Merge branch 'loader-minimise-experiment'

ChangeLog

@@ -6,6 +6,7 @@
 - disable webp alpha output if all frames fill the canvas and are solid
 - add "compression" option to heifsave [lovell]
 - support webp and zstd compression in tiff
+- loaders use "minimise" to close input files earlier
 - integrate support for oss-fuzz [omira-sch]
 
 9/7/19 started 8.8.2

cplusplus/examples/test_overloads.cpp

@@ -34,7 +34,8 @@ equal_vector( std::vector<double> a, std::vector<double> b )
 				printf( "%g", a[i] );
 			}
 			printf( "], is [" );
-			for( unsigned int i = 0; i < a.size(); i++ ) { if( i > 0 )
+			for( unsigned int i = 0; i < a.size(); i++ ) { 
+				if( i > 0 )
 					printf( ", " ); 
 				printf( "%g", a[i] );
 			}

libvips/conversion/insert.c

@@ -103,6 +103,10 @@ typedef struct _VipsInsert {
 	VipsRect rout;		/* Output space */
 	VipsRect rmain;		/* Position of main in output */
 	VipsRect rsub;		/* Position of sub in output */
+
+	/* TRUE if we've minimise sub.
+	 */
+	gboolean sub_minimised;
 } VipsInsert;
 
 typedef VipsConversionClass VipsInsertClass;
@@ -164,8 +168,6 @@ vips__insert_paste_region( VipsRegion *or, VipsRegion *ir, VipsRect *pos )
 	return( 0 );
 }
 
-/* Insert generate function.
- */
 static int
 vips_insert_gen( VipsRegion *or, void *seq, void *a, void *b, gboolean *stop )
 {
@@ -175,39 +177,43 @@ vips_insert_gen( VipsRegion *or, void *seq, void *a, void *b, gboolean *stop )
 
 	VipsRect ovl;
 
-	/* Does the rect we have been asked for fall entirely inside the
+	/* The part of the subimage we will use.
-	 * sub-image?
-	 */
-	if( vips_rect_includesrect( &insert->rsub, &or->valid ) ) 
-		return( vips__insert_just_one( or, ir[1], 
-			insert->rsub.left, insert->rsub.top ) );
-
-	/* Does it fall entirely inside the main, and not at all inside the
-	 * sub?
 	 */
 	vips_rect_intersectrect( &or->valid, &insert->rsub, &ovl );
-	if( vips_rect_includesrect( &insert->rmain, &or->valid ) &&
-		vips_rect_isempty( &ovl ) ) 
-		return( vips__insert_just_one( or, ir[0], 
-			insert->rmain.left, insert->rmain.top ) );
 
-	/* Output requires both (or neither) input. If it is not entirely 
+	/* Three cases: we are generating entirely within the sub-image, 
-	 * inside both the main and the sub, then there is going to be some
+	 * entirely within the main image, or a mixture.
-	 * background. 
 	 */
-	if( !(vips_rect_includesrect( &insert->rsub, &or->valid ) &&
+	if( vips_rect_includesrect( &insert->rsub, &or->valid ) ) {
-		vips_rect_includesrect( &insert->rmain, &or->valid )) )
+		if( vips__insert_just_one( or, ir[1], 
-		vips_region_paint_pel( or, r, insert->ink );
+			insert->rsub.left, insert->rsub.top ) )
+			return( -1 );
+	}
+	else if( vips_rect_includesrect( &insert->rmain, &or->valid ) &&
+		vips_rect_isempty( &ovl ) ) {
+		if( vips__insert_just_one( or, ir[0], 
+			insert->rmain.left, insert->rmain.top ) )
+			return( -1 );
+	}
+	else {
+		/* Output requires both (or neither) input. If it is not 
+		 * entirely inside both the main and the sub, then there is 
+		 * going to be some background. 
+		 */
+		if( !(vips_rect_includesrect( &insert->rsub, &or->valid ) &&
+			vips_rect_includesrect( &insert->rmain, &or->valid )) )
+			vips_region_paint_pel( or, r, insert->ink );
 
