/* make a thumbnail ... wraps up the process of thumbnailing, including
 * premultiply, colour management etc etc
 *
 * 2/11/16
 * 	- from vipsthumbnail.c
 * 6/1/17
 * 	- add @size parameter
 * 4/5/17
 * 	- add FORCE
 * 29/5/17
 * 	- don't cache (thanks tomasc)
 * 30/8/17
 * 	- add intent option, thanks kleisauke
 * 31/10/18
 * 	- deprecate auto_rotate, add no_rotate
 * 	- implement shrink-on-load for openslide images
 * 16/11/18
 * 	- implement shrink-on-load for tiff pyramid
 * 3/2/19 kleisauke
 * 	- add option_string param to thumbnail_buffer
 * 23/4/19
 * 	- don't force import CMYK, since colourspace knows about it now
 * 24/4/19
 * 	- support multi-page (animated) images
 * 27/8/19 kleisauke
 *	- prevent over-pre-shrink in thumbnail
 * 30/9/19
 * 	- smarter heif thumbnail selection
 * 12/10/19
 * 	- add thumbnail_source
 * 2/6/20
 * 	- add subifd pyr support
 * 27/2/21
 * 	- simplify rules re. processing space, colour management and linear
 * 	  mode
 * 14/4/22
 * 	- add a seq to thumbnail_image to stop cache thrashing
 * 28/4/22
 * 	- add fail_on
 * 1/3/23 kleisauke
 *	- skip colourspace conversion when needed
 */

/*

	Copyright (C) 1991-2005 The National Gallery

	This library is free software; you can redistribute it and/or
	modify it under the terms of the GNU Lesser General Public
	License as published by the Free Software Foundation; either
	version 2.1 of the License, or (at your option) any later version.

	This library is distributed in the hope that it will be useful,
	but WITHOUT ANY WARRANTY; without even the implied warranty of
	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
	Lesser General Public License for more details.

	You should have received a copy of the GNU Lesser General Public
	License along with this library; if not, write to the Free Software
	Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
	02110-1301  USA

 */

/*

	These files are distributed with VIPS - http://www.vips.ecs.soton.ac.uk

 */

/*
#define DEBUG
 */

#ifdef HAVE_CONFIG_H
#include <config.h>
#endif /*HAVE_CONFIG_H*/
#include <glib/gi18n-lib.h>

#include <stdio.h>
#include <stdlib.h>
#include <math.h>

#include <vips/vips.h>
#include <vips/internal.h>

#define VIPS_TYPE_THUMBNAIL (vips_thumbnail_get_type())
#define VIPS_THUMBNAIL(obj) \
	(G_TYPE_CHECK_INSTANCE_CAST((obj), VIPS_TYPE_THUMBNAIL, VipsThumbnail))
#define VIPS_THUMBNAIL_CLASS(klass) \
	(G_TYPE_CHECK_CLASS_CAST((klass), \
		VIPS_TYPE_THUMBNAIL, VipsThumbnailClass))
#define VIPS_IS_THUMBNAIL(obj) \
	(G_TYPE_CHECK_INSTANCE_TYPE((obj), VIPS_TYPE_THUMBNAIL))
#define VIPS_IS_THUMBNAIL_CLASS(klass) \
	(G_TYPE_CHECK_CLASS_TYPE((klass), VIPS_TYPE_THUMBNAIL))
#define VIPS_THUMBNAIL_GET_CLASS(obj) \
	(G_TYPE_INSTANCE_GET_CLASS((obj), \
		VIPS_TYPE_THUMBNAIL, VipsThumbnailClass))

/* Should be plenty.
 */
#define MAX_LEVELS (256)

typedef struct _VipsThumbnail {
	VipsOperation parent_instance;

	VipsImage *out;
	int width;
	int height;
	VipsSize size;

	gboolean auto_rotate;
	gboolean no_rotate;
	VipsInteresting crop;
	gboolean linear;
	char *export_profile;
	char *import_profile;
	VipsIntent intent;
	VipsFailOn fail_on;

	/* Bits of info we read from the input image when we get the header of
	 * the original.
	 */
	const char *loader; /* Eg. "VipsForeignLoadJpeg*" */
	int input_width;
	int input_height;
	int page_height;
	int orientation;	/* From vips_image_get_orientation() */
	gboolean swap;		/* If we must swap width / height */
	int n_pages;		/* Pages in file */
	int n_loaded_pages; /* Pages we've loaded from file */
	int n_subifds;		/* Number of subifds */

	/* For pyramidal formats, we need to read out the size of each level.
	 */
	int level_count;
	int level_width[MAX_LEVELS];
	int level_height[MAX_LEVELS];

	/* For HEIF, try to fetch the size of the stored thumbnail.
	 */
	int heif_thumbnail_width;
	int heif_thumbnail_height;

	/* Pyramids are stored in subifds.
	 */
	gboolean subifd_pyramid;

	/* Pyramids are stored in pages.
	 */
	gboolean page_pyramid;

} VipsThumbnail;

typedef struct _VipsThumbnailClass {
	VipsOperationClass parent_class;

	/* Fill out the info section of VipsThumbnail from the input object.
	 */
	int (*get_info)(VipsThumbnail *thumbnail);

	/* Open with some kind of shrink or scale factor. Exactly what we pass
	 * and to what param depends on the loader. It'll be an integer shrink
	 * factor for vips_jpegload(), a double scale factor for vips_svgload().
	 *
	 * See VipsThumbnail::loader
	 */
	VipsImage *(*open)(VipsThumbnail *thumbnail, double factor);

} VipsThumbnailClass;

G_DEFINE_ABSTRACT_TYPE(VipsThumbnail, vips_thumbnail, VIPS_TYPE_OPERATION);

static void
vips_thumbnail_dispose(GObject *gobject)
{
#ifdef DEBUG
	printf("vips_thumbnail_dispose: ");
	vips_object_print_name(VIPS_OBJECT(gobject));
	printf("\n");
#endif /*DEBUG*/

	G_OBJECT_CLASS(vips_thumbnail_parent_class)->dispose(gobject);
}

static void
vips_thumbnail_finalize(GObject *gobject)
{
#ifdef DEBUG
	printf("vips_thumbnail_finalize: ");
	vips_object_print_name(VIPS_OBJECT(gobject));
	printf("\n");
#endif /*DEBUG*/

	G_OBJECT_CLASS(vips_thumbnail_parent_class)->finalize(gobject);
}

/* Fetch an int openslide field from metadata. These are all represented as
 * strings. Return the default value if there's any problem.
 */
static int
get_int(VipsImage *image, const char *field, int default_value)
{
	const char *str;

	if (vips_image_get_typeof(image, field) &&
		!vips_image_get_string(image, field, &str))
		return atoi(str);

	return default_value;
}

static void
vips_thumbnail_read_header(VipsThumbnail *thumbnail, VipsImage *image)
{
	thumbnail->input_width = image->Xsize;
	thumbnail->input_height = image->Ysize;
	thumbnail->orientation = vips_image_get_orientation(image);
	thumbnail->swap = vips_image_get_orientation_swap(image);
	thumbnail->page_height = vips_image_get_page_height(image);
	thumbnail->n_pages = vips_image_get_n_pages(image);
	thumbnail->n_subifds = vips_image_get_n_subifds(image);

	/* VIPS_META_N_PAGES is the number of pages in the document,
	 * not the number we've read out into this image. We calculate
	 * ourselves from page_height.
	 *
	 * vips_image_get_page_height() has verified that Ysize is a simple
	 * multiple of page_height.
	 */
	thumbnail->n_loaded_pages =
		thumbnail->input_height / thumbnail->page_height;

