diff --git a/ChangeLog b/ChangeLog
index 7f672e02..91da761c 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -22,6 +22,7 @@
 - added vips_image_new_matrixv()
 - dzsave basename param now called filename, so you can use .dz as a
   destination (basename is still there but deprecated)
+- new _UNBUFFERED sequential mode saves memory in some important cases
 
 3/7/13 started 7.34.2
 - lower priority for Matlab load to reduce segvs from Mat_Open(), thanks
diff --git a/TODO b/TODO
index b1505ccd..4b00e424 100644
--- a/TODO
+++ b/TODO
@@ -1,49 +1,4 @@
 
-- need a new uncached mode for open via disc
-
-	currently we have a huge linecache for "vips copy x.png x.v", in
-	effect what vips does for open-via-disc, and therefore see >100mb ram
-	use even in open-via-disc mode
-
-	add SEQUENTIAL_UNBUFFERED?
-
-	could we spot from the demand style? they do almost the same thing,
-	though one is static and one dynamic, I guess
-
-
-  vips_object_set_argument_from_string() looks at the operation class and 
-  sets ("sequential", TRUE) for image arguments
-
-  the "seq" arg needs to be an enum with various settings
-
-  	"access", 
-		RANDOM, SEQUENTIAL, SEQUENTIAL_UNBUFFERED
-
-
-
-
-  todo:
-
-  add a new operation flag, try setting it on vips_copy(), pass the flag down
-  to "access"
-
-  in foreign/*.c, evey place that uses vips_sequential() needs to be passed a
-  copy of "access"
-
-  when it calls vips_sequential(), it needs to set an access hint
-
-  vips_sequential() needs to pass this down to vips_linecache()
-
-  vips_linecache_build() needs to use this to adjust the setting of
-  max_tiles
-
-
-
-
-
-
-
-
 - finish hist_ismonotonic()
 
 	needs im_conv()
diff --git a/libvips/arithmetic/arithmetic.c b/libvips/arithmetic/arithmetic.c
index 8dbdce7d..59fe05aa 100644
--- a/libvips/arithmetic/arithmetic.c
+++ b/libvips/arithmetic/arithmetic.c
@@ -577,7 +577,7 @@ vips_arithmetic_class_init( VipsArithmeticClass *class )
 	vobject_class->description = _( "arithmetic operations" );
 	vobject_class->build = vips_arithmetic_build;
 
-	operation_class->flags = VIPS_OPERATION_SEQUENTIAL;
+	operation_class->flags = VIPS_OPERATION_SEQUENTIAL_UNBUFFERED;
 
 	VIPS_ARG_IMAGE( class, "out", 100, 
 		_( "Output" ), 
diff --git a/libvips/colour/colour.c b/libvips/colour/colour.c
index cbf177e1..3d31e2bb 100644
--- a/libvips/colour/colour.c
+++ b/libvips/colour/colour.c
@@ -356,7 +356,7 @@ vips_colour_class_init( VipsColourClass *class )
 	vobject_class->description = _( "colour operations" );
 	vobject_class->build = vips_colour_build;
 
-	operation_class->flags = VIPS_OPERATION_SEQUENTIAL;
+	operation_class->flags = VIPS_OPERATION_SEQUENTIAL_UNBUFFERED;
 
 	VIPS_ARG_IMAGE( class, "out", 100, 
 		_( "Output" ), 
diff --git a/libvips/colour/colourspace.c b/libvips/colour/colourspace.c
index 42d1feb1..1ae1e721 100644
--- a/libvips/colour/colourspace.c
+++ b/libvips/colour/colourspace.c
@@ -328,7 +328,7 @@ vips_colourspace_class_init( VipsColourspaceClass *class )
 	vobject_class->description = _( "convert to a new colourspace" );
 	vobject_class->build = vips_colourspace_build;
 
-	operation_class->flags = VIPS_OPERATION_SEQUENTIAL;
+	operation_class->flags = VIPS_OPERATION_SEQUENTIAL_UNBUFFERED;
 