-	/* Paste from main.
+		/* Paste from main.
-	 */
+		 */
-	if( vips__insert_paste_region( or, ir[0], &insert->rmain ) )
+		if( vips__insert_paste_region( or, ir[0], &insert->rmain ) )
-		return( -1 );
+			return( -1 );
 
-	/* Paste from sub.
+		/* Paste from sub.
-	 */
+		 */
-	if( vips__insert_paste_region( or, ir[1], &insert->rsub ) )
+		if( vips__insert_paste_region( or, ir[1], &insert->rsub ) )
-		return( -1 );
+			return( -1 );
+	}
 
 	return( 0 );
 }

libvips/foreign/foreign.c

@@ -838,7 +838,7 @@ vips_foreign_load_start( VipsImage *out, void *a, void *b )
 
 		/* Load the image and check the result.
 		 *
-		 * ->header() read the header into @out, load has read the
+		 * ->header() read the header into @out, load will read the
 		 * image into @real. They must match exactly in size, bands,
 		 * format and coding for the copy to work.  
 		 *

libvips/foreign/gifload.c

@@ -24,6 +24,9 @@
  * 	- rework as a sequential loader ... simpler, much lower mem use
  * 6/7/19 [deftomat]
  * 	- support array of delays 
+ * 24/7/19
+ * 	- close early on minimise 
+ * 	- close early on error
  */
 
 /*
@@ -637,8 +640,6 @@ vips_foreign_load_gif_header( VipsForeignLoad *load )
 				return( -1 );
 			}
 
-			/* Read in the image record.
-			 */
 			if( vips_foreign_load_gif_scan_image_record( gif ) )
 				return( -1 );
 
@@ -647,7 +648,7 @@ vips_foreign_load_gif_header( VipsForeignLoad *load )
 			break;
 
 		case EXTENSION_RECORD_TYPE:
-			/* We will need to fetch the extensions to check for
+			/* We need to fetch the extensions to check for
 			 * cmaps and transparency.
 			 */
 			if( vips_foreign_load_gif_scan_extension( gif ) )
@@ -1009,6 +1010,12 @@ vips_foreign_load_gif_generate( VipsRegion *or,
 	return( 0 );
 }
 
+static void
+vips_foreign_load_gif_minimise( VipsObject *object, VipsForeignLoadGif *gif )
+{
+	vips_foreign_load_gif_close( gif );
+}
+
 static int
 vips_foreign_load_gif_load( VipsForeignLoad *load )
 {
@@ -1052,6 +1059,11 @@ vips_foreign_load_gif_load( VipsForeignLoad *load )
 	if( vips_foreign_load_gif_set_header( gif, t[0] ) )
 		return( -1 );
 
+	/* Close input immediately at end of read.
+	 */
+	g_signal_connect( t[0], "minimise", 
+		G_CALLBACK( vips_foreign_load_gif_minimise ), gif ); 
+
 	/* Strips 8 pixels high to avoid too many tiny regions.
 	 */
 	if( vips_image_generate( t[0],
@@ -1189,6 +1201,26 @@ vips_giflib_file_read( GifFileType *file, GifByteType *buffer, int n )
 	return( (int) fread( (void *) buffer, 1, n, fp ) );
 }
 
+static int
+vips_foreign_load_gif_file_header( VipsForeignLoad *load )
+{
+	VipsForeignLoadGifFile *file = (VipsForeignLoadGifFile *) load;
+
+	if( VIPS_FOREIGN_LOAD_CLASS( 
+		vips_foreign_load_gif_file_parent_class )->header( load ) ) {
+		/* Close early if header read fails in our base class.
+		 */
+		VIPS_FREEF( fclose, file->fp );
+		return( -1 );
+	}
+
+	return( 0 );
+}
+
+/* We have to have _open() as a vfunc since our base class needs to be able to
+ * make two scans of the gif (scan for header, then scan for pixels), so we 
+ * must be able to close and reopen (or rewind).
+ */
 static int
 vips_foreign_load_gif_file_open( VipsForeignLoadGif *gif )
 {
@@ -1238,6 +1270,7 @@ vips_foreign_load_gif_file_class_init(
 	foreign_class->suffs = vips_foreign_gif_suffs;
 