	/* For openslide, read out the level structure too.
	 */
	if (vips_isprefix("VipsForeignLoadOpenslide", thumbnail->loader)) {
		int level_count;
		int level;

		level_count = get_int(image, "openslide.level-count", 1);
		level_count = VIPS_CLIP(1, level_count, MAX_LEVELS);
		thumbnail->level_count = level_count;

		for (level = 0; level < level_count; level++) {
			char name[256];

			vips_snprintf(name, 256,
				"openslide.level[%d].width", level);
			thumbnail->level_width[level] =
				get_int(image, name, 0);
			vips_snprintf(name, 256,
				"openslide.level[%d].height", level);
			thumbnail->level_height[level] =
				get_int(image, name, 0);
		}
	}
}

/* Detect a pyramid made of pages following a roughly /2 shrink.
 *
 * This may not be a pyr tiff, so no error if we can't find the layers.
 */
static void
vips_thumbnail_get_pyramid_page(VipsThumbnail *thumbnail)
{
	VipsThumbnailClass *class = VIPS_THUMBNAIL_GET_CLASS(thumbnail);
	int i;

#ifdef DEBUG
	printf("vips_thumbnail_get_pyramid_page:\n");
#endif /*DEBUG*/

	/* Single-page docs can't be pyramids.
	 */
	if (thumbnail->n_pages < 2)
		return;

	for (i = 0; i < thumbnail->n_pages; i++) {
		VipsImage *page;
		int level_width;
		int level_height;
		int expected_level_width;
		int expected_level_height;

		if (!(page = class->open(thumbnail, i)))
			return;
		level_width = page->Xsize;
		level_height = page->Ysize;
		VIPS_UNREF(page);

		expected_level_width = thumbnail->input_width / (1 << i);
		expected_level_height = thumbnail->input_height / (1 << i);

		/* This won't be exact due to rounding etc.
		 */
		if (abs(level_width - expected_level_width) > 5 ||
			level_width < 2)
			return;
		if (abs(level_height - expected_level_height) > 5 ||
			level_height < 2)
			return;

		thumbnail->level_width[i] = level_width;
		thumbnail->level_height[i] = level_height;
	}

	/* Now set level_count. This signals that we've found a pyramid.
	 */
#ifdef DEBUG
	printf("vips_thumbnail_get_pyramid_page: %d layer pyramid detected\n",
		thumbnail->n_pages);
#endif /*DEBUG*/
	thumbnail->level_count = thumbnail->n_pages;
}

/* Detect a TIFF pyramid made of subifds following a roughly /2 shrink.
 *
 * This may not be a pyr tiff, so no error if we can't find the layers.
 */
static void
vips_thumbnail_get_tiff_pyramid_subifd(VipsThumbnail *thumbnail)
{
	VipsThumbnailClass *class = VIPS_THUMBNAIL_GET_CLASS(thumbnail);
	int i;

#ifdef DEBUG
	printf("vips_thumbnail_get_tiff_pyramid_subifd:\n");
#endif /*DEBUG*/

	for (i = 0; i < thumbnail->n_subifds; i++) {
		VipsImage *page;
		int level_width;
		int level_height;
		int expected_level_width;
		int expected_level_height;

		if (!(page = class->open(thumbnail, i)))
			return;
		level_width = page->Xsize;
		level_height = page->Ysize;
		VIPS_UNREF(page);

		/* The main image is size 1, subifd 0 is half that.
		 */
		expected_level_width = thumbnail->input_width / (2 << i);
		expected_level_height = thumbnail->input_height / (2 << i);

		/* This won't be exact due to rounding etc.
		 */
		if (abs(level_width - expected_level_width) > 5 ||
			level_width < 2)
			return;
		if (abs(level_height - expected_level_height) > 5 ||
			level_height < 2)
			return;

		thumbnail->level_width[i] = level_width;
		thumbnail->level_height[i] = level_height;
	}

	/* Now set level_count. This signals that we've found a pyramid.
	 */
#ifdef DEBUG
	printf("vips_thumbnail_get_tiff_pyramid_subifd: "
		   "%d layer pyramid detected\n",
		thumbnail->n_subifds);
#endif /*DEBUG*/
	thumbnail->level_count = thumbnail->n_subifds;
}

static int
vips_thumbnail_get_heif_thumb_info(VipsThumbnail *thumbnail)
{
	VipsThumbnailClass *class = VIPS_THUMBNAIL_GET_CLASS(thumbnail);

	VipsImage *thumb;

	if (!(thumb = class->open(thumbnail, 1)))
		return -1;

	if (thumb->Xsize < thumbnail->input_width) {
		thumbnail->heif_thumbnail_width = thumb->Xsize;
		thumbnail->heif_thumbnail_height = thumb->Ysize;
	}

	VIPS_UNREF(thumb);

	return 0;
}

/* Calculate the shrink factor, taking into account auto-rotate, the fit mode,
 * and so on.
 *
 * The hshrink/vshrink are the amount to shrink the input image axes by in
 * order for the output axes (ie. after rotation) to match the required
 * thumbnail->width, thumbnail->height and fit mode.
 */
static void
vips_thumbnail_calculate_shrink(VipsThumbnail *thumbnail,
	int input_width, int input_height, double *hshrink, double *vshrink)
{
	/* If we will be rotating, swap the target width and height.
	 */
	gboolean rotate =
		thumbnail->swap &&
		thumbnail->auto_rotate;
	int target_width = rotate
		? thumbnail->height
		: thumbnail->width;
	int target_height = rotate
		? thumbnail->width
		: thumbnail->height;

	VipsDirection direction;

	/* Calculate the horizontal and vertical shrink we'd need to fit the
	 * image to the bounding box, and pick the biggest.
	 *
	 * In crop mode, we aim to fill the bounding box, so we must use the
	 * smaller axis.
	 */
	*hshrink = (double) input_width / target_width;
	*vshrink = (double) input_height / target_height;

	if (thumbnail->crop != VIPS_INTERESTING_NONE) {
		if (*hshrink < *vshrink)
			direction = VIPS_DIRECTION_HORIZONTAL;
		else
			direction = VIPS_DIRECTION_VERTICAL;
	}
	else {
		if (*hshrink < *vshrink)
			direction = VIPS_DIRECTION_VERTICAL;
		else
			direction = VIPS_DIRECTION_HORIZONTAL;
	}

	if (thumbnail->size != VIPS_SIZE_FORCE) {
		if (direction == VIPS_DIRECTION_HORIZONTAL)
			*vshrink = *hshrink;
		else
			*hshrink = *vshrink;
	}

	if (thumbnail->size == VIPS_SIZE_UP) {
		*hshrink = VIPS_MIN(1, *hshrink);
		*vshrink = VIPS_MIN(1, *vshrink);
	}
	else if (thumbnail->size == VIPS_SIZE_DOWN) {
		*hshrink = VIPS_MAX(1, *hshrink);
		*vshrink = VIPS_MAX(1, *vshrink);
	}

	/* We don't want to shrink so much that we send an axis to 0.
	 */
	*hshrink = VIPS_MIN(*hshrink, input_width);
	*vshrink = VIPS_MIN(*vshrink, input_height);
}

/* Just the common part of the shrink: the bit by which both axes must be
 * shrunk.
 */
static double
vips_thumbnail_calculate_common_shrink(VipsThumbnail *thumbnail,
	int width, int height)
{
	double hshrink;
	double vshrink;
	double shrink;

	vips_thumbnail_calculate_shrink(thumbnail, width, height,
		&hshrink, &vshrink);

	shrink = VIPS_MIN(hshrink, vshrink);

	return shrink;
}

/* Find the best jpeg preload shrink.
 */
static int
vips_thumbnail_find_jpegshrink(VipsThumbnail *thumbnail,
	int width, int height)
{
	double shrink = vips_thumbnail_calculate_common_shrink(thumbnail,
		width, height);

	/* We can't use pre-shrunk images in linear mode. libjpeg shrinks in Y
	 * (of YCbCR), not linear space.
	 */
	if (thumbnail->linear)
		return 1;

