Move colour management to its own compilation unit

Also make it apparent that CMM profiles are pointer types.

This isn't all that pretty, but it's a necessary first step.

7 files changed, 419 insertions, 368 deletions

diff --git a/fiv-io-profile.c b/fiv-io-profile.c
new file mode 100644
index 0000000..84b310e
--- /dev/null
+++ b/fiv-io-profile.c
@@ -0,0 +1,366 @@
+//
+// fiv-profile.c: colour management
+//
+// Copyright (c) 2024, Přemysl Eric Janouch <p@janouch.name>
+//
+// Permission to use, copy, modify, and/or distribute this software for any
+// purpose with or without fee is hereby granted.
+//
+// THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+// WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+// MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
+// SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+// WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
+// OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
+// CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+//
+
+#include "config.h"
+
+#include <glib.h>
+#include <stdbool.h>
+
+#include "fiv-io.h"
+
+// Colour management must be handled before RGB conversions.
+#ifdef HAVE_LCMS2
+#include <lcms2.h>
+#endif  // HAVE_LCMS2
+#ifdef HAVE_LCMS2_FAST_FLOAT
+#include <lcms2_fast_float.h>
+#endif  // HAVE_LCMS2_FAST_FLOAT
+
+void
+fiv_io_profile_init(void)
+{
+	// TODO(p): Use Little CMS with contexts instead.
+#ifdef HAVE_LCMS2_FAST_FLOAT
+	cmsPluginTHR(NULL, cmsFastFloatExtensions());
+#endif  // HAVE_LCMS2_FAST_FLOAT
+}
+
+FivIoProfile *
+fiv_io_profile_new(const void *data, size_t len)
+{
+#ifdef HAVE_LCMS2
+	return cmsOpenProfileFromMemTHR(NULL, data, len);
+#else
+	(void) data;
+	(void) len;
+	return NULL;
+#endif
+}
+
+FivIoProfile *
+fiv_io_profile_new_sRGB(void)
+{
+#ifdef HAVE_LCMS2
+	return cmsCreate_sRGBProfileTHR(NULL);
+#else
+	return NULL;
+#endif
+}
+
+FivIoProfile *
+fiv_io_profile_new_parametric(
+	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;
+
+	const cmsCIExyY cmsWP = {whitepoint[0], whitepoint[1], 1.0};
+	const cmsCIExyYTRIPLE cmsP = {
+		{primaries[0], primaries[1], 1.0},
+		{primaries[2], primaries[3], 1.0},
+		{primaries[4], primaries[5], 1.0},
+	};
+
+	cmsToneCurve *curve = cmsBuildGamma(context, gamma);
+	if (!curve)
+		return NULL;
+
+	cmsHPROFILE profile = cmsCreateRGBProfileTHR(
+		context, &cmsWP, &cmsP, (cmsToneCurve *[3]){curve, curve, curve});
+	cmsFreeToneCurve(curve);
+	return profile;
+#else
+	(void) gamma;
+	(void) whitepoint;
+	(void) primaries;
+	return NULL;
+#endif
+}
+
+FivIoProfile *
+fiv_io_profile_new_sRGB_gamma(double gamma)
+{
+	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});
+}
+
+FivIoProfile *
+fiv_io_profile_new_from_bytes(GBytes *bytes)
+{
+	gsize len = 0;
+	gconstpointer p = g_bytes_get_data(bytes, &len);
+	return fiv_io_profile_new(p, len);
+}
+
+GBytes *
+fiv_io_profile_to_bytes(FivIoProfile *profile)
+{
+#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)
+{
+#ifdef HAVE_LCMS2
+	cmsCloseProfile(self);
+#else
+	(void) self;
+#endif
+}
+
+// --- Image loading -----------------------------------------------------------
+
+// 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(
+	FivIoImage *image, FivIoProfile *source, FivIoProfile *target)
+{
+#ifndef HAVE_LCMS2
+	(void) source;
+	(void) target;
+#else
+	cmsHTRANSFORM transform = NULL;
+	if (source && target) {