 	load_class->is_a = vips_foreign_load_gif_is_a;
+	load_class->header = vips_foreign_load_gif_file_header;
 
 	gif_class->open = vips_foreign_load_gif_file_open;
 

libvips/foreign/heifload.c

@@ -4,6 +4,9 @@
  * 	- from niftiload.c
  * 24/7/19 [zhoux2016]
  * 	- always fetch metadata from the main image (thumbs don't have it)
+ * 24/7/19
+ * 	- close early on minimise 
+ * 	- close early on error
  */
 
 /*
@@ -130,14 +133,21 @@ typedef VipsForeignLoadClass VipsForeignLoadHeifClass;
 G_DEFINE_ABSTRACT_TYPE( VipsForeignLoadHeif, vips_foreign_load_heif, 
 	VIPS_TYPE_FOREIGN_LOAD );
 
+static void
+vips_foreign_load_heif_close( VipsForeignLoadHeif *heif )
+{
+	VIPS_FREEF( heif_image_release, heif->img );
+	heif->data = NULL;
+	VIPS_FREEF( heif_image_handle_release, heif->handle );
+	VIPS_FREEF( heif_context_free, heif->ctx );
+}
+
 static void
 vips_foreign_load_heif_dispose( GObject *gobject )
 {
 	VipsForeignLoadHeif *heif = (VipsForeignLoadHeif *) gobject;
 
-	VIPS_FREEF( heif_image_release, heif->img );
+	vips_foreign_load_heif_close( heif );
-	VIPS_FREEF( heif_image_handle_release, heif->handle );
-	VIPS_FREEF( heif_context_free, heif->ctx );
 	VIPS_FREE( heif->id );
 
 	G_OBJECT_CLASS( vips_foreign_load_heif_parent_class )->
@@ -707,6 +717,12 @@ vips_foreign_load_heif_generate( VipsRegion *or,
 	return( 0 );
 }
 
+static void
+vips_foreign_load_heif_minimise( VipsObject *object, VipsForeignLoadHeif *heif )
+{
+	vips_foreign_load_heif_close( heif );
+}
+
 static int
 vips_foreign_load_heif_load( VipsForeignLoad *load )
 {
@@ -722,6 +738,12 @@ vips_foreign_load_heif_load( VipsForeignLoad *load )
 	t[0] = vips_image_new();
 	if( vips_foreign_load_heif_set_header( heif, t[0] ) )
 		return( -1 );
+
+	/* CLose input immediately at end of read.
+	 */
+	g_signal_connect( t[0], "minimise", 
+		G_CALLBACK( vips_foreign_load_heif_minimise ), heif ); 
+
 	if( vips_image_generate( t[0],
 		NULL, vips_foreign_load_heif_generate, NULL, heif, NULL ) ||
 		vips_sequential( t[0], &t[1], NULL ) ||
@@ -821,13 +843,20 @@ vips_foreign_load_heif_file_header( VipsForeignLoad *load )
 
 	error = heif_context_read_from_file( heif->ctx, file->filename, NULL );
 	if( error.code ) {
+		/* Make we close the fd as soon as we can on error.
+		 */
+		vips_foreign_load_heif_close( heif ); 
 		vips__heif_error( &error );
 		return( -1 );
 	}
 
 	if( VIPS_FOREIGN_LOAD_CLASS( 
-		vips_foreign_load_heif_file_parent_class )->header( load ) )
+		vips_foreign_load_heif_file_parent_class )->header( load ) ) {
+		/* Close early if our base class fails to read.
+		 */
+		vips_foreign_load_heif_close( heif ); 
 		return( -1 );
+	}
 
