston_color_transform.

This patch adds the basic API for color profile objects. Everything
worthwhile of these objects is implemented in the color managers:
color-noop never creates these, and in color-lcms they are basically a
container for cmsHPROFILE, the Little CMS object for color profiles.
Color profile objects will not be interpreted outside of the color
managers, unlike color transformations.

For a start, the color manager API has one function to create color
profiles: from ICC profile data. More creation functions for other
sources will be added later.

The API has errmsg return parameter for error messages. These are not
simply weston_log()'d, because CM&HDR protocol will allow clients to
trigger errors and the protocol handles that gracefully. Therefore
instead of flooding the compositor logs, the error messages will
probably need to be relayed back to clients.

Color-lcms is expected to create a cmsHPROFILE for all kinds of color
profiles, not just for those created from ICC profile data. Hence,
color-lcms will fingerprint color profiles by the MD5 hash which Little
CMS computes for us. The fingerprint is used for de-duplication: instead
of creating copies, reference existing color profiles.

This code is very much based on Sebastian Wick's earlier work on Weston
color management, but structured and named differently.

Co-authored-by: Sebastian Wick <sebastian@sebastianwick.net>
Signed-off-by: Pekka Paalanen <pekka.paalanen@collabora.com>

include/libweston/libweston.h

@@ -79,6 +79,7 @@ struct linux_dmabuf_buffer;
 struct weston_recorder;
 struct weston_pointer_constraint;
 struct ro_anonymous_file;
+struct weston_color_profile;
 struct weston_color_transform;
 
 enum weston_keyboard_modifier {
@@ -2126,6 +2127,15 @@ void
 weston_timeline_refresh_subscription_objects(struct weston_compositor *wc,
 					     void *object);
 
+struct weston_color_profile *
+weston_color_profile_ref(struct weston_color_profile *cprof);
+
+void
+weston_color_profile_unref(struct weston_color_profile *cprof);
+
+const char *
+weston_color_profile_get_description(struct weston_color_profile *cprof);
+
 #ifdef  __cplusplus
 }
 #endif

libweston/color-lcms/color-lcms.c

@@ -159,6 +159,7 @@ cmlcms_destroy(struct weston_color_manager *cm_base)
 	struct weston_color_manager_lcms *cm = get_cmlcms(cm_base);
 
 	assert(wl_list_empty(&cm->color_transform_list));
+	assert(wl_list_empty(&cm->color_profile_list));
 
 	cmsDeleteContext(cm->lcms_ctx);
 	free(cm);
@@ -178,6 +179,8 @@ weston_color_manager_create(struct weston_compositor *compositor)
 	cm->base.supports_client_protocol = true;
 	cm->base.init = cmlcms_init;
 	cm->base.destroy = cmlcms_destroy;
+	cm->base.destroy_color_profile = cmlcms_destroy_color_profile;
+	cm->base.get_color_profile_from_icc = cmlcms_get_color_profile_from_icc;
 	cm->base.destroy_color_transform = cmlcms_destroy_color_transform;
 	cm->base.get_surface_color_transform =
 	      cmlcms_get_surface_color_transform;
@@ -188,6 +191,7 @@ weston_color_manager_create(struct weston_compositor *compositor)
 	      cmlcms_get_sRGB_to_blend_color_transform;
 
 	wl_list_init(&cm->color_transform_list);
+	wl_list_init(&cm->color_profile_list);
 
 	return &cm->base;
 }

libweston/color-lcms/color-lcms.h

@@ -38,6 +38,7 @@ struct weston_color_manager_lcms {
 	cmsContext lcms_ctx;
 
 	struct wl_list color_transform_list; /* cmlcms_color_transform::link */
+	struct wl_list color_profile_list; /* cmlcms_color_profile::link */
 };
 
 static inline struct weston_color_manager_lcms *
@@ -46,6 +47,37 @@ get_cmlcms(struct weston_color_manager *cm_base)
 	return container_of(cm_base, struct weston_color_manager_lcms, base);
 }
 
