Merge branch 'master' into revise-composite

ChangeLog

@@ -37,6 +37,7 @@
 - dzsave to szi will write all associated images
 - remove old c++ and python interfaces
 - vipsthumbnail can thumbnail animated and multipage images
+- deprecate webpload @shrink, use @scale instead
 
 31/3/19 started 8.7.5
 - better buffer sizing in tiff reader [omira-sch]

libvips/foreign/magicksave.c

@@ -143,9 +143,18 @@ vips_foreign_save_magick_next_image( VipsForeignSaveMagick *magick )
 		!vips_image_get_int( im, "gif-delay", &number ) )
 		image->delay = (size_t) number;
 
+	/* ImageMagick uses iterations like this (at least in gif save):
+	 * 	0 - set 0 loops (infinite)
+	 * 	1 - don't write the netscape extension block
+	 * 	2 - loop once
+	 * 	3 - loop twice etc.
+	 *
+	 * We have the simple gif meaning, so we must add one unless it's
+	 * zero.
+	 */
 	if( vips_image_get_typeof( im, "gif-loop" ) &&
 		!vips_image_get_int( im, "gif-loop", &number ) )
-		image->iterations = (size_t) number;
+		image->iterations = (size_t) (number ? number + 1 : 0);
 
 	if( vips_image_get_typeof( im, "gif-comment" ) &&
 		!vips_image_get_string( im, "gif-comment", &str ) )

libvips/foreign/pdfload.c

@@ -297,8 +297,12 @@ vips_foreign_load_pdf_header( VipsForeignLoad *load )
 		poppler_page_get_size( pdf->page, &width, &height ); 
 		pdf->pages[i].left = 0;
 		pdf->pages[i].top = top;
-		pdf->pages[i].width = width * pdf->scale;
+		/* We do round to nearest, in the same way that vips_resize()
-		pdf->pages[i].height = height * pdf->scale;
+		 * does round to nearest. Without this, things like
+		 * shrink-on-load will break.
+		 */
+		pdf->pages[i].width = VIPS_RINT( width * pdf->scale );
+		pdf->pages[i].height = VIPS_RINT( height * pdf->scale );
 
 		if( pdf->pages[i].width > pdf->image.width )
 			pdf->image.width = pdf->pages[i].width;

libvips/foreign/pdfload_pdfium.c

@@ -341,10 +341,14 @@ vips_foreign_load_pdf_header( VipsForeignLoad *load )
 			return( -1 );
 		pdf->pages[i].left = 0;
 		pdf->pages[i].top = top;
-		pdf->pages[i].width = 
+		/* We do round to nearest, in the same way that vips_resize()
-			FPDF_GetPageWidth( pdf->page ) * pdf->scale;
+		 * does round to nearest. Without this, things like
-		pdf->pages[i].height = 
+		 * shrink-on-load will break.
-			FPDF_GetPageHeight( pdf->page ) * pdf->scale;
+		 */
+		pdf->pages[i].width = VIPS_RINT( 
+			FPDF_GetPageWidth( pdf->page ) * pdf->scale );
+		pdf->pages[i].height = VIPS_RINT( 
+			FPDF_GetPageHeight( pdf->page ) * pdf->scale );
 
 		if( pdf->pages[i].width > pdf->image.width )
 			pdf->image.width = pdf->pages[i].width;

libvips/foreign/pforeign.h

@@ -226,14 +226,14 @@ int vips__iswebp_buffer( const void *buf, size_t len );
 int vips__iswebp( const char *filename );
 
 int vips__webp_read_file_header( const char *name, VipsImage *out, 
-	int page, int n, int shrink ); 
+	int page, int n, double scale ); 
 int vips__webp_read_file( const char *name, VipsImage *out, 
-	int page, int n, int shrink ); 
+	int page, int n, double scale ); 
 
 int vips__webp_read_buffer_header( const void *buf, size_t len, VipsImage *out,
-	int page, int n, int shrink ); 
+	int page, int n, double scale ); 
 int vips__webp_read_buffer( const void *buf, size_t len, VipsImage *out, 
-	int page, int n, int shrink ); 
+	int page, int n, double scale ); 
 
 int vips__webp_write_file( VipsImage *out, const char *filename, 
 	int Q, gboolean lossless, VipsForeignWebpPreset preset,

libvips/foreign/tiff2vips.c

@@ -2345,25 +2345,7 @@ rtiff_new_buffer( const void *buf, size_t len, VipsImage *out,
 	return( rtiff );
 }
 