 	VIPS_SETSTR( load->out->filename, file->filename );
 

libvips/foreign/jpeg2vips.c

@@ -100,6 +100,8 @@
  * 	- strict round down on shrink-on-load
  * 16/8/18
  * 	- shut down the input file as soon as we can [kleisauke]
+ * 20/7/19
+ * 	- close input on minimise rather than Y read position
  */
 
 /*
@@ -190,8 +192,7 @@ typedef struct _ReadJpeg {
 	int output_height;
 } ReadJpeg;
 
-/* This can be called many times. It's called directly at the end of image
+/* This can be called many times. 
- * read.
  */
 static void
 readjpeg_close_input( ReadJpeg *jpeg )
@@ -237,6 +238,12 @@ readjpeg_close_cb( VipsObject *object, ReadJpeg *jpeg )
 	(void) readjpeg_free( jpeg );
 }
 
+static void
+readjpeg_minimise_cb( VipsObject *object, ReadJpeg *jpeg )
+{
+	readjpeg_close_input( jpeg );
+}
+
 static ReadJpeg *
 readjpeg_new( VipsImage *out, int shrink, gboolean fail, gboolean autorotate )
 {
@@ -270,6 +277,8 @@ readjpeg_new( VipsImage *out, int shrink, gboolean fail, gboolean autorotate )
 
 	g_signal_connect( out, "close", 
 		G_CALLBACK( readjpeg_close_cb ), jpeg ); 
+	g_signal_connect( out, "minimise", 
+		G_CALLBACK( readjpeg_minimise_cb ), jpeg ); 
 
 	return( jpeg );
 }
@@ -290,20 +299,17 @@ readjpeg_file( ReadJpeg *jpeg, const char *filename )
 static const char *
 find_chroma_subsample( struct jpeg_decompress_struct *cinfo )
 {
-	gboolean has_subsample;
-
 	/* libjpeg only uses 4:4:4 and 4:2:0, confusingly. 
 	 *
 	 * http://poynton.ca/PDFs/Chroma_subsampling_notation.pdf
 	 */
-	has_subsample = cinfo->max_h_samp_factor > 1 ||
+	gboolean has_subsample = cinfo->max_h_samp_factor > 1 ||
 		cinfo->max_v_samp_factor > 1;
-	if( cinfo->num_components > 3 )
+	gboolean is_cmyk = cinfo->num_components > 3;
-		/* A cmyk image.
+
-		 */
+	return( is_cmyk ? 
-		return( has_subsample ? "4:2:0:4" : "4:4:4:4" );
+		(has_subsample ? "4:2:0:4" : "4:4:4:4" ) :
-	else
+		(has_subsample ? "4:2:0" : "4:4:4") );
-		return( has_subsample ? "4:2:0" : "4:4:4" );
 }
 
 static int
@@ -718,7 +724,7 @@ read_jpeg_generate( VipsRegion *or,
 		jpeg->y_pos += 1; 
 	}
 
-	/* Shut down the input file as soon as we can. 
+	/* Shut down the input early if we can.
 	 */
 	if( jpeg->y_pos >= or->im->Ysize ) 
 		readjpeg_close_input( jpeg );

libvips/foreign/openexr2vips.c

@@ -348,11 +348,6 @@ vips__openexr_generate( VipsRegion *out,
 			}
 		}
 
-	/* We can't shut down the input file early for tile read, even if we
-	 * know load is in sequential mode, since we are not inside a
-	 * vips_sequential() and requests are not guaranteed to be in order.
-	 */
-
 	return( 0 );
 }
 

libvips/foreign/pdfiumload.c

@@ -380,6 +380,15 @@ vips_foreign_load_pdf_header( VipsForeignLoad *load )
 	return( 0 );
 }
 
+static void
+vips_foreign_load_pdf_minimise( VipsObject *object, VipsForeignLoadPdf *pdf )
+{
+	/* In seq mode, we can shut down the input at the end of computation.
+	 */
+	if( VIPS_FOREIGN_LOAD( pdf )->access == VIPS_ACCESS_SEQUENTIAL )
+		vips_foreign_load_pdf_close( pdf ); 
+}
+
 static int
 vips_foreign_load_pdf_generate( VipsRegion *or, 
 	void *seq, void *a, void *b, gboolean *stop )
@@ -436,13 +445,6 @@ vips_foreign_load_pdf_generate( VipsRegion *or,
 		i += 1;
 	}
 