+struct cmlcms_md5_sum {
+	uint8_t bytes[16];
+};
+
+struct cmlcms_color_profile {
+	struct weston_color_profile base;
+
+	/* struct weston_color_manager_lcms::color_profile_list */
+	struct wl_list link;
+
+	cmsHPROFILE profile;
+	struct cmlcms_md5_sum md5sum;
+};
+
+static inline struct cmlcms_color_profile *
+get_cprof(struct weston_color_profile *cprof_base)
+{
+	return container_of(cprof_base, struct cmlcms_color_profile, base);
+}
+
+bool
+cmlcms_get_color_profile_from_icc(struct weston_color_manager *cm,
+				  const void *icc_data,
+				  size_t icc_len,
+				  const char *name_part,
+				  struct weston_color_profile **cprof_out,
+				  char **errmsg);
+
+void
+cmlcms_destroy_color_profile(struct weston_color_profile *cprof_base);
+
 /*
  * Perhaps a placeholder, until we get actual color spaces involved and
  * see how this would work better.

libweston/color-lcms/color-profile.c

@@ -0,0 +1,202 @@
+/*
+ * Copyright 2019 Sebastian Wick
+ * Copyright 2021 Collabora, Ltd.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining
+ * a copy of this software and associated documentation files (the
+ * "Software"), to deal in the Software without restriction, including
+ * without limitation the rights to use, copy, modify, merge, publish,
+ * distribute, sublicense, and/or sell copies of the Software, and to
+ * permit persons to whom the Software is furnished to do so, subject to
+ * the following conditions:
+ *
+ * The above copyright notice and this permission notice (including the
+ * next paragraph) shall be included in all copies or substantial
+ * portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+ * NONINFRINGEMENT.  IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
+ * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
+ * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+#include "config.h"
+
+#include <assert.h>
+#include <stdio.h>
+#include <string.h>
+#include <libweston/libweston.h>
+
+#include "color.h"
+#include "color-lcms.h"
+#include "shared/helpers.h"
+#include "shared/string-helpers.h"
+
+/* FIXME: sync with spec! */
+static bool
+validate_icc_profile(cmsHPROFILE profile, char **errmsg)
+{
+	cmsColorSpaceSignature cs = cmsGetColorSpace(profile);
+	uint32_t nr_channels = cmsChannelsOf(cs);
+	uint8_t version = cmsGetEncodedICCversion(profile) >> 24;
+
+	if (version != 2 && version != 4) {
+		str_printf(errmsg,
+			   "ICC profile major version %d is unsupported, should be 2 or 4.",
+			   version);
+		return false;
+	}
+
+	if (nr_channels != 3) {
+		str_printf(errmsg,
+			   "ICC profile must contain 3 channels for the color space, not %u.",
+			   nr_channels);
+		return false;
+	}
+
+	if (cmsGetDeviceClass(profile) != cmsSigDisplayClass) {
+		str_printf(errmsg, "ICC profile is required to be of Display device class, but it is not.");
+		return false;
+	}
+
+	return true;
+}
+
+static struct cmlcms_color_profile *
+cmlcms_find_color_profile_by_md5(const struct weston_color_manager_lcms *cm,
+				 const struct cmlcms_md5_sum *md5sum)
+{
+	struct cmlcms_color_profile *cprof;
+
+	wl_list_for_each(cprof, &cm->color_profile_list, link) {
+		if (memcmp(cprof->md5sum.bytes,
+			   md5sum->bytes, sizeof(md5sum->bytes)) == 0)
+			return cprof;
+	}
+
+	return NULL;
+}
+
+static struct cmlcms_color_profile *
+cmlcms_color_profile_create(struct weston_color_manager_lcms *cm,
+			    cmsHPROFILE profile,
+			    char *desc,
+			    char **errmsg)
+{
+	struct cmlcms_color_profile *cprof;
+
+	cprof = zalloc(sizeof *cprof);
+	if (!cprof)
+		return NULL;
+
+	weston_color_profile_init(&cprof->base, &cm->base);
+	cprof->base.description = desc;
+	cprof->profile = profile;
+	cmsGetHeaderProfileID(profile, cprof->md5sum.bytes);
+	wl_list_insert(&cm->color_profile_list, &cprof->link);
+
+	return cprof;
+}
+
+static void
+cmlcms_color_profile_destroy(struct cmlcms_color_profile *cprof)
+{
+	wl_list_remove(&cprof->link);
+	cmsCloseProfile(cprof->profile);
+	free(cprof->base.description);
+	free(cprof);
+}
+
+static char *
+make_icc_file_description(cmsHPROFILE profile,
+			  const struct cmlcms_md5_sum *md5sum,
+			  const char *name_part)
+{
+	char md5sum_str[sizeof(md5sum->bytes) * 2 + 1];
+	char *desc;
+	size_t i;
+
+	for (i = 0; i < sizeof(md5sum->bytes); i++) {
+		snprintf(md5sum_str + 2 * i, sizeof(md5sum_str) - 2 * i,
+			 "%02x", md5sum->bytes[i]);
+	}
+
+	str_printf(&desc, "ICCv%f %s %s", cmsGetProfileVersion(profile),
+		   name_part, md5sum_str);
+
+	return desc;
+}
+
+bool
+cmlcms_get_color_profile_from_icc(struct weston_color_manager *cm_base,
+				  const void *icc_data,
+				  size_t icc_len,
+				  const char *name_part,
+				  struct weston_color_profile **cprof_out,
+				  char **errmsg)
+{
+	struct weston_color_manager_lcms *cm = get_cmlcms(cm_base);
+	cmsHPROFILE profile;
+	struct cmlcms_md5_sum md5sum;
+	struct cmlcms_color_profile *cprof;
+	char *desc = NULL;
+
+	if (!icc_data || icc_len < 1) {
+		str_printf(errmsg, "No ICC data.");
+		return false;
+	}
+	if (icc_len >= UINT32_MAX) {
+		str_printf(errmsg, "Too much ICC data.");
+		return false;
+	}
+
+	profile = cmsOpenProfileFromMemTHR(cm->lcms_ctx, icc_data, icc_len);
+	if (!profile) {
+		str_printf(errmsg, "ICC data not understood.");
+		return false;
+	}
+
+	if (!validate_icc_profile(profile, errmsg))
+		goto err_close;
+
+	if (!cmsMD5computeID(profile)) {
+		str_printf(errmsg, "Failed to compute MD5 for ICC profile.");
+		goto err_close;
+	}
+
+	cmsGetHeaderProfileID(profile, md5sum.bytes);
+	cprof = cmlcms_find_color_profile_by_md5(cm, &md5sum);
+	if (cprof) {
+		*cprof_out = weston_color_profile_ref(&cprof->base);
+		cmsCloseProfile(profile);
+		return true;
+	}
+
+	desc = make_icc_file_description(profile, &md5sum, name_part);
+	if (!desc)
+		goto err_close;
+
+	cprof = cmlcms_color_profile_create(cm, profile, desc, errmsg);
+	if (!cprof)
+		goto err_close;
+
+	*cprof_out = &cprof->base;
+	return true;
+
+err_close:
+	free(desc);
+	cmsCloseProfile(profile);
+	return false;
+}
+
+void
+cmlcms_destroy_color_profile(struct weston_color_profile *cprof_base)
+{
+	struct cmlcms_color_profile *cprof = get_cprof(cprof_base);
+
+	cmlcms_color_profile_destroy(cprof);
+}