-/* 
+/* For istiffpyramid(), see vips_thumbnail_get_tiff_pyramid().
-
-	FIXME ... Unused for now, perhaps if we add another format flag.
-
-static int
-istiffpyramid( const char *name )
-{
-	TIFF *tif;
-
-	vips__tiff_init();
-
-	if( (tif = get_directory( name, 2 )) ) {
-		// We can see page 2 ... assume it is.
-		TIFFClose( tif );
-		return( 1 );
-	}
-
-	return( 0 );
-}
  */
 
 int
@@ -2379,7 +2361,8 @@ vips__tiff_read( const char *filename, VipsImage *out,
 
 	vips__tiff_init();
 
-	if( !(rtiff = rtiff_new_filename( filename, out, page, n, autorotate )) )
+	if( !(rtiff = rtiff_new_filename( filename, out, 
+		page, n, autorotate )) )
 		return( -1 );
 
 	if( rtiff->header.tiled ) {
@@ -2394,7 +2377,7 @@ vips__tiff_read( const char *filename, VipsImage *out,
 	return( 0 );
 }
 
-/* On a header-only read, we can just swap width/height if orientaion is 6 or
+/* On a header-only read, we can just swap width/height if orientation is 6 or
  * 8. 
  */
 static void

libvips/foreign/webp2vips.c

@@ -17,6 +17,9 @@
  * 	- could memleak on some read errors
  * 24/4/19
  * 	- fix bg handling in animations
+ * 30/4/19
+ * 	- deprecate shrink, use scale instead, and make it a double ... this
+ * 	  lets us do faster and more accurate thumbnailing
  */
 
 /*
@@ -90,9 +93,9 @@ typedef struct {
 	 */
 	int n;
 
-	/* Shrink-on-load factor. Use this to set scaled_width.
+	/* Scale-on-load factor. Use this to set scaled_width.
 	 */
-	int shrink;
+	double scale;
 
 	/* Size of final output image. 
 	 */
@@ -150,6 +153,39 @@ typedef struct {
 	VipsRect dispose_rect;
 } Read;
 
+const char *
+vips__error_webp( VP8StatusCode code )
+{
+	switch( code ) {
+	case VP8_STATUS_OK: 
+		return( "VP8_STATUS_OK" );
+
+	case VP8_STATUS_OUT_OF_MEMORY:
+		return( "VP8_STATUS_OUT_OF_MEMORY" );
+
+	case VP8_STATUS_INVALID_PARAM:
+		return( "VP8_STATUS_INVALID_PARAM" );
+
+	case VP8_STATUS_BITSTREAM_ERROR:
+		return( "VP8_STATUS_BITSTREAM_ERROR" );
+
+	case VP8_STATUS_UNSUPPORTED_FEATURE:
+		return( "VP8_STATUS_UNSUPPORTED_FEATURE" );
+
+	case VP8_STATUS_SUSPENDED:
+		return( "VP8_STATUS_SUSPENDED" );
+
+	case VP8_STATUS_USER_ABORT:
+		return( "VP8_STATUS_USER_ABORT" );
+
+	case VP8_STATUS_NOT_ENOUGH_DATA:
+		return( "VP8_STATUS_NOT_ENOUGH_DATA" );
+
+	default:
+		return( "<unkown>" );
+	}
+}
+
 static void
 vips_image_paint_area( VipsImage *image, const VipsRect *r, const VipsPel *ink )
 {
@@ -230,32 +266,34 @@ blend_pixel( guint32 A, guint32 B )
 	return( setRGBA( rR, gR, bR, aR ) ); 
 }
 
+/* Blend sub into frame at left, top.
+ */
 static void
-vips_image_paint_image( VipsImage *image, 
+vips_image_paint_image( VipsImage *frame, 
-	VipsImage *ink, int x, int y, gboolean blend )
+	VipsImage *sub, int left, int top, gboolean blend )
 {
-	VipsRect valid = { 0, 0, image->Xsize, image->Ysize };
+	VipsRect frame_rect = { 0, 0, frame->Xsize, frame->Ysize };
-	VipsRect sub = { x, y, ink->Xsize, ink->Ysize };
+	VipsRect sub_rect = { left, top, sub->Xsize, sub->Ysize };
-	int ps = VIPS_IMAGE_SIZEOF_PEL( image );
+	int ps = VIPS_IMAGE_SIZEOF_PEL( frame );
 
 	VipsRect ovl;
 
-	g_assert( VIPS_IMAGE_SIZEOF_PEL( ink ) == ps );
+	g_assert( VIPS_IMAGE_SIZEOF_PEL( sub ) == ps );
 