	/* Shrink-on-load is a simple block shrink and will add quite a bit of
	 * extra sharpness to the image. We want to block shrink to a
	 * bit above our target, then vips_shrink() / vips_reduce() to the
	 * final size.
	 *
	 * Leave at least a factor of two for the final resize step.
	 */
	if (shrink >= 16)
		return 8;
	else if (shrink >= 8)
		return 4;
	else if (shrink >= 4)
		return 2;
	else
		return 1;
}

/* Find the best pyramid (openslide, tiff, etc.) level.
 */
static int
vips_thumbnail_find_pyrlevel(VipsThumbnail *thumbnail,
	int width, int height)
{
	int level;

	g_assert(thumbnail->level_count > 0);
	g_assert(thumbnail->level_count <= MAX_LEVELS);

	for (level = thumbnail->level_count - 1; level >= 0; level--)
		if (vips_thumbnail_calculate_common_shrink(thumbnail,
				thumbnail->level_width[level],
				thumbnail->level_height[level]) >= 1.0)
			return level;

	return 0;
}

/* Open the image, returning the best version for thumbnailing.
 *
 * For example, libjpeg supports fast shrink-on-read, so if we have a JPEG,
 * we can ask VIPS to load a lower resolution version.
 */
static VipsImage *
vips_thumbnail_open(VipsThumbnail *thumbnail)
{
	VipsThumbnailClass *class = VIPS_THUMBNAIL_GET_CLASS(thumbnail);

	VipsImage *im;
	double factor;

	if (class->get_info(thumbnail))
		return NULL;
	g_info("selected loader is %s", thumbnail->loader);
	g_info("input size is %d x %d",
		thumbnail->input_width, thumbnail->input_height);

	/* For tiff, scan the image and try to spot page-based and ifd-based
	 * pyramids.
	 */
	if (vips_isprefix("VipsForeignLoadTiff", thumbnail->loader)) {
		/* Test for a subifd pyr first, since we can do that from just
		 * one page.
		 */
		thumbnail->subifd_pyramid = TRUE;
		vips_thumbnail_get_tiff_pyramid_subifd(thumbnail);

		if (thumbnail->level_count == 0) {
			thumbnail->subifd_pyramid = FALSE;
			thumbnail->page_pyramid = TRUE;

			vips_thumbnail_get_pyramid_page(thumbnail);

			if (thumbnail->level_count == 0)
				thumbnail->page_pyramid = FALSE;
		}
	}

	/* jp2k uses page-based pyramids.
	 */
	if (vips_isprefix("VipsForeignLoadJp2k", thumbnail->loader)) {
		if (thumbnail->level_count == 0) {
			thumbnail->subifd_pyramid = FALSE;
			thumbnail->page_pyramid = TRUE;

			vips_thumbnail_get_pyramid_page(thumbnail);

			if (thumbnail->level_count == 0)
				thumbnail->page_pyramid = FALSE;
		}
	}

	/* For heif, we need to fetch the thumbnail size, in case we can use
	 * that as the source.
	 */
	if (vips_isprefix("VipsForeignLoadHeif", thumbnail->loader))
		vips_thumbnail_get_heif_thumb_info(thumbnail);

	/* We read the openslide level structure in
	 * vips_thumbnail_read_header().
	 */

	factor = 1.0;

	if (vips_isprefix("VipsForeignLoadJpeg", thumbnail->loader))
		factor = vips_thumbnail_find_jpegshrink(thumbnail,
			thumbnail->input_width, thumbnail->input_height);
	else if (vips_isprefix("VipsForeignLoadTiff", thumbnail->loader) ||
		vips_isprefix("VipsForeignLoadJp2k", thumbnail->loader) ||
		vips_isprefix("VipsForeignLoadOpenslide",
			thumbnail->loader)) {
		if (thumbnail->level_count > 0)
			factor = vips_thumbnail_find_pyrlevel(thumbnail,
				thumbnail->input_width,
				thumbnail->input_height);
	}
	else if (vips_isprefix("VipsForeignLoadWebp", thumbnail->loader)) {
		factor = vips_thumbnail_calculate_common_shrink(thumbnail,
			thumbnail->input_width,
			thumbnail->page_height);

		/* Avoid upsizing via libwebp.
		 */
		factor = VIPS_MAX(1.0, factor);
	}
	else if (vips_isprefix("VipsForeignLoadPdf", thumbnail->loader) ||
		vips_isprefix("VipsForeignLoadSvg", thumbnail->loader))
		factor = vips_thumbnail_calculate_common_shrink(thumbnail,
			thumbnail->input_width,
			thumbnail->page_height);
	else if (vips_isprefix("VipsForeignLoadHeif", thumbnail->loader)) {
		/* 'factor' is a gboolean which enables thumbnail load instead
		 * of image load.
		 *
		 * Use the thumbnail if, by using it, we could get a factor >
		 * 1.0, ie. we would not need to expand the thumbnail.
		 *
		 * Don't use >= since factor can be clipped to 1.0 under some
		 * resizing modes.
		 */
		double shrink_factor = vips_thumbnail_calculate_common_shrink(
			thumbnail,
			thumbnail->heif_thumbnail_width,
			thumbnail->heif_thumbnail_height);

		factor = shrink_factor > 1.0 ? 1 : 0;
	}

	g_info("loading with factor %g pre-shrink", factor);

	if (!(im = class->open(thumbnail, factor)))
		return NULL;

	g_info("pre-shrunk size is %d x %d", im->Xsize, im->Ysize);

	return im;
}

static int
vips_thumbnail_build(VipsObject *object)
{
	VipsThumbnail *thumbnail = VIPS_THUMBNAIL(object);
	VipsImage **t = (VipsImage **) vips_object_local_array(object, 15);

	VipsImage *in;
	int preshrunk_page_height;
	double hshrink;
	double vshrink;

	/* TRUE if we've done the import of an ICC transform and still need to
	 * export.
	 */
	gboolean have_imported;

	/* TRUE if the image needs to transformed with a pair of ICC profiles.
	 */
	gboolean needs_icc_transform;

	/* The format we need to revert to after unpremultiply.
	 */
	VipsBandFormat unpremultiplied_format;

#ifdef DEBUG
	printf("vips_thumbnail_build: ");
	vips_object_print_name(object);
	printf("\n");
#endif /*DEBUG*/

	if (VIPS_OBJECT_CLASS(vips_thumbnail_parent_class)->build(object))
		return -1;

	/* We have to support both no_rotate and auto_rotate optional args,
	 * with no_rotate being the new and not-deprecated one.
	 *
	 * If the new no_rotate flag has been set, that value overrides
	 * auto_rotate.
	 */
	if (vips_object_argument_isset(object, "no_rotate"))
		thumbnail->auto_rotate = !thumbnail->no_rotate;

	if (!vips_object_argument_isset(object, "height"))
		thumbnail->height = thumbnail->width;

	/* Open and do any pre-shrinking.
	 */
	if (!(t[0] = vips_thumbnail_open(thumbnail)))
		return -1;
	in = t[0];

	/* After pre-shrink, but before the main shrink stage.
	 */
	preshrunk_page_height = vips_image_get_page_height(in);

	needs_icc_transform = thumbnail->export_profile &&
		(thumbnail->import_profile ||
			vips_image_get_typeof(in, VIPS_META_ICC_NAME));

	/* RAD needs special unpacking.
	 */
	if (in->Coding == VIPS_CODING_RAD) {
		g_info("unpacking Rad to float");

		/* rad is scrgb.
		 */
		if (vips_rad2float(in, &t[1], NULL))
			return -1;
		in = t[1];
	}