-	/* In seq mode, we can shut down the input when we render the last
-	 * row.
-	 */
-	if( top >= or->im->Ysize &&
-		load->access == VIPS_ACCESS_SEQUENTIAL )
-		vips_foreign_load_pdf_close( pdf ); 
-
 	/* PDFium writes BRGA, we must swap.
 	 *
 	 * FIXME ... this is a bit slow.
@@ -476,6 +478,11 @@ vips_foreign_load_pdf_load( VipsForeignLoad *load )
 	 */
 	t[0] = vips_image_new(); 
 
+	/* Close input immediately at end of read.
+	 */
+	g_signal_connect( t[0], "minimise", 
+		G_CALLBACK( vips_foreign_load_pdf_minimise ), pdf ); 
+
 	vips_foreign_load_pdf_set_image( pdf, t[0] ); 
 	if( vips_image_generate( t[0], 
 		NULL, vips_foreign_load_pdf_generate, NULL, pdf, NULL ) )

libvips/foreign/pdfload.c

@@ -334,12 +334,20 @@ vips_foreign_load_pdf_header( VipsForeignLoad *load )
 	return( 0 );
 }
 
+static void
+vips_foreign_load_pdf_minimise( VipsObject *object, VipsForeignLoadPdf *pdf )
+{
+	/* In seq mode, we can shut down the input at the end of computation.
+	 */
+	if( VIPS_FOREIGN_LOAD( pdf )->access == VIPS_ACCESS_SEQUENTIAL )
+		vips_foreign_load_pdf_close( pdf ); 
+}
+
 static int
 vips_foreign_load_pdf_generate( VipsRegion *or, 
 	void *seq, void *a, void *b, gboolean *stop )
 {
 	VipsForeignLoadPdf *pdf = (VipsForeignLoadPdf *) a;
-	VipsForeignLoad *load = (VipsForeignLoad *) pdf;
 	VipsRect *r = &or->valid;
 
 	int top;
@@ -398,13 +406,6 @@ vips_foreign_load_pdf_generate( VipsRegion *or,
 		i += 1;
 	}
 
-	/* In seq mode, we can shut down the input when we render the last
-	 * row.
-	 */
-	if( top >= or->im->Ysize &&
-		load->access == VIPS_ACCESS_SEQUENTIAL )
-		vips_foreign_load_pdf_close( pdf ); 
-
 	/* Cairo makes pre-multipled BRGA, we must byteswap and unpremultiply.
 	 */
 	for( y = 0; y < r->height; y++ ) 
@@ -430,6 +431,11 @@ vips_foreign_load_pdf_load( VipsForeignLoad *load )
 	 */
 	t[0] = vips_image_new(); 
 
+	/* Close input immediately at end of read.
+	 */
+	g_signal_connect( t[0], "minimise", 
+		G_CALLBACK( vips_foreign_load_pdf_minimise ), pdf ); 
+
 	vips_foreign_load_pdf_set_image( pdf, t[0] ); 
 	if( vips_image_generate( t[0], 
 		NULL, vips_foreign_load_pdf_generate, NULL, pdf, NULL ) )

libvips/foreign/radiance.c

@@ -984,12 +984,17 @@ vips__rad_israd( const char *filename )
 	return( result == 1 );
 }
 
+static void
+read_minimise( VipsObject *object, Read *read )
+{
+	VIPS_FREEF( buffer_free, read->buffer );
+	VIPS_FREEF( fclose, read->fin );
+}
+
 static void
 read_destroy( VipsObject *object, Read *read )
 {
 	VIPS_FREE( read->filename );
-	VIPS_FREEF( fclose, read->fin );
-	VIPS_FREEF( buffer_free, read->buffer );
 }
 
 static Read *
@@ -1019,6 +1024,8 @@ read_new( const char *filename, VipsImage *out )
 	read->prims[3][1] = CIE_y_w;
 	read->buffer = NULL;
 