 	/* Disable blend if we are not RGBA.
 	 */
-	if( image->Bands != 4 )
+	if( frame->Bands != 4 )
 		blend = FALSE;
 
-	vips_rect_intersectrect( &valid, &sub, &ovl );
+	vips_rect_intersectrect( &frame_rect, &sub_rect, &ovl );
 	if( !vips_rect_isempty( &ovl ) ) {
 		VipsPel *p, *q;
-		int i;
+		int x, y;
 
-		p = VIPS_IMAGE_ADDR( ink, ovl.left - x, ovl.top - y );
+		p = VIPS_IMAGE_ADDR( sub, ovl.left - left, ovl.top - top );
-		q = VIPS_IMAGE_ADDR( image, ovl.left, ovl.top ); 
+		q = VIPS_IMAGE_ADDR( frame, ovl.left, ovl.top ); 
 
-		for( i = 0; i < ovl.height; i++ ) { 
+		for( y = 0; y < ovl.height; y++ ) { 
 			if( blend ) {
 				guint32 *A = (guint32 *) p;
 				guint32 *B = (guint32 *) q;
@@ -267,8 +305,8 @@ vips_image_paint_image( VipsImage *image,
 				memcpy( (char *) q, (char *) p, 
 					ovl.width * ps );
 
-			p += VIPS_IMAGE_SIZEOF_LINE( ink );
+			p += VIPS_IMAGE_SIZEOF_LINE( sub );
-			q += VIPS_IMAGE_SIZEOF_LINE( image );
+			q += VIPS_IMAGE_SIZEOF_LINE( frame );
 		}
 	}
 }
@@ -325,7 +363,7 @@ read_free( Read *read )
 
 static Read *
 read_new( const char *filename, const void *data, size_t length, 
-	int page, int n, int shrink )
+	int page, int n, double scale )
 {
 	Read *read;
 
@@ -337,7 +375,7 @@ read_new( const char *filename, const void *data, size_t length,
 	read->length = length;
 	read->page = page;
 	read->n = n;
-	read->shrink = shrink;
+	read->scale = scale;
 	read->delay = 100;
 	read->fd = 0;
 	read->demux = NULL;
@@ -394,14 +432,17 @@ read_header( Read *read, VipsImage *out )
 
 	canvas_width = WebPDemuxGetI( read->demux, WEBP_FF_CANVAS_WIDTH );
 	canvas_height = WebPDemuxGetI( read->demux, WEBP_FF_CANVAS_HEIGHT );
-	read->frame_width = canvas_width / read->shrink;
+	/* We round-to-nearest cf. pdfload etc.
-	read->frame_height = canvas_height / read->shrink;
+	 */
+	read->frame_width = VIPS_RINT( canvas_width * read->scale );
+	read->frame_height = VIPS_RINT( canvas_height * read->scale );
 
-	if( read->shrink > 1 ) { 
+#ifdef DEBUG
-		read->config.options.use_scaling = 1;
+	printf( "webp2vips: canvas_width = %d\n", canvas_width );
-		read->config.options.scaled_width = read->frame_width;
+	printf( "webp2vips: canvas_height = %d\n", canvas_height );
-		read->config.options.scaled_height = read->frame_height; 
+	printf( "webp2vips: frame_width = %d\n", read->frame_width );
-	}
+	printf( "webp2vips: frame_height = %d\n", read->frame_height );
+#endif /*DEBUG*/
 
 	flags = WebPDemuxGetI( read->demux, WEBP_FF_FORMAT_FLAGS );
 
@@ -521,11 +562,11 @@ read_header( Read *read, VipsImage *out )
 
 int
 vips__webp_read_file_header( const char *filename, VipsImage *out, 
-	int page, int n, int shrink )
+	int page, int n, double scale )
 {
 	Read *read;
 
-	if( !(read = read_new( filename, NULL, 0, page, n, shrink )) ) {
+	if( !(read = read_new( filename, NULL, 0, page, n, scale )) ) {
 		vips_error( "webp2vips",
 			_( "unable to open \"%s\"" ), filename ); 
 		return( -1 );
@@ -541,6 +582,9 @@ vips__webp_read_file_header( const char *filename, VipsImage *out,
 	return( 0 );
 }
 