	/* In linear mode, we need to transform to a linear space before
	 * vips_resize().
	 */
	have_imported = FALSE;
	if (thumbnail->linear) {
		/* If we are doing colour management (there's an import
		 * profile), then we can use XYZ PCS as the resize space.
		 */
		if (in->Coding == VIPS_CODING_NONE &&
			(in->BandFmt == VIPS_FORMAT_UCHAR ||
				in->BandFmt == VIPS_FORMAT_USHORT) &&
			(vips_image_get_typeof(in, VIPS_META_ICC_NAME) ||
				thumbnail->import_profile)) {
			g_info("importing to XYZ PCS");
			if (thumbnail->import_profile)
				g_info("fallback input profile %s",
					thumbnail->import_profile);

			if (vips_icc_import(in, &t[2],
					"input_profile", thumbnail->import_profile,
					"embedded", TRUE,
					"intent", thumbnail->intent,
					"pcs", VIPS_PCS_XYZ,
					NULL))
				return -1;
			in = t[2];

			have_imported = TRUE;
		}
		else {
			/* Otherwise, use scRGB or GREY16 for linear shrink.
			 */
			VipsInterpretation interpretation;

			if (in->Bands < 3)
				interpretation = VIPS_INTERPRETATION_GREY16;
			else
				interpretation = VIPS_INTERPRETATION_scRGB;

			g_info("converting to processing space %s",
				vips_enum_nick(VIPS_TYPE_INTERPRETATION,
					interpretation));
			if (vips_colourspace(in, &t[2], interpretation,
					NULL))
				return -1;
			in = t[2];
		}
	}
	else if (!needs_icc_transform) {
		/* In non-linear mode, use sRGB or B_W as the processing space
		 * but only when not transforming with a pair of ICC profiles.
		 */
		VipsInterpretation interpretation;

		if (in->Bands < 3)
			interpretation = VIPS_INTERPRETATION_B_W;
		else
			interpretation = VIPS_INTERPRETATION_sRGB;

		g_info("converting to processing space %s",
			vips_enum_nick(VIPS_TYPE_INTERPRETATION,
				interpretation));
		if (vips_colourspace(in, &t[2], interpretation,
				NULL))
			return -1;
		in = t[2];
	}

	/* Shrink to preshrunk_page_height, so we work for multi-page images.
	 */
	vips_thumbnail_calculate_shrink(thumbnail,
		in->Xsize, preshrunk_page_height, &hshrink, &vshrink);

	/* In toilet-roll mode, we must adjust vshrink so that we exactly hit
	 * page_height or we'll have pixels straddling page boundaries.
	 */
	if (in->Ysize > preshrunk_page_height) {
		int target_page_height = VIPS_RINT(
			preshrunk_page_height / vshrink);
		int target_image_height = target_page_height *
			thumbnail->n_loaded_pages;

		vshrink = (double) in->Ysize / target_image_height;
	}

	/* Both vips_premultiply() and vips_unpremultiply() produces a float
	 * image, so we must cast back to the original format. Use NOTSET
	 * to mean no pre/unmultiply.
	 */
	unpremultiplied_format = VIPS_FORMAT_NOTSET;

	/* If there's an alpha, we have to premultiply before shrinking. See
	 * https://github.com/libvips/libvips/issues/291
	 */
	if (vips_image_hasalpha(in) &&
		hshrink != 1.0 &&
		vshrink != 1.0) {
		g_info("premultiplying alpha");
		unpremultiplied_format = in->BandFmt;

		if (vips_premultiply(in, &t[3], NULL) ||
			vips_cast(t[3], &t[4], unpremultiplied_format, NULL))
			return -1;
		in = t[4];
	}

	if (vips_resize(in, &t[5], 1.0 / hshrink,
			"vscale", 1.0 / vshrink,
			NULL))
		return -1;
	in = t[5];

	if (unpremultiplied_format != VIPS_FORMAT_NOTSET) {
		g_info("unpremultiplying alpha");
		if (vips_unpremultiply(in, &t[6], NULL) ||
			vips_cast(t[6], &t[7], unpremultiplied_format, NULL))
			return -1;
		in = t[7];
	}

	/* Only set page-height if we have more than one page, or this could
	 * accidentally turn into an animated image later.
	 */
	if (thumbnail->n_loaded_pages > 1) {
		int output_page_height =
			VIPS_RINT(preshrunk_page_height / vshrink);

		if (vips_copy(in, &t[8], NULL))
			return -1;
		in = t[8];

		vips_image_set_int(in,
			VIPS_META_PAGE_HEIGHT, output_page_height);
	}

	/* Colour management.
	 */
	if (have_imported) {
		/* We are in PCS. Export with the output profile, if any (this
		 * will export with the embedded input profile if there's no
		 * export profile).
		 */
		g_info("exporting to device space with a profile");
		if (vips_icc_export(in, &t[9],
				"output_profile", thumbnail->export_profile,
				"intent", thumbnail->intent,
				NULL))
			return -1;
		in = t[9];
	}
	else if (needs_icc_transform) {
		/* We can transform to the output with a pair of ICC profiles.
		 */
		g_info("transforming with supplied profiles");
		if (vips_icc_transform(in, &t[9],
				thumbnail->export_profile,
				"input_profile", thumbnail->import_profile,
				"intent", thumbnail->intent,
				"embedded", TRUE,
				NULL))
			return -1;

		in = t[9];
	}
	else if (thumbnail->export_profile) {
		/* We are in one of the resize space (sRGB, scRGB, B_W, GREY16, etc.)
		 * and need to go to PCS, then export.
		 */
		g_info("exporting with %s", thumbnail->export_profile);
		if (vips_colourspace(in, &t[9],
				VIPS_INTERPRETATION_XYZ, NULL) ||
			vips_icc_export(t[9], &t[10],
				"output_profile", thumbnail->export_profile,
				"intent", thumbnail->intent,
				NULL))
			return -1;
		in = t[10];
	}
	else if (thumbnail->linear) {
		/* We are in one of the scRGB or GREY16 spaces and there's
		 * no export profile. Output to sRGB or B_W.
		 */
		VipsInterpretation interpretation;

		if (in->Bands < 3)
			interpretation = VIPS_INTERPRETATION_B_W;
		else
			interpretation = VIPS_INTERPRETATION_sRGB;

		g_info("converting to output space %s",
			vips_enum_nick(VIPS_TYPE_INTERPRETATION,
				interpretation));
		if (vips_colourspace(in, &t[9], interpretation,
				NULL))
			return -1;
		in = t[9];
	}

	if (thumbnail->auto_rotate &&
		thumbnail->orientation != 1) {
		g_info("rotating by EXIF orientation %d",
			thumbnail->orientation);
		/* Need to copy to memory, we have to stay seq.
		 */
		if (!(t[11] = vips_image_copy_memory(in)) ||
			vips_autorot(t[11], &t[12], NULL))
			return -1;
		in = t[12];
	}

	/* Crop after rotate so we don't need to rotate the crop box.
	 */
	if (thumbnail->crop != VIPS_INTERESTING_NONE) {
		/* The image can be smaller than the target. Adjust the
		 * arguments to vips_smartcrop().
		 */
		int crop_width = VIPS_MIN(thumbnail->width, in->Xsize);
		int crop_height = VIPS_MIN(thumbnail->height, in->Ysize);

		g_info("cropping to %dx%d", crop_width, crop_height);

		/* Need to copy to memory, we have to stay seq.
		 *
		 * FIXME ... could skip the copy if we've rotated.
		 */
		if (!(t[13] = vips_image_copy_memory(in)) ||
			vips_smartcrop(t[13], &t[14],
				crop_width, crop_height,
				"interesting", thumbnail->crop,
				NULL))
			return -1;
		in = t[14];
	}

	g_object_set(thumbnail, "out", vips_image_new(), NULL);

	if (vips_image_write(in, thumbnail->out))
		return -1;

	return 0;
}

static void
vips_thumbnail_class_init(VipsThumbnailClass *class)
{
	GObjectClass *gobject_class = G_OBJECT_CLASS(class);
	VipsObjectClass *vobject_class = VIPS_OBJECT_CLASS(class);
	VipsOperationClass *operation_class = VIPS_OPERATION_CLASS(class);

	gobject_class->dispose = vips_thumbnail_dispose;
	gobject_class->finalize = vips_thumbnail_finalize;
	gobject_class->set_property = vips_object_set_property;
	gobject_class->get_property = vips_object_get_property;

	vobject_class->nickname = "thumbnail_base";
	vobject_class->description = _("thumbnail generation");
	vobject_class->build = vips_thumbnail_build;