 	VIPS_ARG_IMAGE( class, "in", 1, 
 		_( "Input" ), 
diff --git a/libvips/conversion/bandary.c b/libvips/conversion/bandary.c
index bd9eb894..5e4e4f0b 100644
--- a/libvips/conversion/bandary.c
+++ b/libvips/conversion/bandary.c
@@ -178,7 +178,7 @@ vips_bandary_class_init( VipsBandaryClass *class )
 	vobject_class->description = _( "operations on image bands" );
 	vobject_class->build = vips_bandary_build;
 
-	operation_class->flags = VIPS_OPERATION_SEQUENTIAL;
+	operation_class->flags = VIPS_OPERATION_SEQUENTIAL_UNBUFFERED;
 }
 
 static void
diff --git a/libvips/conversion/cast.c b/libvips/conversion/cast.c
index 84746321..38df919a 100644
--- a/libvips/conversion/cast.c
+++ b/libvips/conversion/cast.c
@@ -477,7 +477,7 @@ vips_cast_class_init( VipsCastClass *class )
 	vobject_class->description = _( "cast an image" );
 	vobject_class->build = vips_cast_build;
 
-	operation_class->flags = VIPS_OPERATION_SEQUENTIAL;
+	operation_class->flags = VIPS_OPERATION_SEQUENTIAL_UNBUFFERED;
 
 	VIPS_ARG_IMAGE( class, "in", 1, 
 		_( "Input" ), 
diff --git a/libvips/conversion/conversion.c b/libvips/conversion/conversion.c
index 4e94d75b..4b00a8eb 100644
--- a/libvips/conversion/conversion.c
+++ b/libvips/conversion/conversion.c
@@ -69,6 +69,81 @@
  *
  */
 
+/** 
+ * VipsAlign:
+ * @VIPS_ALIGN_LOW: align low coordinate edge
+ * @VIPS_ALIGN_CENTRE: align centre
+ * @VIPS_ALIGN_HIGH: align high coordinate edge
+ *
+ * See vips_join() and so on.
+ *
+ * Operations like vips_join() need to be told whether to align images on the
+ * low or high coordinate edge, or centre.
+ *
+ * See also: vips_join().
+ */
+
+/** 
+ * VipsAngle:
+ * @VIPS_ANGLE_0: no rotate
+ * @VIPS_ANGLE_90: 90 degrees anti-clockwise
+ * @VIPS_ANGLE_180: 180 degree rotate
+ * @VIPS_ANGLE_270: 90 degrees clockwise
+ *
+ * See vips_rot() and so on.
+ *
+ * Fixed rotate angles.
+ *
+ * See also: vips_rot().
+ */
+
+/** 
+ * VipsExtend:
+ * @VIPS_EXTEND_BLACK: extend with black (all 0) pixels
+ * @VIPS_EXTEND_COPY: copy the image edges
+ * @VIPS_EXTEND_REPEAT: repeat the whole image
+ * @VIPS_EXTEND_MIRROR: mirror the whole image
+ * @VIPS_EXTEND_WHITE: extend with white (all bits set) pixels
+ * @VIPS_EXTEND_BACKGROUND: extend with colour from the @background property
+ *
+ * See vips_embed(), vips_conv(), vips_affine() and so on.
+ *
+ * When the edges of an image are extended, you can specify
+ * how you want the extension done. 
+ *
+ * #VIPS_EXTEND_BLACK --- new pixels are black, ie. all bits are zero. 
+ *
+ * #VIPS_EXTEND_COPY --- each new pixel takes the value of the nearest edge
+ * pixel
+ *
+ * #VIPS_EXTEND_REPEAT --- the image is tiled to fill the new area
+ *
+ * #VIPS_EXTEND_MIRROR --- the image is reflected and tiled to reduce hash
+ * edges
+ *
+ * #VIPS_EXTEND_WHITE --- new pixels are white, ie. all bits are set
+ *
+ * #VIPS_EXTEND_BACKGROUND --- colour set from the @background property
+ *
+ * We have to specify the exact value of each enum member since we have to 
+ * keep these frozen for back compat with vips7.
+ *
+ * See also: vips_embed().
+ */
+
+/** 
+ * VipsDirection:
+ * @VIPS_DIRECTION_HORIZONTAL: left-right 
+ * @VIPS_DIRECTION_VERTICAL: top-bottom
+ *
+ * See vips_flip(), vips_join() and so on.
+ *
+ * Operations like vips_flip() need to be told whether to flip left-right or
+ * top-bottom. 
+ *
+ * See also: vips_flip(), vips_join().
+ */
+
 G_DEFINE_ABSTRACT_TYPE( VipsConversion, vips_conversion, VIPS_TYPE_OPERATION );
 