+/* Read a single frame -- a width * height block of pixels. This will get
+ * blended into the accumulator at some offset.
+ */
 static VipsImage *
 read_frame( Read *read, 
 	int width, int height, const guint8 *data, size_t length )
@@ -568,6 +612,11 @@ read_frame( Read *read,
 	read->config.output.u.RGBA.rgba = VIPS_IMAGE_ADDR( frame, 0, 0 );
 	read->config.output.u.RGBA.stride = VIPS_IMAGE_SIZEOF_LINE( frame );
 	read->config.output.u.RGBA.size = VIPS_IMAGE_SIZEOF_IMAGE( frame );
+	if( read->scale != 1.0 ) { 
+		read->config.options.use_scaling = 1;
+		read->config.options.scaled_width = width;
+		read->config.options.scaled_height = height; 
+	}
 
 	if( WebPDecode( data, length, &read->config ) != VP8_STATUS_OK ) {
 		g_object_unref( frame );
@@ -582,16 +631,26 @@ static int
 read_next_frame( Read *read )
 {
 	VipsImage *frame;
+	VipsRect area;
 
 #ifdef DEBUG
 	printf( "read_next_frame:\n" ); 
 #endif /*DEBUG*/
 
+	/* Area of this frame, in output image coordinates. We must rint(),
+	 * since we need the same rules as the overall image scale, or we'll
+	 * sometimes have missing pixels on edges.
+	 */
+	area.left = VIPS_RINT( read->iter.x_offset * read->scale ); 
+	area.top = VIPS_RINT( read->iter.y_offset * read->scale );
+	area.width = VIPS_RINT( read->iter.width * read->scale );
+	area.height = VIPS_RINT( read->iter.height * read->scale );
+
 	/* Dispose from the previous frame.
 	 */
 	if( read->dispose_method == WEBP_MUX_DISPOSE_BACKGROUND ) {
-		/* We must clear the pixels occupied by this webp frame (not 
+		/* We must clear the pixels occupied by the previous webp 
-		 * the whole of the read frame) to 0 (transparent). 
+		 * frame (not the whole of the read frame) to 0 (transparent). 
 		 *
 		 * We do not clear to WEBP_FF_BACKGROUND_COLOR. That's only 
 		 * used to composite down to RGB. Perhaps we
@@ -606,17 +665,14 @@ read_next_frame( Read *read )
 	/* Note this frame's dispose for next time.
 	 */
 	read->dispose_method = read->iter.dispose_method;
-	read->dispose_rect.left = read->iter.x_offset; 
+	read->dispose_rect = area;
-	read->dispose_rect.top = read->iter.y_offset;
-	read->dispose_rect.width = read->iter.width;
-	read->dispose_rect.height = read->iter.height;
 
 #ifdef DEBUG
 	printf( "webp2vips: frame_num = %d\n", read->iter.frame_num );
-	printf( "   x_offset = %d\n", read->iter.x_offset );
+	printf( "   left = %d\n", area.left );
-	printf( "   y_offset = %d\n", read->iter.y_offset );
+	printf( "   top = %d\n", area.top );
-	printf( "   width = %d\n", read->iter.width );
+	printf( "   width = %d\n", area.width );
-	printf( "   height = %d\n", read->iter.height );
+	printf( "   height = %d\n", area.height );
 	printf( "   duration = %d\n", read->iter.duration );
 	printf( "   dispose = " ); 
 	if( read->iter.dispose_method == WEBP_MUX_DISPOSE_BACKGROUND )
@@ -637,14 +693,14 @@ read_next_frame( Read *read )
 			"not all frames have equal duration" );
 
 	if( !(frame = read_frame( read, 
-		read->iter.width, read->iter.height, 
+		area.width, area.height,
 		read->iter.fragment.bytes, read->iter.fragment.size )) ) 
 		return( -1 );
 
 	/* Now blend or copy the new pixels into our accumulator.
 	 */
 	vips_image_paint_image( read->frame, frame, 
-		read->iter.x_offset, read->iter.y_offset, 
+		area.left, area.top, 
 		read->iter.blend_method == WEBP_MUX_BLEND );
 
 	g_object_unref( frame );
@@ -715,11 +771,11 @@ read_image( Read *read, VipsImage *out )
 
 int
 vips__webp_read_file( const char *filename, VipsImage *out, 
-	int page, int n, int shrink )
+	int page, int n, double scale )
 {
 	Read *read;
 
-	if( !(read = read_new( filename, NULL, 0, page, n, shrink )) ) {
+	if( !(read = read_new( filename, NULL, 0, page, n, scale )) ) {
 		vips_error( "webp2vips",
 			_( "unable to open \"%s\"" ), filename ); 
 		return( -1 );
@@ -737,11 +793,11 @@ vips__webp_read_file( const char *filename, VipsImage *out,
 
 int
 vips__webp_read_buffer_header( const void *buf, size_t len, VipsImage *out,
-	int page, int n, int shrink )
+	int page, int n, double scale )
 {
 	Read *read;
 