	/* We mustn't cache these calls, since we open the file or buffer in
	 * sequential mode.
	 */
	operation_class->flags |= VIPS_OPERATION_NOCACHE;

	VIPS_ARG_IMAGE(class, "out", 2,
		_("Output"),
		_("Output image"),
		VIPS_ARGUMENT_REQUIRED_OUTPUT,
		G_STRUCT_OFFSET(VipsThumbnail, out));

	VIPS_ARG_INT(class, "width", 3,
		_("Target width"),
		_("Size to this width"),
		VIPS_ARGUMENT_REQUIRED_INPUT,
		G_STRUCT_OFFSET(VipsThumbnail, width),
		1, VIPS_MAX_COORD, 1);

	VIPS_ARG_INT(class, "height", 113,
		_("Target height"),
		_("Size to this height"),
		VIPS_ARGUMENT_OPTIONAL_INPUT,
		G_STRUCT_OFFSET(VipsThumbnail, height),
		1, VIPS_MAX_COORD, 1);

	VIPS_ARG_ENUM(class, "size", 114,
		_("Size"),
		_("Only upsize, only downsize, or both"),
		VIPS_ARGUMENT_OPTIONAL_INPUT,
		G_STRUCT_OFFSET(VipsThumbnail, size),
		VIPS_TYPE_SIZE, VIPS_SIZE_BOTH);

	VIPS_ARG_BOOL(class, "no_rotate", 115,
		_("No rotate"),
		_("Don't use orientation tags to rotate image upright"),
		VIPS_ARGUMENT_OPTIONAL_INPUT,
		G_STRUCT_OFFSET(VipsThumbnail, no_rotate),
		FALSE);

	VIPS_ARG_ENUM(class, "crop", 116,
		_("Crop"),
		_("Reduce to fill target rectangle, then crop"),
		VIPS_ARGUMENT_OPTIONAL_INPUT,
		G_STRUCT_OFFSET(VipsThumbnail, crop),
		VIPS_TYPE_INTERESTING, VIPS_INTERESTING_NONE);

	VIPS_ARG_BOOL(class, "linear", 117,
		_("Linear"),
		_("Reduce in linear light"),
		VIPS_ARGUMENT_OPTIONAL_INPUT,
		G_STRUCT_OFFSET(VipsThumbnail, linear),
		FALSE);

	VIPS_ARG_STRING(class, "import_profile", 118,
		_("Import profile"),
		_("Fallback import profile"),
		VIPS_ARGUMENT_OPTIONAL_INPUT,
		G_STRUCT_OFFSET(VipsThumbnail, import_profile),
		NULL);

	VIPS_ARG_STRING(class, "export_profile", 119,
		_("Export profile"),
		_("Fallback export profile"),
		VIPS_ARGUMENT_OPTIONAL_INPUT,
		G_STRUCT_OFFSET(VipsThumbnail, export_profile),
		NULL);

	VIPS_ARG_ENUM(class, "intent", 120,
		_("Intent"),
		_("Rendering intent"),
		VIPS_ARGUMENT_OPTIONAL_INPUT,
		G_STRUCT_OFFSET(VipsThumbnail, intent),
		VIPS_TYPE_INTENT, VIPS_INTENT_RELATIVE);

	VIPS_ARG_ENUM(class, "fail_on", 121,
		_("Fail on"),
		_("Error level to fail on"),
		VIPS_ARGUMENT_OPTIONAL_INPUT,
		G_STRUCT_OFFSET(VipsThumbnail, fail_on),
		VIPS_TYPE_FAIL_ON, VIPS_FAIL_ON_NONE);

	/* BOOL args which default TRUE arguments don't work with the
	 * command-line -- GOption does not allow --auto-rotate=false.
	 *
	 * This is now replaced (though still functional) with "no-rotate",
	 * see above.
	 */
	VIPS_ARG_BOOL(class, "auto_rotate", 121,
		_("Auto rotate"),
		_("Use orientation tags to rotate image upright"),
		VIPS_ARGUMENT_OPTIONAL_INPUT | VIPS_ARGUMENT_DEPRECATED,
		G_STRUCT_OFFSET(VipsThumbnail, auto_rotate),
		TRUE);
}

static void
vips_thumbnail_init(VipsThumbnail *thumbnail)
{
	thumbnail->width = 1;
	thumbnail->height = 1;
	thumbnail->auto_rotate = TRUE;
	thumbnail->intent = VIPS_INTENT_RELATIVE;
	thumbnail->fail_on = VIPS_FAIL_ON_NONE;
}

typedef struct _VipsThumbnailFile {
	VipsThumbnail parent_object;

	char *filename;
} VipsThumbnailFile;

typedef VipsThumbnailClass VipsThumbnailFileClass;

G_DEFINE_TYPE(VipsThumbnailFile, vips_thumbnail_file,
	vips_thumbnail_get_type());

/* Get the info from a file.
 */
static int
vips_thumbnail_file_get_info(VipsThumbnail *thumbnail)
{
	VipsThumbnailFile *file = (VipsThumbnailFile *) thumbnail;

	VipsImage *image;

	g_info("thumbnailing %s", file->filename);

	if (!(thumbnail->loader = vips_foreign_find_load(file->filename)) ||
		!(image = vips_image_new_from_file(file->filename, NULL)))
		return -1;

	vips_thumbnail_read_header(thumbnail, image);

	g_object_unref(image);

	return 0;
}

/* Open an image, pre-shrinking as appropriate.
 */
static VipsImage *
vips_thumbnail_file_open(VipsThumbnail *thumbnail, double factor)
{
	VipsThumbnailFile *file = (VipsThumbnailFile *) thumbnail;

	if (vips_isprefix("VipsForeignLoadJpeg", thumbnail->loader)) {
		return vips_image_new_from_file(file->filename,
			"access", VIPS_ACCESS_SEQUENTIAL,
			"fail_on", thumbnail->fail_on,
			"shrink", (int) factor,
			NULL);
	}
	else if (vips_isprefix("VipsForeignLoadOpenslide",
				 thumbnail->loader)) {
		return vips_image_new_from_file(file->filename,
			"access", VIPS_ACCESS_SEQUENTIAL,
			"fail_on", thumbnail->fail_on,
			"level", (int) factor,
			NULL);
	}
	else if (vips_isprefix("VipsForeignLoadPdf", thumbnail->loader) ||
		vips_isprefix("VipsForeignLoadSvg", thumbnail->loader) ||
		vips_isprefix("VipsForeignLoadWebp", thumbnail->loader)) {
		return vips_image_new_from_file(file->filename,
			"access", VIPS_ACCESS_SEQUENTIAL,
			"fail_on", thumbnail->fail_on,
			"scale", 1.0 / factor,
			NULL);
	}
	else if (vips_isprefix("VipsForeignLoadJp2k", thumbnail->loader)) {
		/* jp2k optionally uses page-based pyramids.
		 */
		if (thumbnail->page_pyramid)
			return vips_image_new_from_file(file->filename,
				"access", VIPS_ACCESS_SEQUENTIAL,
				"fail_on", thumbnail->fail_on,
				"page", (int) factor,
				NULL);
		else
			return vips_image_new_from_file(file->filename,
				"access", VIPS_ACCESS_SEQUENTIAL,
				NULL);
	}
	else if (vips_isprefix("VipsForeignLoadTiff", thumbnail->loader)) {
		/* We support three modes: subifd pyramids, page-based
		 * pyramids, and simple multi-page TIFFs (no pyramid).
		 */
		if (thumbnail->subifd_pyramid)
			return vips_image_new_from_file(file->filename,
				"access", VIPS_ACCESS_SEQUENTIAL,
				"fail_on", thumbnail->fail_on,
				"subifd", (int) factor,
				NULL);
		else if (thumbnail->page_pyramid)
			return vips_image_new_from_file(file->filename,
				"access", VIPS_ACCESS_SEQUENTIAL,
				"fail_on", thumbnail->fail_on,
				"page", (int) factor,
				NULL);
		else
			return vips_image_new_from_file(file->filename,
				"access", VIPS_ACCESS_SEQUENTIAL,
				"fail_on", thumbnail->fail_on,
				NULL);
	}
	else if (vips_isprefix("VipsForeignLoadHeif", thumbnail->loader)) {
		return vips_image_new_from_file(file->filename,
			"access", VIPS_ACCESS_SEQUENTIAL,
			"fail_on", thumbnail->fail_on,
			"thumbnail", (int) factor,
			NULL);
	}
	else {
		return vips_image_new_from_file(file->filename,
			"access", VIPS_ACCESS_SEQUENTIAL,
			"fail_on", thumbnail->fail_on,
			NULL);
	}
}

