Prepare for parallelized colour management

This rewrite is more or less necessary for:
 - colour-managed browser thumbnails,
 - asynchronous image loading,
 - turning fiv-io into a reusable library.

Little CMS has a fairly terrible API in this regard.

7 files changed, 347 insertions, 236 deletions

diff --git a/fiv-io-profile.c b/fiv-io-cmm.c
index 2c6f345..b131acf 100644
--- a/fiv-io-profile.c
+++ b/fiv-io-cmm.c
@@ -1,5 +1,5 @@
 //
-// fiv-profile.c: colour management
+// fiv-io-cmm.c: colour management
 //
 // Copyright (c) 2024, Přemysl Eric Janouch <p@janouch.name>
 //
@@ -23,6 +23,7 @@
 #include "fiv-io.h"
 
 // Colour management must be handled before RGB conversions.
+// TODO(p): Make it also possible to use Skia's skcms.
 #ifdef HAVE_LCMS2
 #include <lcms2.h>
 #endif  // HAVE_LCMS2
@@ -30,48 +31,176 @@
 #include <lcms2_fast_float.h>
 #endif  // HAVE_LCMS2_FAST_FLOAT
 
-// https://github.com/mm2/Little-CMS/issues/430
-static bool g_broken_cms_premul;
+// --- CMM-independent transforms ----------------------------------------------
+
+// CAIRO_STRIDE_ALIGNMENT is 4 bytes, so there will be no padding with
+// ARGB/BGRA/XRGB/BGRX.
+static void
+trivial_cmyk_to_host_byte_order_argb(unsigned char *p, int len)
+{
+	// This CMYK handling has been seen in gdk-pixbuf/JPEG, GIMP/JPEG, skcms.
+	// It will typically produce horribly oversaturated results.
+	// Assume that all YCCK/CMYK JPEG files use inverted CMYK, as Photoshop
+	// does, see https://bugzilla.gnome.org/show_bug.cgi?id=618096
+	while (len--) {
+		int c = p[0], m = p[1], y = p[2], k = p[3];
+#if G_BYTE_ORDER == G_LITTLE_ENDIAN
+		p[0] = k * y / 255;
+		p[1] = k * m / 255;
+		p[2] = k * c / 255;
+		p[3] = 255;
+#else
+		p[3] = k * y / 255;
+		p[2] = k * m / 255;
+		p[1] = k * c / 255;
+		p[0] = 255;
+#endif
+		p += 4;
+	}
+}
+
+// From libwebp, verified to exactly match [x * a / 255].
+#define PREMULTIPLY8(a, x) (((uint32_t) (x) * (uint32_t) (a) * 32897U) >> 23)
+
+void
+fiv_io_premultiply_argb32(FivIoImage *image)
+{
+	if (image->format != CAIRO_FORMAT_ARGB32)
+		return;
+
+	for (uint32_t y = 0; y < image->height; y++) {
+		uint32_t *dstp = (uint32_t *) (image->data + image->stride * y);
+		for (uint32_t x = 0; x < image->width; x++) {
+			uint32_t argb = dstp[x], a = argb >> 24;
+			dstp[x] = a << 24 |
+				PREMULTIPLY8(a, 0xFF & (argb >> 16)) << 16 |
+				PREMULTIPLY8(a, 0xFF & (argb >>  8)) <<  8 |
+				PREMULTIPLY8(a, 0xFF &  argb);
+		}
+	}
+}
+
+// --- Profiles ----------------------------------------------------------------
+#ifdef HAVE_LCMS2
+
+struct _FivIoProfile {
+	FivIoCmm *cmm;
+	cmsHPROFILE profile;
+};
+
+GBytes *
+fiv_io_profile_to_bytes(FivIoProfile *profile)
+{
+	cmsUInt32Number len = 0;
+	(void) cmsSaveProfileToMem(profile, NULL, &len);
+	gchar *data = g_malloc0(len);
+	if (!cmsSaveProfileToMem(profile, data, &len)) {
+		g_free(data);
+		return NULL;
+	}
+	return g_bytes_new_take(data, len);
+}
+
+static FivIoProfile *
+fiv_io_profile_new(FivIoCmm *cmm, cmsHPROFILE profile)
+{
+	FivIoProfile *self = g_new0(FivIoProfile, 1);
+	self->cmm = g_object_ref(cmm);
+	self->profile = profile;
+	return self;
+}
 
 void
-fiv_io_profile_init(void)
+fiv_io_profile_free(FivIoProfile *self)
+{
+	cmsCloseProfile(self->profile);
+	g_clear_object(&self->cmm);
+	g_free(self);
+}
+
+#else  // ! HAVE_LCMS2
+
+GBytes *fiv_io_profile_to_bytes(FivIoProfile *) { return NULL; }
+void fiv_io_profile_free(FivIoProfile *) {}
+
+#endif  // ! HAVE_LCMS2
+// --- Contexts ----------------------------------------------------------------
+#ifdef HAVE_LCMS2
+
+struct _FivIoCmm {
+	GObject parent_instance;
+	cmsContext context;
+
+	// https://github.com/mm2/Little-CMS/issues/430
+	gboolean broken_premul;
+};
+
+G_DEFINE_TYPE(FivIoCmm, fiv_io_cmm, G_TYPE_OBJECT)
+
+static void
+fiv_io_cmm_finalize(GObject *gobject)
+{
+	FivIoCmm *self = FIV_IO_CMM(gobject);
+	cmsDeleteContext(self->context);
+
+	G_OBJECT_CLASS(fiv_io_cmm_parent_class)->finalize(gobject);
+}
+
+static void
+fiv_io_cmm_class_init(FivIoCmmClass *klass)
+{
+	GObjectClass *object_class = G_OBJECT_CLASS(klass);
+	object_class->finalize = fiv_io_cmm_finalize;
+}
+
+static void
+fiv_io_cmm_init(FivIoCmm *self)
 {
-	// TODO(p): Use Little CMS with contexts instead.
+	self->context = cmsCreateContext(NULL, self);
 #ifdef HAVE_LCMS2_FAST_FLOAT
-	if (cmsPluginTHR(NULL, cmsFastFloatExtensions()))
-		g_broken_cms_premul = LCMS_VERSION <= 2160;
+	if (cmsPluginTHR(self->context, cmsFastFloatExtensions()))
+		self->broken_premul = LCMS_VERSION <= 2160;
 #endif  // HAVE_LCMS2_FAST_FLOAT
 }
 
+// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+
+FivIoCmm *
+fiv_io_cmm_get_default(void)
+{
+	static gsize initialization_value = 0;
+	static FivIoCmm *default_ = NULL;
+	if (g_once_init_enter(&initialization_value)) {
+		gsize setup_value = 1;
+		default_ = g_object_new(FIV_TYPE_IO_CMM, NULL);
+		g_once_init_leave(&initialization_value, setup_value);
+	}
+	return default_;
+}
+
 FivIoProfile *
-fiv_io_profile_new(const void *data, size_t len)
+fiv_io_cmm_get_profile(FivIoCmm *self, const void *data, size_t len)
 {
-#ifdef HAVE_LCMS2
-	return cmsOpenProfileFromMemTHR(NULL, data, len);
-#else
-	(void) data;
-	(void) len;
-	return NULL;
-#endif
+	g_return_val_if_fail(self != NULL, NULL);
+
+	return fiv_io_profile_new(self,
+		cmsOpenProfileFromMemTHR(self->context, data, len));
 }
 
 FivIoProfile *
-fiv_io_profile_new_sRGB(void)
+fiv_io_cmm_get_profile_sRGB(FivIoCmm *self)
 {
-#ifdef HAVE_LCMS2
-	return cmsCreate_sRGBProfileTHR(NULL);
-#else
-	return NULL;
-#endif
+	g_return_val_if_fail(self != NULL, NULL);
+
+	return fiv_io_profile_new(self,
+		cmsCreate_sRGBProfileTHR(self->context));
 }
 
 FivIoProfile *
-fiv_io_profile_new_parametric(
+fiv_io_cmm_get_profile_parametric(FivIoCmm *self,
 	double gamma, double whitepoint[2], double primaries[6])
 {
-#ifdef HAVE_LCMS2
-	// TODO(p): Make sure to use the library in a thread-safe manner.
-	cmsContext context = NULL;
+	g_return_val_if_fail(self != NULL, NULL);
 
 	const cmsCIExyY cmsWP = {whitepoint[0], whitepoint[1], 1.0};
 	const cmsCIExyYTRIPLE cmsP = {
@@ -80,117 +209,81 @@ fiv_io_profile_new_parametric(
 		{primaries[4], primaries[5], 1.0},
 	};
 
-	cmsToneCurve *curve = cmsBuildGamma(context, gamma);
+	cmsToneCurve *curve = cmsBuildGamma(self->context, gamma);
 	if (!curve)
 		return NULL;
 
-	cmsHPROFILE profile = cmsCreateRGBProfileTHR(
-		context, &cmsWP, &cmsP, (cmsToneCurve *[3]){curve, curve, curve});
+	cmsHPROFILE profile = cmsCreateRGBProfileTHR(self->context,
+		&cmsWP, &cmsP, (cmsToneCurve *[3]){curve, curve, curve});
 	cmsFreeToneCurve(curve);
-	return profile;
-#else
-	(void) gamma;
-	(void) whitepoint;
-	(void) primaries;
+	return fiv_io_profile_new(self, profile);
+}
+
+#else  // ! HAVE_LCMS2
+
+FivIoCmm *
+fiv_io_cmm_get_default()
+{
 	return NULL;
-#endif
 }
 
 FivIoProfile *
-fiv_io_profile_new_sRGB_gamma(double gamma)
+fiv_io_cmm_get_profile(FivIoCmm *, const void *, size_t)
 {
-	return fiv_io_profile_new_parametric(gamma,
-		(double[2]){0.3127, 0.3290},
-		(double[6]){0.6400, 0.3300, 0.3000, 0.6000, 0.1500, 0.0600});
+	return NULL;
 }
 
 FivIoProfile *
-fiv_io_profile_new_from_bytes(GBytes *bytes)
+fiv_io_cmm_get_profile_sRGB(FivIoCmm *)
 {
-	gsize len = 0;
-	gconstpointer p = g_bytes_get_data(bytes, &len);
-	return fiv_io_profile_new(p, len);
+	return NULL;
 }
 
-GBytes *
-fiv_io_profile_to_bytes(FivIoProfile *profile)
+FivIoProfile *
+fiv_io_cmm_get_profile_parametric(FivIoCmm *, double, double[2], double[6])
 {
-#ifdef HAVE_LCMS2
-	cmsUInt32Number len = 0;
-	(void) cmsSaveProfileToMem(profile, NULL, &len);
-	gchar *data = g_malloc0(len);
-	if (!cmsSaveProfileToMem(profile, data, &len)) {
-		g_free(data);
-		return NULL;
-	}
-	return g_bytes_new_take(data, len);
-#else
-	(void) profile;
 	return NULL;
-#endif
 }
 
-void
-fiv_io_profile_free(FivIoProfile *self)
+#endif  // ! HAVE_LCMS2
+// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+
+FivIoProfile *
+fiv_io_cmm_get_profile_sRGB_gamma(FivIoCmm *self, double gamma)
 {
-#ifdef HAVE_LCMS2
-	cmsCloseProfile(self);
-#else
-	(void) self;
-#endif
+	return fiv_io_cmm_get_profile_parametric(self, gamma,
+		(double[2]){0.3127, 0.3290},
+		(double[6]){0.6400, 0.3300, 0.3000, 0.6000, 0.1500, 0.0600});
+}
+
+FivIoProfile *
+fiv_io_cmm_get_profile_from_bytes(FivIoCmm *self, GBytes *bytes)
+{
+	gsize len = 0;
+	gconstpointer p = g_bytes_get_data(bytes, &len);
+	return fiv_io_cmm_get_profile(self, p, len);
 }
 