-	if( !(read = read_new( NULL, buf, len, page, n, shrink )) ) {
+	if( !(read = read_new( NULL, buf, len, page, n, scale )) ) {
 		vips_error( "webp2vips",
 			"%s", _( "unable to open buffer" ) ); 
 		return( -1 );
@@ -759,11 +815,11 @@ vips__webp_read_buffer_header( const void *buf, size_t len, VipsImage *out,
 
 int
 vips__webp_read_buffer( const void *buf, size_t len, VipsImage *out, 
-	int page, int n, int shrink )
+	int page, int n, double scale )
 {
 	Read *read;
 
-	if( !(read = read_new( NULL, buf, len, page, n, shrink )) ) {
+	if( !(read = read_new( NULL, buf, len, page, n, scale )) ) {
 		vips_error( "webp2vips",
 			"%s", _( "unable to open buffer" ) ); 
 		return( -1 );

libvips/foreign/webpload.c

@@ -6,6 +6,8 @@
  * 	- add @shrink
  * 1/11/18
  * 	- add @page, @n
+ * 30/4/19
+ * 	- deprecate @shrink, use @scale instead
  */
 
 /*
@@ -64,7 +66,11 @@ typedef struct _VipsForeignLoadWebp {
 	 */
 	int n;
 
-	/* Shrink by this much during load.
+	/* Scale by this much during load.
+	 */
+	double scale; 
+
+	/* Old and deprecated scaling path.
 	 */
 	int shrink;
 } VipsForeignLoadWebp;
@@ -120,10 +126,20 @@ vips_foreign_load_webp_class_init( VipsForeignLoadWebpClass *class )
 		G_STRUCT_OFFSET( VipsForeignLoadWebp, n ),
 		-1, 100000, 1 );
 
-	VIPS_ARG_INT( class, "shrink", 22, 
+	VIPS_ARG_DOUBLE( class, "scale", 22, 
+		_( "Scale" ), 
+		_( "Scale factor on load" ),
+		VIPS_ARGUMENT_OPTIONAL_INPUT,
+		G_STRUCT_OFFSET( VipsForeignLoadWebp, scale ),
+		0.0, 1024.0, 1.0 );
+
+	/* Old and deprecated scaling API. A float param lets do
+	 * shrink-on-load for thumbnail faster and more accurately.
+	 */
+	VIPS_ARG_INT( class, "shrink", 23, 
 		_( "Shrink" ), 
 		_( "Shrink factor on load" ),
-		VIPS_ARGUMENT_OPTIONAL_INPUT,
+		VIPS_ARGUMENT_OPTIONAL_INPUT | VIPS_ARGUMENT_DEPRECATED,
 		G_STRUCT_OFFSET( VipsForeignLoadWebp, shrink ),
 		1, 1024, 1 );
 
@@ -134,6 +150,7 @@ vips_foreign_load_webp_init( VipsForeignLoadWebp *webp )
 {
 	webp->n = 1;
 	webp->shrink = 1;
+	webp->scale = 1.0;
 }
 
 typedef struct _VipsForeignLoadWebpFile {
@@ -168,8 +185,15 @@ vips_foreign_load_webp_file_header( VipsForeignLoad *load )
 	VipsForeignLoadWebp *webp = (VipsForeignLoadWebp *) load;
 	VipsForeignLoadWebpFile *file = (VipsForeignLoadWebpFile *) load;
 
+	/* BC for the old API.
+	 */
+	if( !vips_object_argument_isset( VIPS_OBJECT( load ), "scale" ) &&
+		vips_object_argument_isset( VIPS_OBJECT( load ), "shrink" ) &&
+		webp->shrink != 0 )
+		webp->scale = 1.0 / webp->shrink;
+
 	if( vips__webp_read_file_header( file->filename, load->out, 
-		webp->page, webp->n, webp->shrink ) )
+		webp->page, webp->n, webp->scale ) )
 		return( -1 );
 