+		transform = cmsCreateTransformTHR(NULL, source, TYPE_CMYK_8_REV, target,
+			FIV_IO_PROFILE_ARGB32, INTENT_PERCEPTUAL, 0);
+	}
+	if (transform) {
+		cmsDoTransform(
+			transform, image->data, image->data, image->width * image->height);
+		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,
+	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
+	// TODO(p): We should make this optional.
+	cmsHPROFILE src_fallback = NULL;
+	if (target && !source)
+		source = src_fallback = cmsCreate_sRGBProfileTHR(NULL);
+
+	cmsHTRANSFORM transform = NULL;
+	if (source && target) {
+		transform = cmsCreateTransformTHR(NULL,
+			source, source_format, target, target_format, INTENT_PERCEPTUAL, 0);
+	}
+	if (transform) {
+		cmsDoTransform(transform, data, data, w * h);
+		cmsDeleteTransform(transform);
+	}
+	if (src_fallback)
+		cmsCloseProfile(src_fallback);
+	return transform != NULL;
+#endif
+}
+
+static void
+fiv_io_profile_xrgb32(
+	FivIoImage *image, FivIoProfile *source, FivIoProfile *target)
+{
+	fiv_io_profile_rgb_direct(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,
+	int w, int h, FivIoProfile *source, FivIoProfile *target)
+{
+	fiv_io_profile_rgb_direct(data, w, h, source, target,
+		FIV_IO_PROFILE_4X16LE, FIV_IO_PROFILE_4X16LE);
+}
+
+// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+
+void
+fiv_io_profile_page(FivIoImage *page, FivIoProfile *target,
+	void (*frame_cb) (FivIoImage *, 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);
+}
+
+// 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);
+		}
+	}
+}
+
+#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,
+	FivIoProfile *source, FivIoProfile *target)
+{
+	g_return_if_fail(image->format == CAIRO_FORMAT_ARGB32);
+
+	fiv_io_profile_rgb_direct(image->data, image->width, image->height,
+		source, target,
+		FIV_IO_PROFILE_ARGB32_PREMUL, FIV_IO_PROFILE_ARGB32_PREMUL);
+}
+
+void
+fiv_io_profile_argb32_premultiply(
+	FivIoImage *image, FivIoProfile *source, FivIoProfile *target)
+{
+	if (image->format != CAIRO_FORMAT_ARGB32) {
+		fiv_io_profile_xrgb32(image, source, target);
+	} else if (!fiv_io_profile_rgb_direct(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");
+		fiv_io_premultiply_argb32(image);
+	}
+}
+
+#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(
+	FivIoImage *image, FivIoProfile *source, FivIoProfile *target)
+{
+	fiv_io_profile_xrgb32(image, source, target);
+	fiv_io_premultiply_argb32(image);
+}
+
+#endif  // ! HAVE_LCMS2 || LCMS_VERSION < 2130
+
+// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+
+void
+fiv_io_profile_any(
+	FivIoImage *image, FivIoProfile *source, FivIoProfile *target)
+{
+	// TODO(p): Ensure we do colour management early enough, so that
+	// no avoidable increase of quantization error occurs beforehands,
+	// and also for correct alpha compositing.
+	switch (image->format) {
+	break; case CAIRO_FORMAT_RGB24:
+		fiv_io_profile_xrgb32(image, source, target);
+	break; case CAIRO_FORMAT_ARGB32:
+		fiv_io_profile_argb32(image, source, target);
+	break; default:
+		g_debug("CM attempted on an unsupported surface format");
+	}
+}
+
+// TODO(p): Offer better integration, upgrade the bit depth if appropriate.
+FivIoImage *
+fiv_io_profile_finalize(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);
+	return image;
+}
diff --git a/fiv-io.c b/fiv-io.c
index 2ed5d39..ce30f2d 100644
--- a/fiv-io.c
+++ b/fiv-io.c
@@ -34,11 +34,6 @@
 #include <libjpegqs.h>
 #endif  // HAVE_JPEG_QS
 