 static int
diff --git a/libvips/conversion/copy.c b/libvips/conversion/copy.c
index 57c58f69..2b3981a9 100644
--- a/libvips/conversion/copy.c
+++ b/libvips/conversion/copy.c
@@ -320,7 +320,7 @@ vips_copy_class_init( VipsCopyClass *class )
 	 * cache it. Plus copy is cheap.
 	 */
 	operation_class->flags = 
-		VIPS_OPERATION_SEQUENTIAL | 
+		VIPS_OPERATION_SEQUENTIAL_UNBUFFERED | 
 		VIPS_OPERATION_NOCACHE;
 
 	VIPS_ARG_IMAGE( class, "in", 1, 
diff --git a/libvips/conversion/embed.c b/libvips/conversion/embed.c
index 9e0dacb7..8f33e248 100644
--- a/libvips/conversion/embed.c
+++ b/libvips/conversion/embed.c
@@ -545,7 +545,7 @@ vips_embed_class_init( VipsEmbedClass *class )
 	vobject_class->description = _( "embed an image in a larger image" );
 	vobject_class->build = vips_embed_build;
 
-	operation_class->flags = VIPS_OPERATION_SEQUENTIAL;
+	operation_class->flags = VIPS_OPERATION_SEQUENTIAL_UNBUFFERED;
 
 	VIPS_ARG_IMAGE( class, "in", -1, 
 		_( "Input" ), 
diff --git a/libvips/conversion/extract.c b/libvips/conversion/extract.c
index e99ee5ef..5f3a00bf 100644
--- a/libvips/conversion/extract.c
+++ b/libvips/conversion/extract.c
@@ -194,7 +194,7 @@ vips_extract_area_class_init( VipsExtractAreaClass *class )
 	vobject_class->description = _( "extract an area from an image" );
 	vobject_class->build = vips_extract_area_build;
 
-	operation_class->flags = VIPS_OPERATION_SEQUENTIAL;
+	operation_class->flags = VIPS_OPERATION_SEQUENTIAL_UNBUFFERED;
 
 	VIPS_ARG_IMAGE( class, "input", 0, 
 		_( "Input" ), 
diff --git a/libvips/conversion/falsecolour.c b/libvips/conversion/falsecolour.c
index d522744a..697c7125 100644
--- a/libvips/conversion/falsecolour.c
+++ b/libvips/conversion/falsecolour.c
@@ -369,7 +369,7 @@ vips_falsecolour_class_init( VipsFalsecolourClass *class )
 	vobject_class->description = _( "false colour an image" );
 	vobject_class->build = vips_falsecolour_build;
 
-	operation_class->flags = VIPS_OPERATION_SEQUENTIAL;
+	operation_class->flags = VIPS_OPERATION_SEQUENTIAL_UNBUFFERED;
 
 	VIPS_ARG_IMAGE( class, "in", 0, 
 		_( "in" ), 
diff --git a/libvips/conversion/flatten.c b/libvips/conversion/flatten.c
index 3b16673d..352e3734 100644
--- a/libvips/conversion/flatten.c
+++ b/libvips/conversion/flatten.c
@@ -371,7 +371,7 @@ vips_flatten_class_init( VipsFlattenClass *class )
 	vobject_class->description = _( "flatten alpha out of an image" );
 	vobject_class->build = vips_flatten_build;
 
-	operation_class->flags = VIPS_OPERATION_SEQUENTIAL;
+	operation_class->flags = VIPS_OPERATION_SEQUENTIAL_UNBUFFERED;
 