+	g_signal_connect( out, "minimise", 
+		G_CALLBACK( read_minimise ), read );
 	g_signal_connect( out, "close", 
 		G_CALLBACK( read_destroy ), read );
 

libvips/foreign/tiff2vips.c

@@ -189,6 +189,8 @@
  * 7/6/19
  * 	- istiff reads the first directory rather than just testing the magic
  * 	  number, so it ignores more TIFF-like, but not TIFF images
+ * 20/7/19
+ * 	- use "minimise" for early shutdown, rather than read Y position
  */
 
 /*
@@ -494,6 +496,20 @@ rtiff_close_cb( VipsObject *object, Rtiff *rtiff )
 	rtiff_free( rtiff ); 
 }
 
+static void
+rtiff_minimise_cb( VipsObject *object, Rtiff *rtiff )
+{
+#ifdef DEBUG
+	printf( "rtiff_minimise_cb: %p minimise\n", rtiff );
+#endif /*DEBUG*/
+
+	/* Close early for non-tiled TIFFs. Tiled TIFFs are read randomly, so
+	 * the end of a loop doesn't mean the tiff won't be used again.
+	 */
+	if( !rtiff->header.tiled )
+		rtiff_free( rtiff ); 
+}
+
 static Rtiff *
 rtiff_new( VipsImage *out, int page, int n, gboolean autorotate )
 {
@@ -520,6 +536,9 @@ rtiff_new( VipsImage *out, int page, int n, gboolean autorotate )
 	g_signal_connect( out, "close", 
 		G_CALLBACK( rtiff_close_cb ), rtiff ); 
 
+	g_signal_connect( out, "minimise", 
+		G_CALLBACK( rtiff_minimise_cb ), rtiff ); 
+
 	if( rtiff->page < 0 || rtiff->page > 1000000 ) {
 		vips_error( "tiff2vips", _( "bad page number %d" ),
 			rtiff->page );
@@ -1603,11 +1622,6 @@ rtiff_fill_region( VipsRegion *out,
 
 	VIPS_GATE_STOP( "rtiff_fill_region: work" ); 
 
-	/* We can't shut down the input file early for tile read, even if we
-	 * know load is in sequential mode, since we are not inside a
-	 * vips_sequential() and requests are not guaranteed to be in order.
-	 */
-
 	return( 0 );
 }
 
@@ -1949,11 +1963,11 @@ rtiff_stripwise_generate( VipsRegion *or,
 		rtiff->y_pos += hit.height;
 	}
 
-	/* Shut down the input file as soon as we can. 
+	/* Shut down the input file as soon as we can.
 	 */
 	if( rtiff->y_pos >= or->im->Ysize ) {
 #ifdef DEBUG
-		printf( "rtiff_stripwise_generate: early shutdown\n" ); 
+		printf( "rtiff_stripwise_generate: early shutdown\n" );
 #endif /*DEBUG*/
 		rtiff_free( rtiff );
 	}

libvips/foreign/vipspng.c

@@ -196,6 +196,22 @@ read_close_cb( VipsImage *out, Read *read )
 	read_destroy( read ); 
 }
 
+static void
+read_minimise_cb( VipsImage *out, Read *read )
+{
+	/* Catch errors from png_read_end(). This can fail on a truncated
+	 * file. 
+	 */
+	if( read->pPng ) {
+		/* Catch and ignore error returns from png_read_end().
+		 */
+		if( !setjmp( png_jmpbuf( read->pPng ) ) ) 
+			png_read_end( read->pPng, NULL ); 
+	}
+
+	read_destroy( read );
+}
+
 static Read *
 read_new( VipsImage *out, gboolean fail )
 {
@@ -218,6 +234,8 @@ read_new( VipsImage *out, gboolean fail )
 
 	g_signal_connect( out, "close", 
 		G_CALLBACK( read_close_cb ), read ); 
+	g_signal_connect( out, "minimise", 
+		G_CALLBACK( read_minimise_cb ), read ); 
 
 	if( !(read->pPng = png_create_read_struct( 
 		PNG_LIBPNG_VER_STRING, NULL,
@@ -643,22 +661,21 @@ png2vips_generate( VipsRegion *or,
 	}
 