 	VIPS_SETSTR( load->out->filename, file->filename );
@@ -184,7 +208,7 @@ vips_foreign_load_webp_file_load( VipsForeignLoad *load )
 	VipsForeignLoadWebpFile *file = (VipsForeignLoadWebpFile *) load;
 
 	if( vips__webp_read_file( file->filename, load->real, 
-		webp->page, webp->n, webp->shrink ) )
+		webp->page, webp->n, webp->scale ) )
 		return( -1 );
 
 	return( 0 );
@@ -249,7 +273,7 @@ vips_foreign_load_webp_buffer_header( VipsForeignLoad *load )
 
 	if( vips__webp_read_buffer_header( buffer->buf->data, 
 		buffer->buf->length, load->out, 
-		webp->page, webp->n, webp->shrink ) )
+		webp->page, webp->n, webp->scale ) )
 		return( -1 );
 
 	return( 0 );
@@ -263,7 +287,7 @@ vips_foreign_load_webp_buffer_load( VipsForeignLoad *load )
 
 	if( vips__webp_read_buffer( buffer->buf->data, buffer->buf->length, 
 		load->real, 
-		webp->page, webp->n, webp->shrink ) )
+		webp->page, webp->n, webp->scale ) )
 		return( -1 );
 
 	return( 0 );
@@ -317,7 +341,7 @@ vips_foreign_load_webp_buffer_init( VipsForeignLoadWebpBuffer *buffer )
  *
  * * @page: %gint, page (frame) to read
  * * @n: %gint, load this many pages
- * * @shrink: %gint, shrink by this much on load
+ * * @scale: %gdouble, scale by this much on load
  *
  * Read a WebP file into a VIPS image. 
  *
@@ -328,7 +352,8 @@ vips_foreign_load_webp_buffer_init( VipsForeignLoadWebpBuffer *buffer )
  * left. Set to -1 to mean "until the end of the document". Use vips_grid() 
  * to change page layout.
  *
- * Use @shrink to specify a shrink-on-load factor.
+ * Use @scale to specify a scale-on-load factor. For example, 2.0 to double
+ * the size on load.
  *
  * The loader supports ICC, EXIF and XMP metadata. 
  *
@@ -360,7 +385,7 @@ vips_webpload( const char *filename, VipsImage **out, ... )
  *
  * * @page: %gint, page (frame) to read
  * * @n: %gint, load this many pages
- * * @shrink: %gint, shrink by this much on load
+ * * @scale: %gdouble, scale by this much on load
  *
  * Read a WebP-formatted memory block into a VIPS image. Exactly as
  * vips_webpload(), but read from a memory buffer. 

libvips/iofuncs/generate.c

@@ -635,7 +635,7 @@ write_vips( VipsRegion *region, VipsRect *area, void *a, void *b )
 	size_t nwritten, count;
 	void *buf;
 
-	count = region->bpl * area->height;
+	count = (size_t) region->bpl * area->height;
 	buf = VIPS_REGION_ADDR( region, 0, area->top );
 
 	do {

libvips/resample/thumbnail.c

@@ -109,17 +109,16 @@ typedef struct _VipsThumbnail {
 	int input_height;
 	int page_height;
 	VipsAngle angle; 		/* From vips_autorot_get_angle() */
+	int n_pages;			/* Pages in this image, not original */
 
 	/* For openslide, we need to read out the size of each level too.
+	 *
+	 * These are filled out for pyr tiffs as well.
 	 */
 	int level_count;
 	int level_width[MAX_LEVELS];
 	int level_height[MAX_LEVELS];
 
-	/* Try to get n-pages too, for pyr tiff load.
-	 */
-	int n_pages;
-
 	/* For HEIF, try to fetch the size of the stored thumbnail.
 	 */
 	int heif_thumbnail_width;
@@ -191,14 +190,16 @@ vips_thumbnail_read_header( VipsThumbnail *thumbnail, VipsImage *image )
 	thumbnail->input_width = image->Xsize;
 	thumbnail->input_height = image->Ysize;
 	thumbnail->angle = vips_autorot_get_angle( image );
+	thumbnail->page_height = vips_image_get_page_height( image );
 
-	if( vips_image_get_typeof( image, VIPS_META_N_PAGES ) ) {
+	/* The "n-pages" metadata item is the number of pages in the document, 
-		int n_pages;
+	 * not the number we've read out into this image. We calculate
-
+	 * ourselves from page_height. 
-		if( !vips_image_get_int( image, VIPS_META_N_PAGES, &n_pages ) ) 
+	 *
-			thumbnail->n_pages = 
+	 * vips_image_get_page_height() verifies that Ysize is a simple
-				VIPS_CLIP( 1, n_pages, MAX_LEVELS );
+	 * multiple of page_height.
-	}
+	 */
+	thumbnail->n_pages = thumbnail->input_height / thumbnail->page_height;
 
 	/* For openslide, read out the level structure too.
 	 */
@@ -226,6 +227,7 @@ vips_thumbnail_read_header( VipsThumbnail *thumbnail, VipsImage *image )
 }
 