 	VIPS_ARG_IMAGE( class, "in", 1, 
 		_( "Input" ), 
diff --git a/libvips/conversion/gammacorrect.c b/libvips/conversion/gammacorrect.c
index 6de28524..bd7b5bed 100644
--- a/libvips/conversion/gammacorrect.c
+++ b/libvips/conversion/gammacorrect.c
@@ -105,7 +105,7 @@ vips_gammacorrect_class_init( VipsGammacorrectClass *class )
 	vobject_class->description = _( "gammacorrect a pair of images" );
 	vobject_class->build = vips_gammacorrect_build;
 
-	operation_class->flags = VIPS_OPERATION_SEQUENTIAL;
+	operation_class->flags = VIPS_OPERATION_SEQUENTIAL_UNBUFFERED;
 
 	VIPS_ARG_IMAGE( class, "in", -1, 
 		_( "in" ), 
diff --git a/libvips/conversion/ifthenelse.c b/libvips/conversion/ifthenelse.c
index 3f2cbd66..450cfd3a 100644
--- a/libvips/conversion/ifthenelse.c
+++ b/libvips/conversion/ifthenelse.c
@@ -471,7 +471,7 @@ vips_ifthenelse_class_init( VipsIfthenelseClass *class )
 	vobject_class->description = _( "ifthenelse an image" );
 	vobject_class->build = vips_ifthenelse_build;
 
-	operation_class->flags = VIPS_OPERATION_SEQUENTIAL;
+	operation_class->flags = VIPS_OPERATION_SEQUENTIAL_UNBUFFERED;
 
 	VIPS_ARG_IMAGE( class, "cond", -2, 
 		_( "Condition" ), 
diff --git a/libvips/conversion/insert.c b/libvips/conversion/insert.c
index 15ab5197..4b1fbbf9 100644
--- a/libvips/conversion/insert.c
+++ b/libvips/conversion/insert.c
@@ -355,7 +355,7 @@ vips_insert_class_init( VipsInsertClass *class )
 	vobject_class->description = _( "insert an image" );
 	vobject_class->build = vips_insert_build;
 
-	operation_class->flags = VIPS_OPERATION_SEQUENTIAL;
+	operation_class->flags = VIPS_OPERATION_SEQUENTIAL_UNBUFFERED;
 
 	VIPS_ARG_IMAGE( class, "main", -1, 
 		_( "Main" ), 
diff --git a/libvips/conversion/join.c b/libvips/conversion/join.c
index 3f125680..ad1ab9e3 100644
--- a/libvips/conversion/join.c
+++ b/libvips/conversion/join.c
@@ -228,7 +228,7 @@ vips_join_class_init( VipsJoinClass *class )
 	vobject_class->description = _( "join a pair of images" );
 	vobject_class->build = vips_join_build;
 
-	operation_class->flags = VIPS_OPERATION_SEQUENTIAL;
+	operation_class->flags = VIPS_OPERATION_SEQUENTIAL_UNBUFFERED;
 
 	VIPS_ARG_IMAGE( class, "in1", -1, 
 		_( "in1" ), 
diff --git a/libvips/conversion/msb.c b/libvips/conversion/msb.c
index 4eadae1e..cefb366b 100644
--- a/libvips/conversion/msb.c
+++ b/libvips/conversion/msb.c
@@ -1,4 +1,4 @@
-/* im_msb
+/* vips_msb()
  *
  * Copyright: 2006, The Nottingham Trent University
  *
@@ -239,7 +239,7 @@ vips_msb_class_init( VipsMsbClass *class )
 		_( "pick most-significant byte from an image" );
 	vobject_class->build = vips_msb_build;
 
-	operation_class->flags = VIPS_OPERATION_SEQUENTIAL;
+	operation_class->flags = VIPS_OPERATION_SEQUENTIAL_UNBUFFERED;
 
 	VIPS_ARG_IMAGE( class, "in", 0, 
 		_( "Input" ), 
diff --git a/libvips/conversion/recomb.c b/libvips/conversion/recomb.c
index 76d6e3f4..abc2b265 100644
--- a/libvips/conversion/recomb.c
+++ b/libvips/conversion/recomb.c
@@ -196,7 +196,7 @@ vips_recomb_class_init( VipsRecombClass *class )
 	object_class->description = _( "linear recombination with matrix" );
 	object_class->build = vips_recomb_build;
 