static void
vips_thumbnail_file_class_init(VipsThumbnailClass *class)
{
	GObjectClass *gobject_class = G_OBJECT_CLASS(class);
	VipsObjectClass *vobject_class = VIPS_OBJECT_CLASS(class);
	VipsThumbnailClass *thumbnail_class = VIPS_THUMBNAIL_CLASS(class);

	gobject_class->set_property = vips_object_set_property;
	gobject_class->get_property = vips_object_get_property;

	vobject_class->nickname = "thumbnail";
	vobject_class->description = _("generate thumbnail from file");

	thumbnail_class->get_info = vips_thumbnail_file_get_info;
	thumbnail_class->open = vips_thumbnail_file_open;

	VIPS_ARG_STRING(class, "filename", 1,
		_("Filename"),
		_("Filename to read from"),
		VIPS_ARGUMENT_REQUIRED_INPUT,
		G_STRUCT_OFFSET(VipsThumbnailFile, filename),
		NULL);
}

static void
vips_thumbnail_file_init(VipsThumbnailFile *file)
{
}

/**
 * vips_thumbnail:
 * @filename: file to read from
 * @out: (out): output image
 * @width: target width in pixels
 * @...: %NULL-terminated list of optional named arguments
 *
 * Optional arguments:
 *
 * * @height: %gint, target height in pixels
 * * @size: #VipsSize, upsize, downsize, both or force
 * * @no_rotate: %gboolean, don't rotate upright using orientation tag
 * * @crop: #VipsInteresting, shrink and crop to fill target
 * * @linear: %gboolean, perform shrink in linear light
 * * @import_profile: %gchararray, fallback import ICC profile
 * * @export_profile: %gchararray, export ICC profile
 * * @intent: #VipsIntent, rendering intent
 * * @fail_on: #VipsFailOn, load error types to fail on
 *
 * Make a thumbnail from a file. Shrinking is done in three stages: using any
 * shrink-on-load features available in the file import library, using a block
 * shrink, and using a lanczos3 shrink. At least the final 200% is done with
 * lanczos3. The output should be high quality, and the operation should be
 * quick.
 *
 * See vips_thumbnail_buffer() to thumbnail from a memory buffer, or
 * vips_thumbnail_source() to thumbnail from an arbitrary byte source.
 *
 * By default, libvips will only the first frame of animated or multipage
 * images. To thumbnail all pages or frames, pass `n=-1` to the loader in
 * @filename, for example `"x.gif[n=-1]"`.
 *
 * The output image will fit within a square of size @width x @width. You can
 * specify a separate height with the @height option. Set either @width or
 * @height to a very large number to ignore that dimension.
 *
 * If you set @crop, then the output image will fill the whole of the @width x
 * @height rectangle, with any excess cropped away. See vips_smartcrop() for
 * details on the cropping strategy.
 *
 * Normally the operation will upsize or downsize as required to fit the image
 * inside or outside the target size. If @size is set
 * to #VIPS_SIZE_UP, the operation will only upsize and will just
 * copy if asked to downsize.
 * If @size is set
 * to #VIPS_SIZE_DOWN, the operation will only downsize and will just
 * copy if asked to upsize.
 * If @size is #VIPS_SIZE_FORCE, the image aspect ratio will be broken and the
 * image will be forced to fit the target.
 *
 * Normally any orientation tags on the input image (such as EXIF tags) are
 * interpreted to rotate the image upright. If you set @no_rotate to %TRUE,
 * these tags will not be interpreted.
 *
 * Shrinking is normally done in sRGB colourspace. Set @linear to shrink in
 * linear light colourspace instead. This can give better results, but can
 * also be far slower, since tricks like JPEG shrink-on-load cannot be used in
 * linear space.
 *
 * If you set @export_profile to the filename of an ICC profile, the image
 * will be transformed to the target colourspace before writing to the
 * output. You can also give an @import_profile which will be used if the
 * input image has no ICC profile, or if the profile embedded in the
 * input image is broken.
 *
 * Use @intent to set the rendering intent for any ICC transform. The default
 * is #VIPS_INTENT_RELATIVE.
 *
 * Use @fail_on to control the types of error that will cause loading to fail.
 * The default is #VIPS_FAIL_ON_NONE, ie. thumbnail is permissive.
 *
 * See also: vips_thumbnail_buffer().
 *
 * Returns: 0 on success, -1 on error.
 */
int
vips_thumbnail(const char *filename, VipsImage **out, int width, ...)
{
	va_list ap;
	int result;

	va_start(ap, width);
	result = vips_call_split("thumbnail", ap, filename, out, width);
	va_end(ap);

	return result;
}

typedef struct _VipsThumbnailBuffer {
	VipsThumbnail parent_object;

	VipsArea *buf;
	char *option_string;
} VipsThumbnailBuffer;

typedef VipsThumbnailClass VipsThumbnailBufferClass;

G_DEFINE_TYPE(VipsThumbnailBuffer, vips_thumbnail_buffer,
	vips_thumbnail_get_type());

/* Get the info from a buffer.
 */
static int
vips_thumbnail_buffer_get_info(VipsThumbnail *thumbnail)
{
	VipsThumbnailBuffer *buffer = (VipsThumbnailBuffer *) thumbnail;

	VipsImage *image;

	g_info("thumbnailing %zd bytes of data", buffer->buf->length);

	if (!(thumbnail->loader = vips_foreign_find_load_buffer(
			  buffer->buf->data, buffer->buf->length)) ||
		!(image = vips_image_new_from_buffer(
			  buffer->buf->data, buffer->buf->length,
			  buffer->option_string, NULL)))
		return -1;

	vips_thumbnail_read_header(thumbnail, image);

	g_object_unref(image);

	return 0;
}

/* Open an image, scaling as appropriate.
 */
static VipsImage *
vips_thumbnail_buffer_open(VipsThumbnail *thumbnail, double factor)
{
	VipsThumbnailBuffer *buffer = (VipsThumbnailBuffer *) thumbnail;