 // --- Image loading -----------------------------------------------------------
+#ifdef HAVE_LCMS2
 
 // TODO(p): In general, try to use CAIRO_FORMAT_RGB30 or CAIRO_FORMAT_RGBA128F.
-#ifndef HAVE_LCMS2
-#define FIV_IO_PROFILE_ARGB32 0
-#define FIV_IO_PROFILE_4X16LE 0
-#else
 #define FIV_IO_PROFILE_ARGB32 \
 	(G_BYTE_ORDER == G_LITTLE_ENDIAN ? TYPE_BGRA_8 : TYPE_ARGB_8)
 #define FIV_IO_PROFILE_4X16LE \
 	(G_BYTE_ORDER == G_LITTLE_ENDIAN ? TYPE_BGRA_16 : TYPE_BGRA_16_SE)
-#endif
-
-// CAIRO_STRIDE_ALIGNMENT is 4 bytes, so there will be no padding with
-// ARGB/BGRA/XRGB/BGRX.
-static void
-trivial_cmyk_to_host_byte_order_argb(unsigned char *p, int len)
-{
-	// This CMYK handling has been seen in gdk-pixbuf/JPEG, GIMP/JPEG, skcms.
-	// It will typically produce horribly oversaturated results.
-	// Assume that all YCCK/CMYK JPEG files use inverted CMYK, as Photoshop
-	// does, see https://bugzilla.gnome.org/show_bug.cgi?id=618096
-	while (len--) {
-		int c = p[0], m = p[1], y = p[2], k = p[3];
-#if G_BYTE_ORDER == G_LITTLE_ENDIAN
-		p[0] = k * y / 255;
-		p[1] = k * m / 255;
-		p[2] = k * c / 255;
-		p[3] = 255;
-#else
-		p[3] = k * y / 255;
-		p[2] = k * m / 255;
-		p[1] = k * c / 255;
-		p[0] = 255;
-#endif
-		p += 4;
-	}
-}
 
 void
-fiv_io_profile_cmyk(
+fiv_io_cmm_cmyk(FivIoCmm *self,
 	FivIoImage *image, FivIoProfile *source, FivIoProfile *target)
 {
-#ifndef HAVE_LCMS2
-	(void) source;
-	(void) target;
-#else
+	g_return_if_fail(target == NULL || self != NULL);
+
 	cmsHTRANSFORM transform = NULL;
 	if (source && target) {
-		transform = cmsCreateTransformTHR(NULL, source, TYPE_CMYK_8_REV, target,
-			FIV_IO_PROFILE_ARGB32, INTENT_PERCEPTUAL, 0);
+		transform = cmsCreateTransformTHR(self->context,
+			source->profile, TYPE_CMYK_8_REV,
+			target->profile, FIV_IO_PROFILE_ARGB32, INTENT_PERCEPTUAL, 0);
 	}
 	if (transform) {
 		cmsDoTransform(
@@ -198,129 +291,105 @@ fiv_io_profile_cmyk(
 		cmsDeleteTransform(transform);
 		return;
 	}
-#endif
 	trivial_cmyk_to_host_byte_order_argb(
 		image->data, image->width * image->height);
 }
 
 static bool
-fiv_io_profile_rgb_direct(unsigned char *data, int w, int h,
+fiv_io_cmm_rgb_direct(FivIoCmm *self, unsigned char *data, int w, int h,
 	FivIoProfile *source, FivIoProfile *target,
 	uint32_t source_format, uint32_t target_format)
 {
-#ifndef HAVE_LCMS2
-	(void) data;
-	(void) w;
-	(void) h;
-	(void) source;
-	(void) source_format;
-	(void) target;
-	(void) target_format;
-	return false;
-#else
+	g_return_val_if_fail(target == NULL || self != NULL, false);
+
 	// TODO(p): We should make this optional.
-	cmsHPROFILE src_fallback = NULL;
+	FivIoProfile *src_fallback = NULL;
 	if (target && !source)
-		source = src_fallback = cmsCreate_sRGBProfileTHR(NULL);
+		source = src_fallback = fiv_io_cmm_get_profile_sRGB(self);
 
 	cmsHTRANSFORM transform = NULL;
 	if (source && target) {
-		transform = cmsCreateTransformTHR(NULL,
-			source, source_format, target, target_format, INTENT_PERCEPTUAL, 0);
+		transform = cmsCreateTransformTHR(self->context,
+			source->profile, source_format,
+			target->profile, target_format, INTENT_PERCEPTUAL, 0);
 	}
 	if (transform) {
 		cmsDoTransform(transform, data, data, w * h);
 		cmsDeleteTransform(transform);
 	}
 	if (src_fallback)
-		cmsCloseProfile(src_fallback);
+		fiv_io_profile_free(src_fallback);
 	return transform != NULL;
-#endif
 }
 
 static void
-fiv_io_profile_xrgb32(
+fiv_io_cmm_xrgb32(FivIoCmm *self,
 	FivIoImage *image, FivIoProfile *source, FivIoProfile *target)
 {
-	fiv_io_profile_rgb_direct(image->data, image->width, image->height,
+	fiv_io_cmm_rgb_direct(self, image->data, image->width, image->height,
 		source, target, FIV_IO_PROFILE_ARGB32, FIV_IO_PROFILE_ARGB32);
 }
 
 void
-fiv_io_profile_4x16le_direct(unsigned char *data,
+fiv_io_cmm_4x16le_direct(FivIoCmm *self, unsigned char *data,
 	int w, int h, FivIoProfile *source, FivIoProfile *target)
 {
-	fiv_io_profile_rgb_direct(data, w, h, source, target,
+	fiv_io_cmm_rgb_direct(self, data, w, h, source, target,
 		FIV_IO_PROFILE_4X16LE, FIV_IO_PROFILE_4X16LE);
 }
 
-// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+#else  // ! HAVE_LCMS2
 
 void
-fiv_io_profile_page(FivIoImage *page, FivIoProfile *target,
-	void (*frame_cb) (FivIoImage *, FivIoProfile *, FivIoProfile *))
+fiv_io_cmm_cmyk(FivIoCmm *, FivIoImage *image, FivIoProfile *, FivIoProfile *)
 {
-	FivIoProfile *source = NULL;
-	if (page->icc)
-		source = fiv_io_profile_new_from_bytes(page->icc);
-
-	// TODO(p): All animations need to be composited in a linear colour space.
-	for (FivIoImage *frame = page; frame != NULL; frame = frame->frame_next)
-		frame_cb(frame, source, target);
-
-	if (source)
-		fiv_io_profile_free(source);
+	trivial_cmyk_to_host_byte_order_argb(
+		image->data, image->width * image->height);
 }
 
-// From libwebp, verified to exactly match [x * a / 255].
-#define PREMULTIPLY8(a, x) (((uint32_t) (x) * (uint32_t) (a) * 32897U) >> 23)
+static void
+fiv_io_cmm_xrgb32(FivIoCmm *, FivIoImage *, FivIoProfile *, FivIoProfile *)
+{
+}
 
 void
-fiv_io_premultiply_argb32(FivIoImage *image)
+fiv_io_cmm_4x16le_direct(
+	FivIoCmm *, unsigned char *, int, int, FivIoProfile *, FivIoProfile *)
 {
-	if (image->format != CAIRO_FORMAT_ARGB32)
-		return;
-
-	for (uint32_t y = 0; y < image->height; y++) {
-		uint32_t *dstp = (uint32_t *) (image->data + image->stride * y);
-		for (uint32_t x = 0; x < image->width; x++) {
-			uint32_t argb = dstp[x], a = argb >> 24;
-			dstp[x] = a << 24 |
-				PREMULTIPLY8(a, 0xFF & (argb >> 16)) << 16 |
-				PREMULTIPLY8(a, 0xFF & (argb >>  8)) <<  8 |
-				PREMULTIPLY8(a, 0xFF &  argb);
-		}
-	}
 }
 
+#endif  // ! HAVE_LCMS2
+// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 #if defined HAVE_LCMS2 && LCMS_VERSION >= 2130
 
 #define FIV_IO_PROFILE_ARGB32_PREMUL \
 	(G_BYTE_ORDER == G_LITTLE_ENDIAN ? TYPE_BGRA_8_PREMUL : TYPE_ARGB_8_PREMUL)
 
 static void
-fiv_io_profile_argb32(FivIoImage *image,
+fiv_io_cmm_argb32(FivIoCmm *self, FivIoImage *image,
 	FivIoProfile *source, FivIoProfile *target)
 {
 	g_return_if_fail(image->format == CAIRO_FORMAT_ARGB32);
 
-	// TODO: With g_no_cms_premultiplication,
+	// TODO: With self->broken_premul,
 	// this probably also needs to be wrapped in un-premultiplication.
-	fiv_io_profile_rgb_direct(image->data, image->width, image->height,
+	fiv_io_cmm_rgb_direct(self, image->data, image->width, image->height,
 		source, target,
 		FIV_IO_PROFILE_ARGB32_PREMUL, FIV_IO_PROFILE_ARGB32_PREMUL);
 }
 
 void
-fiv_io_profile_argb32_premultiply(
+fiv_io_cmm_argb32_premultiply(FivIoCmm *self,
 	FivIoImage *image, FivIoProfile *source, FivIoProfile *target)
 {
+	g_return_if_fail(target == NULL || self != NULL);
+
 	if (image->format != CAIRO_FORMAT_ARGB32) {
-		fiv_io_profile_xrgb32(image, source, target);
-	} else if (g_broken_cms_premul) {
-		fiv_io_profile_xrgb32(image, source, target);
+		fiv_io_cmm_xrgb32(self, image, source, target);
+	} else if (!target || self->broken_premul) {
+		fiv_io_cmm_xrgb32(self, image, source, target);
 		fiv_io_premultiply_argb32(image);
-	} else if (!fiv_io_profile_rgb_direct(image->data,
+	} else if (!fiv_io_cmm_rgb_direct(self, image->data,
 			image->width, image->height, source, target,
 			FIV_IO_PROFILE_ARGB32, FIV_IO_PROFILE_ARGB32_PREMUL)) {
 		g_debug("failed to create a premultiplying transform");
@@ -330,23 +399,41 @@ fiv_io_profile_argb32_premultiply(
 
 #else  // ! HAVE_LCMS2 || LCMS_VERSION < 2130
 
-// TODO(p): Unpremultiply, transform, repremultiply. Or require lcms2>=2.13.
-#define fiv_io_profile_argb32(surface, source, target)
-
 static void
-fiv_io_profile_argb32_premultiply(
+fiv_io_cmm_argb32(FivIoCmm *, FivIoImage *, FivIoProfile *, FivIoProfile *)
+{
+	// TODO(p): Unpremultiply, transform, repremultiply. Or require lcms2>=2.13.
+}
+
+void
+fiv_io_cmm_argb32_premultiply(FivIoCmm *self,
 	FivIoImage *image, FivIoProfile *source, FivIoProfile *target)
 {
-	fiv_io_profile_xrgb32(image, source, target);
+	fiv_io_cmm_xrgb32(self, image, source, target);
 	fiv_io_premultiply_argb32(image);
 }
 