 /* This may not be a pyr tiff, so no error if we can't find the layers. 
+ * We just look for two or more pages following roughly /2 shrinks.
  */
 static void
 vips_thumbnail_get_tiff_pyramid( VipsThumbnail *thumbnail ) 
@@ -233,6 +235,11 @@ vips_thumbnail_get_tiff_pyramid( VipsThumbnail *thumbnail )
 	VipsThumbnailClass *class = VIPS_THUMBNAIL_GET_CLASS( thumbnail );
 	int i;
 
+	/* Only one page? Can't be.
+	 */
+	if( thumbnail->n_pages < 2 )
+		return;
+
 	for( i = 0; i < thumbnail->n_pages; i++ ) {
 		VipsImage *page;
 		int level_width;
@@ -246,13 +253,10 @@ vips_thumbnail_get_tiff_pyramid( VipsThumbnail *thumbnail )
 		level_height = page->Ysize;
 		VIPS_UNREF( page );
 
-		/* Try to sanity-check the size of the pages. Do they look 
-		 * like a pyramid?
-		 */
 		expected_level_width = thumbnail->input_width / (1 << i);
 		expected_level_height = thumbnail->input_height / (1 << i);
 
-		/* Won't be exact due to rounding etc.
+		/* This won't be exact due to rounding etc.
 		 */
 		if( abs( level_width - expected_level_width ) > 5 ||
 			level_width < 2 )
@@ -405,7 +409,7 @@ vips_thumbnail_find_jpegshrink( VipsThumbnail *thumbnail,
 		return( 1 );
 }
 
-/* Find the best openslide level.
+/* Find the best pyramid (openslide or tiff) level.
  */
 static int
 vips_thumbnail_find_pyrlevel( VipsThumbnail *thumbnail, 
@@ -444,7 +448,7 @@ vips_thumbnail_open( VipsThumbnail *thumbnail )
 	g_info( "input size is %d x %d", 
 		thumbnail->input_width, thumbnail->input_height ); 
 
-	/* For tiff, we need to make a separate get_info() for each page to
+	/* For tiff, we need a separate ->open() for each page to
 	 * get all the pyramid levels.
 	 */
 	if( vips_isprefix( "VipsForeignLoadTiff", thumbnail->loader ) ) 
@@ -456,6 +460,10 @@ vips_thumbnail_open( VipsThumbnail *thumbnail )
 	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 ) ) {
@@ -465,20 +473,28 @@ vips_thumbnail_open( VipsThumbnail *thumbnail )
 		g_info( "loading jpeg with factor %g pre-shrink", factor ); 
 	}
 	else if( vips_isprefix( "VipsForeignLoadTiff", thumbnail->loader ) ||
-		vips_isprefix( "VipsForeignLoadOpenslide", thumbnail->loader ) ) {
+		vips_isprefix( "VipsForeignLoadOpenslide", 
+		thumbnail->loader ) ) {
 		factor = vips_thumbnail_find_pyrlevel( thumbnail, 
 			thumbnail->input_width, thumbnail->input_height );
 
 		g_info( "loading pyr level %g", factor ); 
 	}
-	else if( vips_isprefix( "VipsForeignLoadPdf", thumbnail->loader ) ||
+	else if( vips_isprefix( "VipsForeignLoadPdf", thumbnail->loader ) ) {
-		vips_isprefix( "VipsForeignLoadSvg", thumbnail->loader ) ) {
+		factor = 1.0 / 
+			vips_thumbnail_calculate_common_shrink( thumbnail, 
+				thumbnail->input_width, 
+				thumbnail->page_height );
+
+		g_info( "loading PDF with factor %g pre-scale", factor ); 
+	}
+	else if( vips_isprefix( "VipsForeignLoadSvg", thumbnail->loader ) ) {
 		factor = 1.0 / 
 			vips_thumbnail_calculate_common_shrink( thumbnail, 
 				thumbnail->input_width, 
 				thumbnail->input_height );
 
-		g_info( "loading PDF/SVG with factor %g pre-scale", factor ); 
+		g_info( "loading SVG with factor %g pre-scale", factor ); 
 	}
 	else if( vips_isprefix( "VipsForeignLoadHeif", thumbnail->loader ) ) {
 		/* 'factor' is a gboolean which enables thumbnail load instead
@@ -493,24 +509,14 @@ vips_thumbnail_open( VipsThumbnail *thumbnail )
 			factor = 0.0;
 