-	operation_class->flags = VIPS_OPERATION_SEQUENTIAL;
+	operation_class->flags = VIPS_OPERATION_SEQUENTIAL_UNBUFFERED;
 
 	VIPS_ARG_IMAGE( class, "in", 0, 
 		_( "Input" ), 
diff --git a/libvips/conversion/sequential.c b/libvips/conversion/sequential.c
index 17cd68d7..d5b473f5 100644
--- a/libvips/conversion/sequential.c
+++ b/libvips/conversion/sequential.c
@@ -76,6 +76,7 @@ typedef struct _VipsSequential {
 
 	VipsImage *in;
 	int tile_height;
+	VipsAccess access;
 	gboolean trace;
 
 	/* Lock access to y_pos with this, use the cond to wake up stalled
@@ -266,7 +267,7 @@ vips_sequential_build( VipsObject *object )
 
 	if( vips_linecache( sequential->in, &t, 
 		"tile_height", sequential->tile_height,
-		"strategy", VIPS_CACHE_SEQUENTIAL,
+		"access", sequential->access,
 		NULL ) )
 		return( -1 );
 
@@ -319,12 +320,20 @@ vips_sequential_class_init( VipsSequentialClass *class )
 		VIPS_ARGUMENT_OPTIONAL_INPUT,
 		G_STRUCT_OFFSET( VipsSequential, tile_height ),
 		1, 1000000, 1 );
+
+	VIPS_ARG_ENUM( class, "access", 6, 
+		_( "Strategy" ), 
+		_( "Expected access pattern" ),
+		VIPS_ARGUMENT_OPTIONAL_INPUT,
+		G_STRUCT_OFFSET( VipsSequential, access ),
+		VIPS_TYPE_ACCESS, VIPS_ACCESS_SEQUENTIAL );
 }
 
 static void
 vips_sequential_init( VipsSequential *sequential )
 {
 	sequential->trace = FALSE;
+	sequential->access = VIPS_ACCESS_SEQUENTIAL;
 	sequential->lock = vips_g_mutex_new();
 	sequential->ready = vips_g_cond_new();
 	sequential->tile_height = 1;
@@ -341,6 +350,7 @@ vips_sequential_init( VipsSequential *sequential )
  *
  * @trace: trace requests
  * @strip_height: height of cache strips
+ * @access: access pattern
  *
  * This operation behaves rather like vips_copy() between images
  * @in and @out, except that it checks that pixels are only requested
@@ -357,6 +367,9 @@ vips_sequential_init( VipsSequential *sequential )
  * @strip_height can be used to set the size of the tiles that
  * vips_sequential() uses. The default value is 1.
  *
+ * @access can be set to #VIPS_ACCESS_SEQUENTIAL_UNBUFFERED, meaning don't
+ * keep a large cache behind the read point. This can save some memory. 
+ *
  * See also: vips_image_cache().
  *
  * Returns: 0 on success, -1 on error.
diff --git a/libvips/conversion/tilecache.c b/libvips/conversion/tilecache.c
index e9d857da..52c63c2b 100644
--- a/libvips/conversion/tilecache.c
+++ b/libvips/conversion/tilecache.c
@@ -119,7 +119,7 @@ typedef struct _VipsBlockCache {
 	int tile_width;	
 	int tile_height;
 	int max_tiles;
-	VipsCacheStrategy strategy;
+	VipsAccess access;
 	gboolean threaded;
 	gboolean persistent;
 
@@ -261,15 +261,16 @@ vips_tile_search_recycle( gpointer key, gpointer value, gpointer user_data )
 	/* Only consider unreffed tiles for recycling.
 	 */
 	if( !tile->ref_count ) {
-		switch( cache->strategy ) {
-		case VIPS_CACHE_RANDOM:
+		switch( cache->access ) {
+		case VIPS_ACCESS_RANDOM:
 			if( tile->time < search->oldest ) {
 				search->oldest = tile->time;
 				search->tile = tile;
 			}
 			break;
 