 #endif  // ! HAVE_LCMS2 || LCMS_VERSION < 2130
-
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 
 void
-fiv_io_profile_any(
+fiv_io_cmm_page(FivIoCmm *self, FivIoImage *page, FivIoProfile *target,
+	void (*frame_cb) (FivIoCmm *, FivIoImage *, FivIoProfile *, FivIoProfile *))
+{
+	FivIoProfile *source = NULL;
+	if (page->icc)
+		source = fiv_io_cmm_get_profile_from_bytes(self, page->icc);
+
+	// TODO(p): All animations need to be composited in a linear colour space.
+	for (FivIoImage *frame = page; frame != NULL; frame = frame->frame_next)
+		frame_cb(self, frame, source, target);
+
+	if (source)
+		fiv_io_profile_free(source);
+}
+
+void
+fiv_io_cmm_any(FivIoCmm *self,
 	FivIoImage *image, FivIoProfile *source, FivIoProfile *target)
 {
 	// TODO(p): Ensure we do colour management early enough, so that
@@ -354,9 +441,9 @@ fiv_io_profile_any(
 	// and also for correct alpha compositing.
 	switch (image->format) {
 	break; case CAIRO_FORMAT_RGB24:
-		fiv_io_profile_xrgb32(image, source, target);
+		fiv_io_cmm_xrgb32(self, image, source, target);
 	break; case CAIRO_FORMAT_ARGB32:
-		fiv_io_profile_argb32(image, source, target);
+		fiv_io_cmm_argb32(self, image, source, target);
 	break; default:
 		g_debug("CM attempted on an unsupported surface format");
 	}
@@ -364,12 +451,12 @@ fiv_io_profile_any(
 
 // TODO(p): Offer better integration, upgrade the bit depth if appropriate.
 FivIoImage *
-fiv_io_profile_finalize(FivIoImage *image, FivIoProfile *target)
+fiv_io_cmm_finish(FivIoCmm *self, FivIoImage *image, FivIoProfile *target)
 {
 	if (!target)
 		return image;
 
 	for (FivIoImage *page = image; page != NULL; page = page->page_next)
-		fiv_io_profile_page(page, target, fiv_io_profile_any);
+		fiv_io_cmm_page(self, page, target, fiv_io_cmm_any);
 	return image;
 }
diff --git a/fiv-io.c b/fiv-io.c
index ce30f2d..e3d8c12 100644
--- a/fiv-io.c
+++ b/fiv-io.c
@@ -379,6 +379,7 @@ struct load_wuffs_frame_context {
 	GBytes *meta_iccp;                  ///< Reference-counted ICC profile
 	GBytes *meta_xmp;                   ///< Reference-counted XMP
 
+	FivIoCmm *cmm;                      ///< CMM context, if any
 	FivIoProfile *target;               ///< Target device profile, if any
 	FivIoProfile *source;               ///< Source colour profile, if any
 
@@ -447,11 +448,12 @@ load_wuffs_frame(struct load_wuffs_frame_context *ctx, GError **error)
 
 	if (ctx->target) {
 		if (ctx->expand_16_float || ctx->pack_16_10) {
-			fiv_io_profile_4x16le_direct(
+			fiv_io_cmm_4x16le_direct(ctx->cmm,
 				targetbuf, ctx->width, ctx->height, ctx->source, ctx->target);
 			// The first one premultiplies below, the second doesn't need to.
 		} else {
-			fiv_io_profile_argb32_premultiply(image, ctx->source, ctx->target);
+			fiv_io_cmm_argb32_premultiply(
+				ctx->cmm, image, ctx->source, ctx->target);
 		}
 	}
 
@@ -589,7 +591,8 @@ open_wuffs(wuffs_base__image_decoder *dec, wuffs_base__io_buffer src,
 	const FivIoOpenContext *ioctx, GError **error)
 {
 	struct load_wuffs_frame_context ctx = {
-		.dec = dec, .src = &src, .target = ioctx->screen_profile};
+		.dec = dec, .src = &src,
+		.cmm = ioctx->cmm, .target = ioctx->screen_profile};
 
 	// TODO(p): PNG text chunks, like we do with PNG thumbnails.
 	// TODO(p): See if something could and should be done about
@@ -673,9 +676,11 @@ open_wuffs(wuffs_base__image_decoder *dec, wuffs_base__io_buffer src,
 	// TODO(p): Improve our simplistic PNG handling of: gAMA, cHRM, sRGB.
 	if (ctx.target) {
 		if (ctx.meta_iccp)
-			ctx.source = fiv_io_profile_new_from_bytes(ctx.meta_iccp);
+			ctx.source = fiv_io_cmm_get_profile_from_bytes(
+				ctx.cmm, ctx.meta_iccp);
 		else if (isfinite(gamma) && gamma > 0)
-			ctx.source = fiv_io_profile_new_sRGB_gamma(gamma);
+			ctx.source = fiv_io_cmm_get_profile_sRGB_gamma(
+				ctx.cmm, gamma);
 	}
 
 	// Wuffs maps tRNS to BGRA in `decoder.decode_trns?`, we should be fine.
@@ -1059,7 +1064,7 @@ parse_exif_profile_subifd(
 }
 
 static FivIoProfile *
-parse_exif_profile(const void *data, size_t len)
+parse_exif_profile(FivIoCmm *cmm, const void *data, size_t len)
 {
 	struct tiffer T = {};
 	if (!tiffer_init(&T, (const uint8_t *) data, len) || !tiffer_next_ifd(&T))
@@ -1091,7 +1096,7 @@ parse_exif_profile(const void *data, size_t len)
 
 	// If sRGB is claimed, assume all parameters are standard.
 	if (params.colorspace == Exif_ColorSpace_sRGB)
-		return fiv_io_profile_new_sRGB();
+		return fiv_io_cmm_get_profile_sRGB(cmm);
 
 	// AdobeRGB Nikon JPEGs provide all of these.
 	if (params.colorspace != Exif_ColorSpace_Uncalibrated ||
@@ -1100,7 +1105,7 @@ parse_exif_profile(const void *data, size_t len)
 		!params.have_primaries)
 		return NULL;
 
-	return fiv_io_profile_new_parametric(
+	return fiv_io_cmm_get_profile_parametric(cmm,
 		params.gamma, params.whitepoint, params.primaries);
 }
 