 	}
-
-	/* Webp supports shrink-on-load, but unfortunately the filter is just 
-	 * too odd. 
-	 *
-	 * Perhaps reenable this if webp improves.
-	 *
-	 * vips_thumbnail_file_open() and vips_thumbnail_buffer_open() would
-	 * need additional cases as well.
-	 *
 	else if( vips_isprefix( "VipsForeignLoadWebp", thumbnail->loader ) ) {
-		factor = VIPS_MAX( 1.0, 
+		factor = 1.0 /
 			vips_thumbnail_calculate_common_shrink( thumbnail, 
 				thumbnail->input_width, 
-				thumbnail->input_height ) ); 
+				thumbnail->page_height ); 
 
-		g_info( "loading webp with factor %g pre-shrink", factor ); 
+		g_info( "loading webp with factor %g pre-scale", factor ); 
 	}
-	 */
 
 	if( !(im = class->open( thumbnail, factor )) )
 		return( NULL );
@@ -529,6 +535,8 @@ vips_thumbnail_build( VipsObject *object )
 		VIPS_INTERPRETATION_scRGB : VIPS_INTERPRETATION_sRGB; 
 
 	VipsImage *in;
+	int preshrunk_page_height;
+	int output_page_height;
 	double hshrink;
 	double vshrink;
 
@@ -569,10 +577,9 @@ vips_thumbnail_build( VipsObject *object )
 		return( -1 );
 	in = t[0];
 
-	/* So page_height is after pre-shrink, but before the main shrink
+	/* After pre-shrink, but before the main shrink stage.
-	 * stage.
 	 */
-	thumbnail->page_height = vips_image_get_page_height( in );
+	preshrunk_page_height = vips_image_get_page_height( in );
 
 	/* RAD needs special unpacking.
 	 */
@@ -653,17 +660,17 @@ vips_thumbnail_build( VipsObject *object )
 		in = t[3];
 	}
 
-	/* Shrink to page_height, so we work for multi-page images.
+	/* Shrink to preshrunk_page_height, so we work for multi-page images.
 	 */
 	vips_thumbnail_calculate_shrink( thumbnail, 
-		in->Xsize, thumbnail->page_height, &hshrink, &vshrink );
+		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 pixel boundaries.
+	 * page_height or we'll have pixels straddling page boundaries.
 	 */
-	if( in->Ysize > thumbnail->page_height ) {
+	if( in->Ysize > preshrunk_page_height ) {
 		int target_page_height = VIPS_RINT( 
-			thumbnail->page_height / vshrink );
+			preshrunk_page_height / vshrink );
 		int target_image_height = target_page_height * 
 			thumbnail->n_pages;
 
@@ -676,8 +683,9 @@ vips_thumbnail_build( VipsObject *object )
 		return( -1 );
 	in = t[4];
 
-	thumbnail->page_height = VIPS_RINT( thumbnail->page_height / vshrink );
+	output_page_height = VIPS_RINT( preshrunk_page_height / vshrink );
-	vips_image_set_int( in, VIPS_META_PAGE_HEIGHT, thumbnail->page_height );
+	vips_image_set_int( in, 
+		VIPS_META_PAGE_HEIGHT, output_page_height );
 
 	if( have_premultiplied ) {
 		g_info( "unpremultiplying alpha" ); 
@@ -942,7 +950,8 @@ vips_thumbnail_file_open( VipsThumbnail *thumbnail, double factor )
 			NULL ) );
 	}
 	else if( vips_isprefix( "VipsForeignLoadPdf", thumbnail->loader ) ||
-		vips_isprefix( "VipsForeignLoadSvg", thumbnail->loader ) ) {
+		vips_isprefix( "VipsForeignLoadSvg", thumbnail->loader ) ||
+		vips_isprefix( "VipsForeignLoadWebp", thumbnail->loader ) ) {
 		return( vips_image_new_from_file( file->filename, 
 			"access", VIPS_ACCESS_SEQUENTIAL,
 			"scale", factor,
@@ -1137,7 +1146,8 @@ vips_thumbnail_buffer_open( VipsThumbnail *thumbnail, double factor )
 			NULL ) );
 	}
 	else if( vips_isprefix( "VipsForeignLoadPdf", thumbnail->loader ) ||
-		vips_isprefix( "VipsForeignLoadSvg", 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,

test/test-suite/test_foreign.py

@@ -597,7 +597,7 @@ class TestForeign:
         def pdf_valid(im):
             a = im(10, 10)
             assert_almost_equal_objects(a, [35, 31, 32, 255])
-            assert im.width == 1133
+            assert im.width == 1134
             assert im.height == 680
             assert im.bands == 4