	if (vips_isprefix("VipsForeignLoadJpeg", thumbnail->loader)) {
		return vips_image_new_from_buffer(
			buffer->buf->data, buffer->buf->length,
			buffer->option_string,
			"access", VIPS_ACCESS_SEQUENTIAL,
			"shrink", (int) factor,
			NULL);
	}
	else if (vips_isprefix("VipsForeignLoadOpenslide",
				 thumbnail->loader)) {
		return vips_image_new_from_buffer(
			buffer->buf->data, buffer->buf->length,
			buffer->option_string,
			"access", VIPS_ACCESS_SEQUENTIAL,
			"level", (int) factor,
			NULL);
	}
	else if (vips_isprefix("VipsForeignLoadPdf", thumbnail->loader) ||
		vips_isprefix("VipsForeignLoadSvg", thumbnail->loader) ||
		vips_isprefix("VipsForeignLoadWebp", thumbnail->loader)) {
		return vips_image_new_from_buffer(
			buffer->buf->data, buffer->buf->length,
			buffer->option_string,
			"access", VIPS_ACCESS_SEQUENTIAL,
			"scale", 1.0 / factor,
			NULL);
	}
	else if (vips_isprefix("VipsForeignLoadJp2k", thumbnail->loader)) {
		/* Optional page-based pyramids.
		 */
		if (thumbnail->page_pyramid)
			return vips_image_new_from_buffer(
				buffer->buf->data, buffer->buf->length,
				buffer->option_string,
				"access", VIPS_ACCESS_SEQUENTIAL,
				"page", (int) factor,
				NULL);
		else
			return vips_image_new_from_buffer(
				buffer->buf->data, buffer->buf->length,
				buffer->option_string,
				"access", VIPS_ACCESS_SEQUENTIAL,
				NULL);
	}
	else if (vips_isprefix("VipsForeignLoadTiff", thumbnail->loader)) {
		/* We support three modes: subifd pyramids, page-based
		 * pyramids, and simple multi-page TIFFs (no pyramid).
		 */
		if (thumbnail->subifd_pyramid)
			return vips_image_new_from_buffer(
				buffer->buf->data, buffer->buf->length,
				buffer->option_string,
				"access", VIPS_ACCESS_SEQUENTIAL,
				"subifd", (int) factor,
				NULL);
		else if (thumbnail->page_pyramid)
			return vips_image_new_from_buffer(
				buffer->buf->data, buffer->buf->length,
				buffer->option_string,
				"access", VIPS_ACCESS_SEQUENTIAL,
				"page", (int) factor,
				NULL);
		else
			return vips_image_new_from_buffer(
				buffer->buf->data, buffer->buf->length,
				buffer->option_string,
				"access", VIPS_ACCESS_SEQUENTIAL,
				NULL);
	}
	else if (vips_isprefix("VipsForeignLoadHeif", thumbnail->loader)) {
		return vips_image_new_from_buffer(
			buffer->buf->data, buffer->buf->length,
			buffer->option_string,
			"access", VIPS_ACCESS_SEQUENTIAL,
			"thumbnail", (int) factor,
			NULL);
	}
	else {
		return vips_image_new_from_buffer(
			buffer->buf->data, buffer->buf->length,
			buffer->option_string,
			"access", VIPS_ACCESS_SEQUENTIAL,
			NULL);
	}
}

static void
vips_thumbnail_buffer_class_init(VipsThumbnailClass *class)
{
	GObjectClass *gobject_class = G_OBJECT_CLASS(class);
	VipsObjectClass *vobject_class = VIPS_OBJECT_CLASS(class);
	VipsThumbnailClass *thumbnail_class = VIPS_THUMBNAIL_CLASS(class);

	gobject_class->set_property = vips_object_set_property;
	gobject_class->get_property = vips_object_get_property;

	vobject_class->nickname = "thumbnail_buffer";
	vobject_class->description = _("generate thumbnail from buffer");

	thumbnail_class->get_info = vips_thumbnail_buffer_get_info;
	thumbnail_class->open = vips_thumbnail_buffer_open;

	VIPS_ARG_BOXED(class, "buffer", 1,
		_("Buffer"),
		_("Buffer to load from"),
		VIPS_ARGUMENT_REQUIRED_INPUT,
		G_STRUCT_OFFSET(VipsThumbnailBuffer, buf),
		VIPS_TYPE_BLOB);

	VIPS_ARG_STRING(class, "option_string", 20,
		_("Extra options"),
		_("Options that are passed on to the underlying loader"),
		VIPS_ARGUMENT_OPTIONAL_INPUT,
		G_STRUCT_OFFSET(VipsThumbnailBuffer, option_string),
		"");
}

static void
vips_thumbnail_buffer_init(VipsThumbnailBuffer *buffer)
{
}

/**
 * vips_thumbnail_buffer:
 * @buf: (array length=len) (element-type guint8): memory area to load
 * @len: (type gsize): size of memory area
 * @out: (out): output image
 * @width: target width in pixels
 * @...: %NULL-terminated list of optional named arguments
 *
 * Optional arguments:
 *
 * * @height: %gint, target height in pixels
 * * @size: #VipsSize, upsize, downsize, both or force
 * * @no_rotate: %gboolean, don't rotate upright using orientation tag
 * * @crop: #VipsInteresting, shrink and crop to fill target
 * * @linear: %gboolean, perform shrink in linear light
 * * @import_profile: %gchararray, fallback import ICC profile
 * * @export_profile: %gchararray, export ICC profile
 * * @intent: #VipsIntent, rendering intent
 * * @fail_on: #VipsFailOn, load error types to fail on
 * * @option_string: %gchararray, extra loader options
 *
 * Exactly as vips_thumbnail(), but read from a memory buffer. One extra
 * optional argument, @option_string, lets you pass options to the underlying
 * loader.
 *
 * See also: vips_thumbnail().
 *
 * Returns: 0 on success, -1 on error.
 */
int
vips_thumbnail_buffer(void *buf, size_t len, VipsImage **out, int width, ...)
{
	va_list ap;
	VipsBlob *blob;
	int result;

	/* We don't take a copy of the data or free it.
	 */
	blob = vips_blob_new(NULL, buf, len);

	va_start(ap, width);
	result = vips_call_split("thumbnail_buffer", ap, blob, out, width);
	va_end(ap);

	vips_area_unref(VIPS_AREA(blob));

	return result;
}

typedef struct _VipsThumbnailSource {
	VipsThumbnail parent_object;

	VipsSource *source;
	char *option_string;
} VipsThumbnailSource;

typedef VipsThumbnailClass VipsThumbnailSourceClass;

G_DEFINE_TYPE(VipsThumbnailSource, vips_thumbnail_source,
	vips_thumbnail_get_type());

/* Get the info from a source.
 */
static int
vips_thumbnail_source_get_info(VipsThumbnail *thumbnail)
{
	VipsThumbnailSource *source = (VipsThumbnailSource *) thumbnail;

	VipsImage *image;

	g_info("thumbnailing source");

	if (!(thumbnail->loader = vips_foreign_find_load_source(
			  source->source)) ||
		!(image = vips_image_new_from_source(source->source,
			  source->option_string, NULL)))
		return -1;

	vips_thumbnail_read_header(thumbnail, image);

	g_object_unref(image);

	return 0;
}

/* Open an image, scaling as appropriate.
 */
static VipsImage *
vips_thumbnail_source_open(VipsThumbnail *thumbnail, double factor)
{
	VipsThumbnailSource *source = (VipsThumbnailSource *) thumbnail;