@@ -1255,17 +1260,17 @@ load_jpeg_finalize(FivIoImage *image, bool cmyk,
 		g_byte_array_free(meta.icc, TRUE);
 
 	FivIoProfile *source = NULL;
-	if (icc_profile)
-		source = fiv_io_profile_new(
+	if (icc_profile && ctx->cmm)
+		source = fiv_io_cmm_get_profile(ctx->cmm,
 			g_bytes_get_data(icc_profile, NULL), g_bytes_get_size(icc_profile));
-	else if (image->exif)
-		source = parse_exif_profile(
+	else if (image->exif && ctx->cmm)
+		source = parse_exif_profile(ctx->cmm,
 			g_bytes_get_data(image->exif, NULL), g_bytes_get_size(image->exif));
 
 	if (cmyk)
-		fiv_io_profile_cmyk(image, source, ctx->screen_profile);
+		fiv_io_cmm_cmyk(ctx->cmm, image, source, ctx->screen_profile);
 	else
-		fiv_io_profile_any(image, source, ctx->screen_profile);
+		fiv_io_cmm_any(ctx->cmm, image, source, ctx->screen_profile);
 
 	if (source)
 		fiv_io_profile_free(source);
@@ -1666,7 +1671,8 @@ open_libwebp(
 
 	WebPDemuxDelete(demux);
 	if (ctx->screen_profile)
-		fiv_io_profile_argb32_premultiply_page(result, ctx->screen_profile);
+		fiv_io_cmm_argb32_premultiply_page(
+			ctx->cmm, result, ctx->screen_profile);
 
 fail:
 	WebPFreeDecBuffer(&config.output);
@@ -2048,7 +2054,7 @@ open_libraw(
 
 out:
 	libraw_close(iprc);
-	return fiv_io_profile_finalize(result, ctx->screen_profile);
+	return fiv_io_cmm_finish(ctx->cmm, result, ctx->screen_profile);
 }
 
 #endif  // HAVE_LIBRAW ---------------------------------------------------------
@@ -2070,8 +2076,8 @@ load_resvg_destroy(FivIoRenderClosure *closure)
 }
 
 static FivIoImage *
-load_resvg_render_internal(FivIoRenderClosureResvg *self,
-	double scale, FivIoProfile *target, GError **error)
+load_resvg_render_internal(FivIoRenderClosureResvg *self, double scale,
+	FivIoCmm *cmm, FivIoProfile *target, GError **error)
 {
 	double w = ceil(self->width * scale), h = ceil(self->height * scale);
 	if (w > SHRT_MAX || h > SHRT_MAX) {
@@ -2101,15 +2107,15 @@ load_resvg_render_internal(FivIoRenderClosureResvg *self,
 		uint32_t rgba = g_ntohl(pixels[i]);
 		pixels[i] = rgba << 24 | rgba >> 8;
 	}
-	return fiv_io_profile_finalize(image, target);
+	return fiv_io_cmm_finish(cmm, image, target);
 }
 
 static FivIoImage *
-load_resvg_render(
-	FivIoRenderClosure *closure, FivIoProfile *target, double scale)
+load_resvg_render(FivIoRenderClosure *closure,
+	FivIoCmm *cmm, FivIoProfile *target, double scale)
 {
 	FivIoRenderClosureResvg *self = (FivIoRenderClosureResvg *) closure;
-	return load_resvg_render_internal(self, scale, target, NULL);
+	return load_resvg_render_internal(self, scale, cmm, target, NULL);
 }
 
 static const char *
@@ -2167,8 +2173,8 @@ open_resvg(
 	closure->width = size.width;
 	closure->height = size.height;
 
-	FivIoImage *image =
-		load_resvg_render_internal(closure, 1., ctx->screen_profile, error);
+	FivIoImage *image = load_resvg_render_internal(
+		closure, 1., ctx->cmm, ctx->screen_profile, error);
 	if (!image) {
 		load_resvg_destroy(&closure->parent);
 		return NULL;
@@ -2198,7 +2204,7 @@ load_librsvg_destroy(FivIoRenderClosure *closure)
 
 static FivIoImage *
 load_librsvg_render_internal(FivIoRenderClosureLibrsvg *self, double scale,
-	FivIoProfile *target, GError **error)
+	FivIoCmm *cmm, FivIoProfile *target, GError **error)
 {
 	RsvgRectangle viewport = {.x = 0, .y = 0,
 		.width = self->width * scale, .height = self->height * scale};
@@ -2225,15 +2231,15 @@ load_librsvg_render_internal(FivIoRenderClosureLibrsvg *self, double scale,
 		fiv_io_image_unref(image);
 		return NULL;
 	}
-	return fiv_io_profile_finalize(image, target);
+	return fiv_io_cmm_finish(cmm, image, target);
 }
 
 static FivIoImage *
-load_librsvg_render(
-	FivIoRenderClosure *closure, FivIoProfile *target, double scale)
+load_librsvg_render(FivIoRenderClosure *closure,
+	FivIoCmm *cmm, FivIoProfile *target, double scale)
 {
 	FivIoRenderClosureLibrsvg *self = (FivIoRenderClosureLibrsvg *) closure;
-	return load_librsvg_render_internal(self, scale, target, NULL);
+	return load_librsvg_render_internal(self, scale, cmm, target, NULL);
 }
 
 static FivIoImage *
@@ -2282,8 +2288,8 @@ open_librsvg(
 
 	// librsvg rasterizes filters, so rendering to a recording Cairo surface
 	// has been abandoned.
-	FivIoImage *image =
-		load_librsvg_render_internal(closure, 1., ctx->screen_profile, error);
+	FivIoImage *image = load_librsvg_render_internal(
+		closure, 1., ctx->cmm, ctx->screen_profile, error);
 	if (!image) {
 		load_librsvg_destroy(&closure->parent);
 		return NULL;
@@ -2599,7 +2605,7 @@ open_libheif(
 	g_free(ids);
 fail_read:
 	heif_context_free(ctx);
-	return fiv_io_profile_finalize(result, ioctx->screen_profile);
+	return fiv_io_cmm_finish(ioctx->cmm, result, ioctx->screen_profile);
 }
 