 	/* Catch errors from png_read_end(). This can fail on a truncated
-	 * file. 
+	 * file.
 	 */
 	if( setjmp( png_jmpbuf( read->pPng ) ) ) {
 		if( read->fail ) {
-			vips_error( "vipspng", "%s", _( "libpng read error" ) ); 
+			vips_error( "vipspng", "%s", _( "libpng read error" ) );
 			return( -1 );
 		}
 
 		return( 0 );
 	}
 
-	/* We need to shut down the reader immediately at the end of read or
+	/* Early close to free the fd as soon as we can.
-	 * we won't detach ready for the next image.
 	 */
 	if( read->y_pos >= read->out->Ysize ) {
-		png_read_end( read->pPng, NULL ); 
+		png_read_end( read->pPng, NULL );
 		read_destroy( read );
 	}
 

libvips/foreign/webp2vips.c

@@ -342,8 +342,8 @@ vips__iswebp( const char *filename )
 	return( 0 );
 }
 
-static int
+static void
-read_free( Read *read )
+read_minimise( Read *read )
 {
 	WebPDemuxReleaseIterator( &read->iter );
 	VIPS_UNREF( read->frame );
@@ -359,6 +359,13 @@ read_free( Read *read )
 	}
 
 	VIPS_FREEF( vips_tracked_close, read->fd ); 
+}
+
+static int
+read_free( Read *read )
+{
+	read_minimise( read );
+
 	VIPS_FREE( read->filename );
 	VIPS_FREE( read->delays );
 	VIPS_FREE( read );
@@ -793,6 +800,12 @@ read_webp_generate( VipsRegion *or,
 	return( 0 );
 }
 
+static void
+read_minimise_cb( VipsObject *object, Read *read )
+{
+	read_minimise( read );
+}
+
 static int
 read_image( Read *read, VipsImage *out )
 {
@@ -803,6 +816,9 @@ read_image( Read *read, VipsImage *out )
 	if( read_header( read, t[0] ) )
 		return( -1 );
 
+	g_signal_connect( t[0], "minimise", 
+		G_CALLBACK( read_minimise_cb ), read );
+
 	if( vips_image_generate( t[0], 
 		NULL, read_webp_generate, NULL, read, NULL ) ||
 		vips_sequential( t[0], &t[1], NULL ) ||

libvips/include/vips/image.h

@@ -426,6 +426,8 @@ void vips_image_invalidate_all( VipsImage *image );
 
 void vips_image_minimise_all( VipsImage *image );
 
+gboolean vips_image_is_sequential( VipsImage *image );
+
 void vips_image_set_progress( VipsImage *image, gboolean progress );
 gboolean vips_image_iskilled( VipsImage *image );
 void vips_image_set_kill( VipsImage *image, gboolean kill );

libvips/iofuncs/image.c

@@ -451,11 +451,9 @@ vips_image_finalize( GObject *gobject )
 		VIPS_FREE( image->time );
 	}
 
-	/* Any image data?
+	/* Free attached memory.
 	 */
 	if( image->data ) {
-		/* Buffer image. Only free stuff we know we allocated.
-		 */
 		if( image->dtype == VIPS_IMAGE_SETBUF ) {
 			VIPS_DEBUG_MSG( "vips_image_finalize: "
 				"freeing buffer\n" );
@@ -466,7 +464,7 @@ vips_image_finalize( GObject *gobject )
 		image->data = NULL;
 	}
 
-	/* If this is a temp, delete it.
+	/* Delete associated files.
 	 */
 	vips_image_delete( image );
 
@@ -1454,6 +1452,22 @@ vips_image_minimise_all( VipsImage *image )
 		(VipsSListMap2Fn) vips_image_minimise_all_cb, NULL, NULL );
 }
 