-// Colour management must be handled before RGB conversions.
-#ifdef HAVE_LCMS2
-#include <lcms2.h>
-#endif  // HAVE_LCMS2
-
 #define TIFF_TABLES_CONSTANTS_ONLY
 #include "tiff-tables.h"
 #include "tiffer.h"
@@ -291,333 +286,6 @@ try_append_page(
 	return true;
 }
 
-// --- Colour management -------------------------------------------------------
-
-FivIoProfile
-fiv_io_profile_new(const void *data, size_t len)
-{
-#ifdef HAVE_LCMS2
-	return cmsOpenProfileFromMemTHR(NULL, data, len);
-#else
-	(void) data;
-	(void) len;
-	return NULL;
-#endif
-}
-
-FivIoProfile
-fiv_io_profile_new_sRGB(void)
-{
-#ifdef HAVE_LCMS2
-	return cmsCreate_sRGBProfileTHR(NULL);
-#else
-	return NULL;
-#endif
-}
-
-FivIoProfile
-fiv_io_profile_new_parametric(
-	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;
-
-	const cmsCIExyY cmsWP = {whitepoint[0], whitepoint[1], 1.0};
-	const cmsCIExyYTRIPLE cmsP = {
-		{primaries[0], primaries[1], 1.0},
-		{primaries[2], primaries[3], 1.0},
-		{primaries[4], primaries[5], 1.0},
-	};
-
-	cmsToneCurve *curve = cmsBuildGamma(context, gamma);
-	if (!curve)
-		return NULL;
-
-	cmsHPROFILE profile = cmsCreateRGBProfileTHR(
-		context, &cmsWP, &cmsP, (cmsToneCurve *[3]){curve, curve, curve});
-	cmsFreeToneCurve(curve);
-	return profile;
-#else
-	(void) gamma;
-	(void) whitepoint;
-	(void) primaries;
-	return NULL;
-#endif
-}
-
-FivIoProfile
-fiv_io_profile_new_sRGB_gamma(double gamma)
-{
-	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});
-}
-
-static FivIoProfile
-fiv_io_profile_new_from_bytes(GBytes *bytes)
-{
-	gsize len = 0;
-	gconstpointer p = g_bytes_get_data(bytes, &len);
-	return fiv_io_profile_new(p, len);
-}
-
-static GBytes *
-fiv_io_profile_to_bytes(FivIoProfile profile)
-{
-#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)
-{
-#ifdef HAVE_LCMS2
-	cmsCloseProfile(self);
-#else
-	(void) self;
-#endif
-}
-
-// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
-
-// 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;
-	}
-}
-
-static void
-fiv_io_profile_cmyk(
-	FivIoImage *image, FivIoProfile source, FivIoProfile target)
-{
-#ifndef HAVE_LCMS2
-	(void) source;
-	(void) target;
-#else
-	cmsHTRANSFORM transform = NULL;
-	if (source && target) {
-		transform = cmsCreateTransformTHR(NULL, source, TYPE_CMYK_8_REV, target,
-			FIV_IO_PROFILE_ARGB32, INTENT_PERCEPTUAL, 0);
-	}
-	if (transform) {
-		cmsDoTransform(
-			transform, image->data, image->data, image->width * image->height);
-		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,
-	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
-	// TODO(p): We should make this optional.
-	cmsHPROFILE src_fallback = NULL;
-	if (target && !source)
-		source = src_fallback = cmsCreate_sRGBProfileTHR(NULL);
-
-	cmsHTRANSFORM transform = NULL;
-	if (source && target) {
-		transform = cmsCreateTransformTHR(NULL,
-			source, source_format, target, target_format, INTENT_PERCEPTUAL, 0);
-	}
-	if (transform) {
-		cmsDoTransform(transform, data, data, w * h);
-		cmsDeleteTransform(transform);
-	}
-	if (src_fallback)
-		cmsCloseProfile(src_fallback);
-	return transform != NULL;
-#endif
-}
-
-static void
-fiv_io_profile_xrgb32(
-	FivIoImage *image, FivIoProfile source, FivIoProfile target)
-{
-	fiv_io_profile_rgb_direct(image->data, image->width, image->height,
-		source, target, FIV_IO_PROFILE_ARGB32, FIV_IO_PROFILE_ARGB32);
-}
-
-static void
-fiv_io_profile_4x16le_direct(
-	unsigned char *data, int w, int h, FivIoProfile source, FivIoProfile target)
-{
-	fiv_io_profile_rgb_direct(data, w, h, source, target,
-		FIV_IO_PROFILE_4X16LE, FIV_IO_PROFILE_4X16LE);
-}
-
-// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
-
-static void
-fiv_io_profile_page(FivIoImage *page, FivIoProfile target,
-	void (*frame_cb) (FivIoImage *, 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);
-}
-
-static 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);
-		}
-	}
-}
-
-#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,
-	FivIoProfile source, FivIoProfile target)
-{
-	g_return_if_fail(image->format == CAIRO_FORMAT_ARGB32);
-
-	fiv_io_profile_rgb_direct(image->data, image->width, image->height,
-		source, target,
-		FIV_IO_PROFILE_ARGB32_PREMUL, FIV_IO_PROFILE_ARGB32_PREMUL);
-}
-
-static void
-fiv_io_profile_argb32_premultiply(
-	FivIoImage *image, FivIoProfile source, FivIoProfile target)
-{
-	if (image->format != CAIRO_FORMAT_ARGB32) {
-		fiv_io_profile_xrgb32(image, source, target);
-	} else if (!fiv_io_profile_rgb_direct(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");
-		fiv_io_premultiply_argb32(image);
-	}
-}
-
-#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(
-	FivIoImage *image, FivIoProfile source, FivIoProfile target)
-{
-	fiv_io_profile_xrgb32(image, source, target);
-	fiv_io_premultiply_argb32(image);
-}
-
-#endif  // ! HAVE_LCMS2 || LCMS_VERSION < 2130
-
-#define fiv_io_profile_argb32_premultiply_page(page, target) \
-	fiv_io_profile_page((page), (target), fiv_io_profile_argb32_premultiply)
-
-// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
-
-static void
-fiv_io_profile_any(FivIoImage *image, FivIoProfile source, FivIoProfile target)
-{
-	// TODO(p): Ensure we do colour management early enough, so that
-	// no avoidable increase of quantization error occurs beforehands,
-	// and also for correct alpha compositing.
-	switch (image->format) {
-	break; case CAIRO_FORMAT_RGB24:
-		fiv_io_profile_xrgb32(image, source, target);
-	break; case CAIRO_FORMAT_ARGB32:
-		fiv_io_profile_argb32(image, source, target);
-	break; default:
-		g_debug("CM attempted on an unsupported surface format");
-	}
-}
-
-// TODO(p): Offer better integration, upgrade the bit depth if appropriate.
-static FivIoImage *
-fiv_io_profile_finalize(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);
-	return image;
-}
-
 // --- Wuffs -------------------------------------------------------------------
 