 #endif  // HAVE_LIBHEIF --------------------------------------------------------
@@ -2830,7 +2836,7 @@ fail:
 	TIFFSetWarningHandlerExt(whe);
 	TIFFSetErrorHandler(eh);
 	TIFFSetWarningHandler(wh);
-	return fiv_io_profile_finalize(result, ctx->screen_profile);
+	return fiv_io_cmm_finish(ctx->cmm, result, ctx->screen_profile);
 }
 
 #endif  // HAVE_LIBTIFF --------------------------------------------------------
@@ -2925,9 +2931,10 @@ open_gdkpixbuf(
 
 	g_object_unref(pixbuf);
 	if (custom_argb32)
-		fiv_io_profile_argb32_premultiply_page(image, ctx->screen_profile);
+		fiv_io_cmm_argb32_premultiply_page(
+			ctx->cmm, image, ctx->screen_profile);
 	else
-		image = fiv_io_profile_finalize(image, ctx->screen_profile);
+		image = fiv_io_cmm_finish(ctx->cmm, image, ctx->screen_profile);
 	return image;
 }
 
diff --git a/fiv-io.h b/fiv-io.h
index fda9319..c8d22c4 100644
--- a/fiv-io.h
+++ b/fiv-io.h
@@ -25,41 +25,50 @@
 typedef enum _FivIoOrientation FivIoOrientation;
 typedef struct _FivIoRenderClosure FivIoRenderClosure;
 typedef struct _FivIoImage FivIoImage;
+typedef struct _FivIoProfile FivIoProfile;
 
 // --- Colour management -------------------------------------------------------
+// Note that without a CMM, all FivIoCmm and FivIoProfile will be returned NULL.
 
-void fiv_io_profile_init(void);
-
-// TODO(p): Make it also possible to use Skia's skcms.
-typedef void *FivIoProfile;
-FivIoProfile *fiv_io_profile_new(const void *data, size_t len);
-FivIoProfile *fiv_io_profile_new_from_bytes(GBytes *bytes);
-FivIoProfile *fiv_io_profile_new_sRGB(void);
-FivIoProfile *fiv_io_profile_new_sRGB_gamma(double gamma);
-FivIoProfile *fiv_io_profile_new_parametric(
-    double gamma, double whitepoint[2], double primaries[6]);
 GBytes *fiv_io_profile_to_bytes(FivIoProfile *profile);
 void fiv_io_profile_free(FivIoProfile *self);
 
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 
+#define FIV_TYPE_IO_CMM (fiv_io_cmm_get_type())
+G_DECLARE_FINAL_TYPE(FivIoCmm, fiv_io_cmm, FIV, IO_CMM, GObject)
+
+FivIoCmm *fiv_io_cmm_get_default(void);
+
+FivIoProfile *fiv_io_cmm_get_profile(
+	FivIoCmm *self, const void *data, size_t len);
+FivIoProfile *fiv_io_cmm_get_profile_from_bytes(FivIoCmm *self, GBytes *bytes);
+FivIoProfile *fiv_io_cmm_get_profile_sRGB(FivIoCmm *self);
+FivIoProfile *fiv_io_cmm_get_profile_sRGB_gamma(FivIoCmm *self, double gamma);
+FivIoProfile *fiv_io_cmm_get_profile_parametric(
+	FivIoCmm *self, double gamma, double whitepoint[2], double primaries[6]);
+
+// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+
 void fiv_io_premultiply_argb32(FivIoImage *image);
 
-void fiv_io_profile_cmyk(
+void fiv_io_cmm_cmyk(FivIoCmm *self,
     FivIoImage *image, FivIoProfile *source, FivIoProfile *target);
-void fiv_io_profile_4x16le_direct(unsigned char *data,
+void fiv_io_cmm_4x16le_direct(FivIoCmm *self, unsigned char *data,
     int w, int h, FivIoProfile *source, FivIoProfile *target);
-void fiv_io_profile_argb32_premultiply(
-    FivIoImage *image, FivIoProfile *source, FivIoProfile *target);
 
-void fiv_io_profile_page(FivIoImage *page, FivIoProfile *target,
-	void (*frame_cb) (FivIoImage *, FivIoProfile *, FivIoProfile *));
-#define fiv_io_profile_argb32_premultiply_page(page, target) \
-	fiv_io_profile_page((page), (target), fiv_io_profile_argb32_premultiply)
+void fiv_io_cmm_argb32_premultiply(FivIoCmm *self,
+	FivIoImage *image, FivIoProfile *source, FivIoProfile *target);
+#define fiv_io_cmm_argb32_premultiply_page(cmm, page, target) \
+	fiv_io_cmm_page((cmm), (page), (target), fiv_io_cmm_argb32_premultiply)
 
-void fiv_io_profile_any(
+void fiv_io_cmm_page(FivIoCmm *self, FivIoImage *page, FivIoProfile *target,
+	void (*frame_cb) (FivIoCmm *,
+		FivIoImage *, FivIoProfile *, FivIoProfile *));
+void fiv_io_cmm_any(FivIoCmm *self,
 	FivIoImage *image, FivIoProfile *source, FivIoProfile *target);
-FivIoImage *fiv_io_profile_finalize(FivIoImage *image, FivIoProfile *target);
+FivIoImage *fiv_io_cmm_finish(FivIoCmm *self,
+	FivIoImage *image, FivIoProfile *target);
 
 // --- Loading -----------------------------------------------------------------
 
@@ -84,7 +93,8 @@ enum _FivIoOrientation {
 // then loaders could store it in their closures.
 struct _FivIoRenderClosure {
 	/// The rendering is allowed to fail, returning NULL.
-	FivIoImage *(*render)(FivIoRenderClosure *, FivIoProfile *, double scale);
+	FivIoImage *(*render)(
+		FivIoRenderClosure *, FivIoCmm *, FivIoProfile *, double scale);
 	void (*destroy)(FivIoRenderClosure *);
 };
 