+/**
+ * vips_image_is_sequential: (method)
+ * @image: #VipsImage to minimise
+ *
+ * TRUE if any of the images upstream from @image were opened in sequential
+ * mode. Some operations change behaviour slightly in sequential mode to
+ * optimise memory behaviour.
+ *
+ * Returns: %TRUE if @image is in sequential mode.
+ */
+gboolean
+vips_image_is_sequential( VipsImage *image )
+{
+	return( vips_image_get_typeof( image, VIPS_META_SEQUENTIAL ) );
+}
+
 /* Attach a new time struct, if necessary, and reset it.
  */
 static int
@@ -2066,9 +2080,8 @@ vips_image_new_from_memory_copy_cb( VipsImage *image, void *data_copy )
  * @format: image format
  *
  * Like vips_image_new_from_memory(), but VIPS will make a copy of the memory 
- * area. This
+ * area. This means more memory use and an extra copy operation, but is much 
- * means more memory use and an extra copy operation, but is much simpler and
+ * simpler and safer. 
- * safer. 
  *
  * See also: vips_image_new_from_memory().
  *

libvips/resample/shrinkv.c

@@ -45,8 +45,6 @@
  * 	- rename yshrink -> vshrink for greater consistency 
  * 7/3/17
  * 	- add a seq line cache
- * 9/7/19
- * 	- read the tail of the input to force early shutdown in seq readers
  */
 
 /*
@@ -101,7 +99,6 @@ typedef struct _VipsShrinkv {
 
 	int vshrink;
 	size_t sizeof_line_buffer;
-	gboolean sequential;
 
 } VipsShrinkv;
 
@@ -268,7 +265,6 @@ vips_shrinkv_gen( VipsRegion *or, void *vseq,
 {
 	VipsShrinkvSequence *seq = (VipsShrinkvSequence *) vseq;
 	VipsShrinkv *shrink = (VipsShrinkv *) b;
-	VipsResample *resample = VIPS_RESAMPLE( shrink );
 	VipsRegion *ir = seq->ir;
 	VipsRect *r = &or->valid;
 
@@ -319,38 +315,6 @@ vips_shrinkv_gen( VipsRegion *or, void *vseq,
 
 	VIPS_COUNT_PIXELS( or, "vips_shrinkv_gen" ); 
 
-	/* If we are in seq mode and we've just generated the last line of 
-	 * the output, make sure we read all of the input.
-	 *
-	 * This will trigger the early shutdown logic in things like the 
-	 * tiff loader.
-	 */
-	if( shrink->sequential &&
-		r->top + r->height >= or->im->Ysize ) {
-		/* First unused scanline. resample->in->Ysize because we want
-		 * the height before the embed.
-		 */
-		int first = or->im->Ysize * shrink->vshrink;
-		int unused = resample->in->Ysize - first;
-
-		g_assert( unused >= 0 );
-
-		for( y = 0; y < unused; y++ ) { 
-			VipsRect s;
-
-			s.left = r->left;
-			s.top = first + y;
-			s.width = r->width;
-			s.height = 1;
-#ifdef DEBUG
-			printf( "shrink_gen: requesting tail %d\n", s.top ); 
-#endif /*DEBUG*/
-
-			if( vips_region_prepare( ir, &s ) )
-				return( -1 );
-		}
-	}
-
 	return( 0 );
 }
 
@@ -448,11 +412,9 @@ vips_shrinkv_build( VipsObject *object )
 	 * always have the previous XX lines of the shrunk image, and we won't
 	 * fetch out of order. 
 	 */
-	if( vips_image_get_typeof( in, VIPS_META_SEQUENTIAL ) ) { 
+	if( vips_image_is_sequential( in ) ) { 
 		g_info( "shrinkv sequential line cache" ); 
 
-		shrink->sequential = TRUE;
-
 		if( vips_sequential( in, &t[3], 
 			"tile_height", 10,
 			NULL ) )