 static bool
@@ -711,8 +379,8 @@ struct load_wuffs_frame_context {
 	GBytes *meta_iccp;                  ///< Reference-counted ICC profile
 	GBytes *meta_xmp;                   ///< Reference-counted XMP
 
-	FivIoProfile target;                ///< Target device profile, if any
-	FivIoProfile source;                ///< Source colour profile, if any
+	FivIoProfile *target;               ///< Target device profile, if any
+	FivIoProfile *source;               ///< Source colour profile, if any
 
 	FivIoImage *result;                 ///< The resulting image (referenced)
 	FivIoImage *result_tail;            ///< The final animation frame
@@ -1390,7 +1058,7 @@ parse_exif_profile_subifd(
 	}
 }
 
-static FivIoProfile
+static FivIoProfile *
 parse_exif_profile(const void *data, size_t len)
 {
 	struct tiffer T = {};
@@ -1586,7 +1254,7 @@ load_jpeg_finalize(FivIoImage *image, bool cmyk,
 	else
 		g_byte_array_free(meta.icc, TRUE);
 
-	FivIoProfile source = NULL;
+	FivIoProfile *source = NULL;
 	if (icc_profile)
 		source = fiv_io_profile_new(
 			g_bytes_get_data(icc_profile, NULL), g_bytes_get_size(icc_profile));
@@ -2403,7 +2071,7 @@ load_resvg_destroy(FivIoRenderClosure *closure)
 
 static FivIoImage *
 load_resvg_render_internal(FivIoRenderClosureResvg *self,
-	double scale, FivIoProfile target, GError **error)
+	double scale, FivIoProfile *target, GError **error)
 {
 	double w = ceil(self->width * scale), h = ceil(self->height * scale);
 	if (w > SHRT_MAX || h > SHRT_MAX) {
@@ -2438,7 +2106,7 @@ load_resvg_render_internal(FivIoRenderClosureResvg *self,
 
 static FivIoImage *
 load_resvg_render(
-	FivIoRenderClosure *closure, FivIoProfile target, double scale)
+	FivIoRenderClosure *closure, FivIoProfile *target, double scale)
 {
 	FivIoRenderClosureResvg *self = (FivIoRenderClosureResvg *) closure;
 	return load_resvg_render_internal(self, scale, target, NULL);
@@ -2530,7 +2198,7 @@ load_librsvg_destroy(FivIoRenderClosure *closure)
 