libweston/color-lcms/meson.build

@@ -9,6 +9,7 @@ endif
 
 srcs_color_lcms = [
 	'color-lcms.c',
+	'color-profile.c',
 	'color-transform.c',
 ]
 

libweston/color-noop.c

@@ -29,6 +29,7 @@
 
 #include "color.h"
 #include "shared/helpers.h"
+#include "shared/string-helpers.h"
 
 struct weston_color_manager_noop {
 	struct weston_color_manager base;
@@ -40,6 +41,24 @@ get_cmnoop(struct weston_color_manager *cm_base)
 	return container_of(cm_base, struct weston_color_manager_noop, base);
 }
 
+static void
+cmnoop_destroy_color_profile(struct weston_color_profile *cprof)
+{
+	/* Never called, as never creates an actual color profile. */
+}
+
+static bool
+cmnoop_get_color_profile_from_icc(struct weston_color_manager *cm,
+				  const void *icc_data,
+				  size_t icc_len,
+				  const char *name_part,
+				  struct weston_color_profile **cprof_out,
+				  char **errmsg)
+{
+	str_printf(errmsg, "ICC profiles are unsupported.");
+	return false;
+}
+
 static void
 cmnoop_destroy_color_transform(struct weston_color_transform *xform)
 {
@@ -131,6 +150,8 @@ weston_color_manager_noop_create(struct weston_compositor *compositor)
 	cm->base.supports_client_protocol = false;
 	cm->base.init = cmnoop_init;
 	cm->base.destroy = cmnoop_destroy;
+	cm->base.destroy_color_profile = cmnoop_destroy_color_profile;
+	cm->base.get_color_profile_from_icc = cmnoop_get_color_profile_from_icc;
 	cm->base.destroy_color_transform = cmnoop_destroy_color_transform;
 	cm->base.get_surface_color_transform =
 	      cmnoop_get_surface_color_transform;

libweston/color.c

@@ -31,6 +31,77 @@
 #include "color.h"
 #include "libweston-internal.h"
 