	if (vips_isprefix("VipsForeignLoadJpeg", thumbnail->loader)) {
		return vips_image_new_from_source(
			source->source,
			source->option_string,
			"access", VIPS_ACCESS_SEQUENTIAL,
			"shrink", (int) factor,
			NULL);
	}
	else if (vips_isprefix("VipsForeignLoadOpenslide",
				 thumbnail->loader)) {
		return vips_image_new_from_source(
			source->source,
			source->option_string,
			"access", VIPS_ACCESS_SEQUENTIAL,
			"level", (int) factor,
			NULL);
	}
	else if (vips_isprefix("VipsForeignLoadPdf", thumbnail->loader) ||
		vips_isprefix("VipsForeignLoadSvg", thumbnail->loader) ||
		vips_isprefix("VipsForeignLoadWebp", thumbnail->loader)) {
		return vips_image_new_from_source(
			source->source,
			source->option_string,
			"access", VIPS_ACCESS_SEQUENTIAL,
			"scale", 1.0 / factor,
			NULL);
	}
	else if (vips_isprefix("VipsForeignLoadJp2k", thumbnail->loader)) {
		/* Optional page-based pyramids.
		 */
		if (thumbnail->page_pyramid)
			return vips_image_new_from_source(
				source->source,
				source->option_string,
				"access", VIPS_ACCESS_SEQUENTIAL,
				"page", (int) factor,
				NULL);
		else
			return vips_image_new_from_source(
				source->source,
				source->option_string,
				"access", VIPS_ACCESS_SEQUENTIAL,
				NULL);
	}
	else if (vips_isprefix("VipsForeignLoadTiff", thumbnail->loader)) {
		/* We support three modes: subifd pyramids, page-based
		 * pyramids, and simple multi-page TIFFs (no pyramid).
		 */
		if (thumbnail->subifd_pyramid)
			return vips_image_new_from_source(
				source->source,
				source->option_string,
				"access", VIPS_ACCESS_SEQUENTIAL,
				"subifd", (int) factor,
				NULL);
		else if (thumbnail->page_pyramid)
			return vips_image_new_from_source(
				source->source,
				source->option_string,
				"access", VIPS_ACCESS_SEQUENTIAL,
				"page", (int) factor,
				NULL);
		else
			return vips_image_new_from_source(
				source->source,
				source->option_string,
				"access", VIPS_ACCESS_SEQUENTIAL,
				NULL);
	}
	else if (vips_isprefix("VipsForeignLoadHeif", thumbnail->loader)) {
		return vips_image_new_from_source(
			source->source,
			source->option_string,
			"access", VIPS_ACCESS_SEQUENTIAL,
			"thumbnail", (int) factor,
			NULL);
	}
	else {
		return vips_image_new_from_source(
			source->source,
			source->option_string,
			"access", VIPS_ACCESS_SEQUENTIAL,
			NULL);
	}
}

static void
vips_thumbnail_source_class_init(VipsThumbnailClass *class)
{
	GObjectClass *gobject_class = G_OBJECT_CLASS(class);
	VipsObjectClass *vobject_class = VIPS_OBJECT_CLASS(class);
	VipsThumbnailClass *thumbnail_class = VIPS_THUMBNAIL_CLASS(class);

	gobject_class->set_property = vips_object_set_property;
	gobject_class->get_property = vips_object_get_property;

	vobject_class->nickname = "thumbnail_source";
	vobject_class->description = _("generate thumbnail from source");

	thumbnail_class->get_info = vips_thumbnail_source_get_info;
	thumbnail_class->open = vips_thumbnail_source_open;

	VIPS_ARG_OBJECT(class, "source", 1,
		_("Source"),
		_("Source to load from"),
		VIPS_ARGUMENT_REQUIRED_INPUT,
		G_STRUCT_OFFSET(VipsThumbnailSource, source),
		VIPS_TYPE_SOURCE);

	VIPS_ARG_STRING(class, "option_string", 20,
		_("Extra options"),
		_("Options that are passed on to the underlying loader"),
		VIPS_ARGUMENT_OPTIONAL_INPUT,
		G_STRUCT_OFFSET(VipsThumbnailSource, option_string),
		"");
}

static void
vips_thumbnail_source_init(VipsThumbnailSource *source)
{
}

/**
 * vips_thumbnail_source:
 * @source: source to thumbnail
 * @out: (out): output image
 * @width: target width in pixels
 * @...: %NULL-terminated list of optional named arguments
 *
 * Optional arguments:
 *
 * * @height: %gint, target height in pixels
 * * @size: #VipsSize, upsize, downsize, both or force
 * * @no_rotate: %gboolean, don't rotate upright using orientation tag
 * * @crop: #VipsInteresting, shrink and crop to fill target
 * * @linear: %gboolean, perform shrink in linear light
 * * @import_profile: %gchararray, fallback import ICC profile
 * * @export_profile: %gchararray, export ICC profile
 * * @intent: #VipsIntent, rendering intent
 * * @fail_on: #VipsFailOn, load error types to fail on
 * * @option_string: %gchararray, extra loader options
 *
 * Exactly as vips_thumbnail(), but read from a source. One extra
 * optional argument, @option_string, lets you pass options to the underlying
 * loader.
 *
 * See also: vips_thumbnail().
 *
 * Returns: 0 on success, -1 on error.
 */
int
vips_thumbnail_source(VipsSource *source, VipsImage **out, int width, ...)
{
	va_list ap;
	int result;

	va_start(ap, width);
	result = vips_call_split("thumbnail_source", ap, source, out, width);
	va_end(ap);

	return result;
}

typedef struct _VipsThumbnailImage {
	VipsThumbnail parent_object;

	VipsImage *in;
} VipsThumbnailImage;

typedef VipsThumbnailClass VipsThumbnailImageClass;

G_DEFINE_TYPE(VipsThumbnailImage, vips_thumbnail_image,
	vips_thumbnail_get_type());

/* Get the info from a image.
 */
static int
vips_thumbnail_image_get_info(VipsThumbnail *thumbnail)
{
	VipsThumbnailImage *image = (VipsThumbnailImage *) thumbnail;

	/* Doesn't really matter what we put here.
	 */
	thumbnail->loader = "image source";

	vips_thumbnail_read_header(thumbnail, image->in);

	return 0;
}

/* Open an image. We can't pre-shrink with an image source, sadly.
 */
static VipsImage *
vips_thumbnail_image_open(VipsThumbnail *thumbnail, double factor)
{
	VipsThumbnailImage *image = (VipsThumbnailImage *) thumbnail;
	VipsImage **t = (VipsImage **)
		vips_object_local_array(VIPS_OBJECT(thumbnail), 1);

	/* We want thumbnail to run in sequential mode on this image, or we
	 * may get horrible cache thrashing.
	 */
	if (vips_sequential(image->in, &t[0], "tile-height", 16, NULL))
		return NULL;

	g_object_ref(t[0]);

	return t[0];
}

static void
vips_thumbnail_image_class_init(VipsThumbnailClass *class)
{
	GObjectClass *gobject_class = G_OBJECT_CLASS(class);
	VipsObjectClass *vobject_class = VIPS_OBJECT_CLASS(class);
	VipsThumbnailClass *thumbnail_class = VIPS_THUMBNAIL_CLASS(class);

	gobject_class->set_property = vips_object_set_property;
	gobject_class->get_property = vips_object_get_property;

	vobject_class->nickname = "thumbnail_image";
	vobject_class->description = _("generate thumbnail from image");

	thumbnail_class->get_info = vips_thumbnail_image_get_info;
	thumbnail_class->open = vips_thumbnail_image_open;

	VIPS_ARG_IMAGE(class, "in", 1,
		_("Input"),
		_("Input image argument"),
		VIPS_ARGUMENT_REQUIRED_INPUT,
		G_STRUCT_OFFSET(VipsThumbnailImage, in));
}

static void
vips_thumbnail_image_init(VipsThumbnailImage *image)
{
}

/**
 * vips_thumbnail_image: (method)
 * @in: input image
 * @out: (out): output image
 * @width: target width in pixels
 * @...: %NULL-terminated list of optional named arguments
 *
 * Optional arguments:
 *
 * * @height: %gint, target height in pixels
 * * @size: #VipsSize, upsize, downsize, both or force
 * * @no_rotate: %gboolean, don't rotate upright using orientation tag
 * * @crop: #VipsInteresting, shrink and crop to fill target
 * * @linear: %gboolean, perform shrink in linear light
 * * @import_profile: %gchararray, fallback import ICC profile
 * * @export_profile: %gchararray, export ICC profile
 * * @intent: #VipsIntent, rendering intent
 * * @fail_on: #VipsFailOn, load error types to fail on
 *
 * Exactly as vips_thumbnail(), but read from an existing image.
 *
 * This operation
 * is not able to exploit shrink-on-load features of image load libraries, so
 * it can be much slower than `vips_thumbnail()` and produce poorer quality
 * output. Only use it if you really have to.
 *
 * See also: vips_thumbnail().
 *
 * Returns: 0 on success, -1 on error.
 */
int
vips_thumbnail_image(VipsImage *in, VipsImage **out, int width, ...)
{
	va_list ap;
	int result;

	va_start(ap, width);
	result = vips_call_split("thumbnail_image", ap, in, out, width);
	va_end(ap);

	return result;
}