 static FivIoImage *
 load_librsvg_render_internal(FivIoRenderClosureLibrsvg *self, double scale,
-	FivIoProfile target, GError **error)
+	FivIoProfile *target, GError **error)
 {
 	RsvgRectangle viewport = {.x = 0, .y = 0,
 		.width = self->width * scale, .height = self->height * scale};
@@ -2562,7 +2230,7 @@ load_librsvg_render_internal(FivIoRenderClosureLibrsvg *self, double scale,
 
 static FivIoImage *
 load_librsvg_render(
-	FivIoRenderClosure *closure, FivIoProfile target, double scale)
+	FivIoRenderClosure *closure, FivIoProfile *target, double scale)
 {
 	FivIoRenderClosureLibrsvg *self = (FivIoRenderClosureLibrsvg *) closure;
 	return load_librsvg_render_internal(self, scale, target, NULL);
@@ -3712,7 +3380,7 @@ set_metadata(WebPMux *mux, const char *fourcc, GBytes *data)
 }
 
 gboolean
-fiv_io_save(FivIoImage *page, FivIoImage *frame, FivIoProfile target,
+fiv_io_save(FivIoImage *page, FivIoImage *frame, FivIoProfile *target,
 	const char *path, GError **error)
 {
 	g_return_val_if_fail(page != NULL, FALSE);
diff --git a/fiv-io.h b/fiv-io.h
index ea9c6c4..fda9319 100644
--- a/fiv-io.h
+++ b/fiv-io.h
@@ -1,7 +1,7 @@
 //
 // fiv-io.h: image operations
 //
-// Copyright (c) 2021 - 2023, Přemysl Eric Janouch <p@janouch.name>
+// Copyright (c) 2021 - 2024, Přemysl Eric Janouch <p@janouch.name>
 //
 // Permission to use, copy, modify, and/or distribute this software for any
 // purpose with or without fee is hereby granted.
@@ -22,16 +22,44 @@
 #include <glib.h>
 #include <webp/encode.h>  // WebPConfig
 
+typedef enum _FivIoOrientation FivIoOrientation;
+typedef struct _FivIoRenderClosure FivIoRenderClosure;
+typedef struct _FivIoImage FivIoImage;
+
 // --- Colour management -------------------------------------------------------
 
+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_sRGB(void);
-void fiv_io_profile_free(FivIoProfile self);
+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);
+
+// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 
-// 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);
+
+void fiv_io_profile_cmyk(
+    FivIoImage *image, FivIoProfile *source, FivIoProfile *target);
+void fiv_io_profile_4x16le_direct(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_profile_any(
+	FivIoImage *image, FivIoProfile *source, FivIoProfile *target);
+FivIoImage *fiv_io_profile_finalize(FivIoImage *image, FivIoProfile *target);
 
 // --- Loading -----------------------------------------------------------------
 
@@ -39,10 +67,6 @@ extern const char *fiv_io_supported_media_types[];
 
 gchar **fiv_io_all_supported_media_types(void);
 
-typedef enum _FivIoOrientation FivIoOrientation;
-typedef struct _FivIoRenderClosure FivIoRenderClosure;
-typedef struct _FivIoImage FivIoImage;
-
 // https://www.cipa.jp/std/documents/e/DC-008-2012_E.pdf Table 6
 enum _FivIoOrientation {
 	FivIoOrientationUnknown   = 0,
@@ -60,7 +84,7 @@ 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 *, FivIoProfile *, double scale);
 	void (*destroy)(FivIoRenderClosure *);
 };
 