+/**
+ * Increase reference count of the color profile object
+ *
+ * \param cprof The color profile. NULL is accepted too.
+ * \return cprof.
+ */
+WL_EXPORT struct weston_color_profile *
+weston_color_profile_ref(struct weston_color_profile *cprof)
+{
+	/* NULL is a valid color space: sRGB */
+	if (!cprof)
+		return NULL;
+
+	assert(cprof->ref_count > 0);
+	cprof->ref_count++;
+	return cprof;
+}
+
+/**
+ * Decrease reference count and potentially destroy the color profile object
+ *
+ * \param cprof The color profile. NULL is accepted too.
+ */
+WL_EXPORT void
+weston_color_profile_unref(struct weston_color_profile *cprof)
+{
+	if (!cprof)
+		return;
+
+	assert(cprof->ref_count > 0);
+	if (--cprof->ref_count > 0)
+		return;
+
+	cprof->cm->destroy_color_profile(cprof);
+}
+
+/**
+ * Get color profile description
+ *
+ * A description of the profile is meant for human readable logs.
+ *
+ * \param cprof The color profile, NULL is accepted too.
+ * \returns The color profile description, valid as long as the
+ * color profile itself is.
+ */
+WL_EXPORT const char *
+weston_color_profile_get_description(struct weston_color_profile *cprof)
+{
+	if (cprof)
+		return cprof->description;
+	else
+		return "built-in default sRGB SDR profile";
+}
+
+/**
+ * Initializes a newly allocated color profile object
+ *
+ * This is used only by color managers. They sub-class weston_color_profile.
+ *
+ * The reference count starts at 1.
+ *
+ * To destroy a weston_color_profile, use weston_color_profile_unref().
+ */
+WL_EXPORT void
+weston_color_profile_init(struct weston_color_profile *cprof,
+			  struct weston_color_manager *cm)
+{
+	cprof->cm = cm;
+	cprof->ref_count = 1;
+}
+
 /**
  * Increase reference count of the color transform object
  *

libweston/color.h

@@ -27,8 +27,20 @@
 #define WESTON_COLOR_H
 
 #include <stdbool.h>
+#include <stdint.h>
 #include <libweston/libweston.h>
 
+/**
+ * Represents a color profile description (an ICC color profile)
+ *
+ * Sub-classed by the color manager that created this.
+ */
+struct weston_color_profile {
+	struct weston_color_manager *cm;
+	int ref_count;
+	char *description;
+};
+
 /** Type or formula for a curve */
 enum weston_color_curve_type {
 	/** Identity function, no-op */
@@ -161,6 +173,35 @@ struct weston_color_manager {
 	void
 	(*destroy)(struct weston_color_manager *cm);
 
+	/** Destroy a color profile after refcount fell to zero */
+	void
+	(*destroy_color_profile)(struct weston_color_profile *cprof);
+
+	/** Create a color profile from ICC data
+	 *
+	 * \param cm The color manager.
+	 * \param icc_data Pointer to the ICC binary data.
+	 * \param icc_len Length of the ICC data in bytes.
+	 * \param name_part A string to be used in describing the profile.
+	 * \param cprof_out On success, the created object is returned here.
+	 * On failure, untouched.
+	 * \param errmsg On success, untouched. On failure, a pointer to a
+	 * string describing the error is stored here. The string must be
+	 * free()'d.
+	 * \return True on success, false on failure.
+	 *
+	 * This may return a new reference to an existing color profile if
+	 * that profile is identical to the one that would be created, apart
+	 * from name_part.
+	 */
+	bool
+	(*get_color_profile_from_icc)(struct weston_color_manager *cm,
+				      const void *icc_data,
+				      size_t icc_len,
+				      const char *name_part,
+				      struct weston_color_profile **cprof_out,
+				      char **errmsg);
+
 	/** Destroy a color transform after refcount fell to zero */
 	void
 	(*destroy_color_transform)(struct weston_color_transform *xform);
@@ -231,6 +272,10 @@ struct weston_color_manager {
 					     struct weston_color_transform **xform_out);
 };
 
+void
+weston_color_profile_init(struct weston_color_profile *cprof,
+			  struct weston_color_manager *cm);
+
 struct weston_color_transform *
 weston_color_transform_ref(struct weston_color_transform *xform);