@@ -155,7 +165,8 @@ cairo_surface_t *fiv_io_image_to_surface_noref(const FivIoImage *image);
 
 typedef struct {
 	const char *uri;                    ///< Source URI
-	FivIoProfile screen_profile;        ///< Target colour space or NULL
+	FivIoCmm *cmm;                      ///< Colour management module or NULL
+	FivIoProfile *screen_profile;       ///< Target colour space or NULL
 	int screen_dpi;                     ///< Target DPI
 	gboolean enhance;                   ///< Enhance JPEG (currently)
 	gboolean first_frame_only;          ///< Only interested in the 1st frame
diff --git a/fiv-thumbnail.c b/fiv-thumbnail.c
index 6ff1246..80f378e 100644
--- a/fiv-thumbnail.c
+++ b/fiv-thumbnail.c
@@ -137,10 +137,12 @@ might_be_a_thumbnail(const char *path_or_uri)
 static FivIoImage *
 render(GFile *target, GBytes *data, gboolean *color_managed, GError **error)
 {
+	FivIoCmm *cmm = fiv_io_cmm_get_default();
 	FivIoOpenContext ctx = {
 		.uri = g_file_get_uri(target),
 		// Remember to synchronize changes with adjust_thumbnail().
-		.screen_profile = fiv_io_profile_new_sRGB(),
+		.cmm = cmm,
+		.screen_profile = fiv_io_cmm_get_profile_sRGB(cmm),
 		.screen_dpi = 96,
 		.first_frame_only = TRUE,
 		// Only using this array as a redirect.
@@ -182,9 +184,11 @@ adjust_thumbnail(FivIoImage *thumbnail, double row_height)
 	FivIoRenderClosure *closure = thumbnail->render;
 	if (closure && orientation <= FivIoOrientation0) {
 		// Remember to synchronize changes with render().
-		FivIoProfile *screen_profile = fiv_io_profile_new_sRGB();
+		FivIoCmm *cmm = fiv_io_cmm_get_default();
+		FivIoProfile *screen_profile = fiv_io_cmm_get_profile_sRGB(cmm);
 		// This API doesn't accept non-uniform scaling; prefer a vertical fit.
-		FivIoImage *scaled = closure->render(closure, screen_profile, scale_y);
+		FivIoImage *scaled =
+			closure->render(closure, cmm, screen_profile, scale_y);
 		if (screen_profile)
 			fiv_io_profile_free(screen_profile);
 		if (scaled)
diff --git a/fiv-view.c b/fiv-view.c
index 0025d47..fbcb769 100644
--- a/fiv-view.c
+++ b/fiv-view.c
@@ -417,6 +417,7 @@ prescale_page(FivView *self)
 	// If it fails, the previous frame pointer may become invalid.
 	g_clear_pointer(&self->page_scaled, fiv_io_image_unref);
 	self->frame = self->page_scaled = closure->render(closure,
+		self->enable_cms ? fiv_io_cmm_get_default() : NULL,
 		self->enable_cms ? self->screen_cms_profile : NULL, self->scale);
 	if (!self->page_scaled)
 		self->frame = self->page;
@@ -475,7 +476,8 @@ monitor_cms_profile(GdkWindow *root, int num)
 	if (gdk_property_get(root, gdk_atom_intern(atom, FALSE), GDK_NONE, 0,
 			8 << 20 /* MiB */, FALSE, &type, &format, &length, &data)) {
 		if (format == 8 && length > 0)
-			result = fiv_io_profile_new(data, length);
+			result = fiv_io_cmm_get_profile(
+				fiv_io_cmm_get_default(), data, length);
 		g_free(data);
 	}
 	return result;
@@ -525,7 +527,8 @@ reload_screen_cms_profile(FivView *self, GdkWindow *window)
 
 out:
 	if (!self->screen_cms_profile)
-		self->screen_cms_profile = fiv_io_profile_new_sRGB();
+		self->screen_cms_profile =
+			fiv_io_cmm_get_profile_sRGB(fiv_io_cmm_get_default());
 }
 
 static void
@@ -1381,6 +1384,7 @@ open_without_swapping_in(FivView *self, const char *uri)
 {
 	FivIoOpenContext ctx = {
 		.uri = uri,
+		.cmm = self->enable_cms ? fiv_io_cmm_get_default() : NULL,
 		.screen_profile = self->enable_cms ? self->screen_cms_profile : NULL,
 		.screen_dpi = 96,  // TODO(p): Try to retrieve it from the screen.
 		.enhance = self->enhance,
diff --git a/fiv.c b/fiv.c
index f4f612e..43041b0 100644
--- a/fiv.c
+++ b/fiv.c
@@ -2583,8 +2583,6 @@ on_app_handle_local_options(G_GNUC_UNUSED GApplication *app,
 		return 0;
 	}
 
-	fiv_io_profile_init();
-
 	// Normalize all arguments to URIs, and run thumbnailing modes first.
 	for (gsize i = 0; o.args && o.args[i]; i++) {
 		GFile *resolved = g_file_new_for_commandline_arg(o.args[i]);
diff --git a/meson.build b/meson.build
index 2d854e7..bf18196 100644
--- a/meson.build
+++ b/meson.build
@@ -164,7 +164,7 @@ tiff_tables = custom_target('tiff-tables.h',
 )
 
 desktops = ['fiv.desktop', 'fiv-browse.desktop']
-iolib = static_library('fiv-io', 'fiv-io.c', 'fiv-io-profile.c', 'xdg.c',
+iolib = static_library('fiv-io', 'fiv-io.c', 'fiv-io-cmm.c', 'xdg.c',
 	tiff_tables,
 	dependencies : dependencies).extract_all_objects(recursive : true)
 exe = executable('fiv', 'fiv.c', 'fiv-view.c', 'fiv-context-menu.c',