@@ -179,4 +203,4 @@ unsigned char *fiv_io_encode_webp(
 /// Saves the page as a lossless WebP still picture or animation.
 /// If no exact frame is specified, this potentially creates an animation.
 gboolean fiv_io_save(FivIoImage *page, FivIoImage *frame,
-	FivIoProfile target, const char *path, GError **error);
+	FivIoProfile *target, const char *path, GError **error);
diff --git a/fiv-thumbnail.c b/fiv-thumbnail.c
index cc0858c..6ff1246 100644
--- a/fiv-thumbnail.c
+++ b/fiv-thumbnail.c
@@ -182,7 +182,7 @@ 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();
+		FivIoProfile *screen_profile = fiv_io_profile_new_sRGB();
 		// This API doesn't accept non-uniform scaling; prefer a vertical fit.
 		FivIoImage *scaled = closure->render(closure, screen_profile, scale_y);
 		if (screen_profile)
diff --git a/fiv-view.c b/fiv-view.c
index d3e634a..0025d47 100644
--- a/fiv-view.c
+++ b/fiv-view.c
@@ -78,7 +78,7 @@ struct _FivView {
 	double drag_start[2];               ///< Adjustment values for drag origin
 
 	FivIoImage *enhance_swap;           ///< Quick swap in/out
-	FivIoProfile screen_cms_profile;    ///< Target colour profile for widget
+	FivIoProfile *screen_cms_profile;   ///< Target colour profile for widget
 
 	int remaining_loops;                ///< Greater than zero if limited
 	gint64 frame_time;                  ///< Current frame's start, µs precision
@@ -461,7 +461,7 @@ out:
 //
 // Note that Wayland does not have any appropriate protocol, as of writing:
 // https://gitlab.freedesktop.org/wayland/wayland-protocols/-/merge_requests/14
-static FivIoProfile
+static FivIoProfile *
 monitor_cms_profile(GdkWindow *root, int num)
 {
 	char atom[32] = "";
@@ -471,7 +471,7 @@ monitor_cms_profile(GdkWindow *root, int num)
 	int format = 0, length = 0;
 	GdkAtom type = GDK_NONE;
 	guchar *data = NULL;
-	FivIoProfile result = NULL;
+	FivIoProfile *result = NULL;
 	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)
@@ -1117,7 +1117,7 @@ static gboolean
 save_as(FivView *self, FivIoImage *frame)
 {
 	GtkWindow *window = get_toplevel(GTK_WIDGET(self));
-	FivIoProfile target = NULL;
+	FivIoProfile *target = NULL;
 	if (self->enable_cms && (target = self->screen_cms_profile)) {
 		GtkWidget *dialog = gtk_message_dialog_new(window, GTK_DIALOG_MODAL,
 			GTK_MESSAGE_WARNING, GTK_BUTTONS_CLOSE, "%s",
diff --git a/fiv.c b/fiv.c
index ad73537..7dcf00e 100644
--- a/fiv.c
+++ b/fiv.c
@@ -44,11 +44,6 @@
 #include "fiv-thumbnail.h"
 #include "fiv-view.h"
 
-#ifdef HAVE_LCMS2_FAST_FLOAT
-#include <lcms2.h>
-#include <lcms2_fast_float.h>
-#endif  // HAVE_LCMS2_FAST_FLOAT
-
 // --- Utilities ---------------------------------------------------------------
 
 static void exit_fatal(const char *format, ...) G_GNUC_PRINTF(1, 2);
@@ -2584,10 +2579,7 @@ on_app_handle_local_options(G_GNUC_UNUSED GApplication *app,
 		return 0;
 	}
 
-	// TODO(p): Use Little CMS with contexts instead.
-#ifdef HAVE_LCMS2_FAST_FLOAT
-	cmsPlugin(cmsFastFloatExtensions());
-#endif  // HAVE_LCMS2_FAST_FLOAT
+	fiv_io_profile_init();
 
 	// Normalize all arguments to URIs, and run thumbnailing modes first.
 	for (gsize i = 0; o.args && o.args[i]; i++) {
diff --git a/meson.build b/meson.build
index 9c616ad..2d854e7 100644
--- a/meson.build
+++ b/meson.build
@@ -164,7 +164,8 @@ tiff_tables = custom_target('tiff-tables.h',
 )
 
 desktops = ['fiv.desktop', 'fiv-browse.desktop']
-iolib = static_library('fiv-io', 'fiv-io.c', 'xdg.c', tiff_tables,
+iolib = static_library('fiv-io', 'fiv-io.c', 'fiv-io-profile.c', 'xdg.c',
+	tiff_tables,
 	dependencies : dependencies).extract_all_objects(recursive : true)
 exe = executable('fiv', 'fiv.c', 'fiv-view.c', 'fiv-context-menu.c',
 	'fiv-browser.c', 'fiv-sidebar.c', 'fiv-thumbnail.c', 'fiv-collection.c',