-		case VIPS_CACHE_SEQUENTIAL:
+		case VIPS_ACCESS_SEQUENTIAL:
+		case VIPS_ACCESS_SEQUENTIAL_UNBUFFERED:
 			if( tile->pos.top < search->topmost ) {
 				search->topmost = tile->pos.top;
 				search->tile = tile;
@@ -410,12 +411,12 @@ vips_block_cache_class_init( VipsBlockCacheClass *class )
 		G_STRUCT_OFFSET( VipsBlockCache, tile_height ),
 		1, 1000000, 128 );
 
-	VIPS_ARG_ENUM( class, "strategy", 6, 
-		_( "Strategy" ), 
+	VIPS_ARG_ENUM( class, "access", 6, 
+		_( "Access" ), 
 		_( "Expected access pattern" ),
 		VIPS_ARGUMENT_OPTIONAL_INPUT,
-		G_STRUCT_OFFSET( VipsBlockCache, strategy ),
-		VIPS_TYPE_CACHE_STRATEGY, VIPS_CACHE_RANDOM );
+		G_STRUCT_OFFSET( VipsBlockCache, access ),
+		VIPS_TYPE_ACCESS, VIPS_ACCESS_RANDOM );
 
 	VIPS_ARG_BOOL( class, "threaded", 7, 
 		_( "Threaded" ), 
@@ -476,7 +477,7 @@ vips_block_cache_init( VipsBlockCache *cache )
 	cache->tile_width = 128;
 	cache->tile_height = 128;
 	cache->max_tiles = 1000;
-	cache->strategy = VIPS_CACHE_RANDOM;
+	cache->access = VIPS_ACCESS_RANDOM;
 	cache->threaded = FALSE;
 	cache->persistent = FALSE;
 
@@ -799,7 +800,7 @@ vips_tile_cache_init( VipsTileCache *cache )
  * @tile_width: width of tiles in cache
  * @tile_height: height of tiles in cache
  * @max_tiles: maximum number of tiles to cache
- * @strategy: hint expected access pattern #VipsCacheStrategy
+ * @access: hint expected access pattern #VipsAccess
  * @threaded: allow many threads
  * @persistent: don't drop cache at end of computation
  *
@@ -812,12 +813,13 @@ vips_tile_cache_init( VipsTileCache *cache )
  * Each cache tile is made with a single call to 
  * vips_image_prepare(). 
  *
- * When the cache fills, a tile is chosen for reuse. If @strategy is
- * #VIPS_CACHE_RANDOM, then the least-recently-used tile is reused. If 
- * @strategy is #VIPS_CACHE_SEQUENTIAL, the top-most tile is reused.
+ * When the cache fills, a tile is chosen for reuse. If @access is
+ * #VIPS_ACCESS_RANDOM, then the least-recently-used tile is reused. If 
+ * @access is #VIPS_ACCESS_SEQUENTIAL or #VIPS_ACCESS_SEQUENTIAL_UNBUFFERED, 
+ * the top-most tile is reused.
  *
  * By default, @tile_width and @tile_height are 128 pixels, and the operation
- * will cache up to 1,000 tiles. @strategy defaults to #VIPS_CACHE_RANDOM.
+ * will cache up to 1,000 tiles. @access defaults to #VIPS_ACCESS_RANDOM.
  *
  * Normally, only a single thread at once is allowed to calculate tiles. If
  * you set @threaded to %TRUE, vips_tilecache() will allow many threads to
@@ -846,6 +848,8 @@ vips_tilecache( VipsImage *in, VipsImage **out, ... )
 typedef struct _VipsLineCache {
 	VipsBlockCache parent_instance;
 
+	VipsAccess access;
+
 } VipsLineCache;
 
 typedef VipsBlockCacheClass VipsLineCacheClass;
@@ -863,9 +867,12 @@ vips_line_cache_gen( VipsRegion *or,
 	/* We size up the cache to the largest request.
 	 */
 	if( or->valid.height > 
-		block_cache->max_tiles * block_cache->tile_height ) 
+		block_cache->max_tiles * block_cache->tile_height ) {
 		block_cache->max_tiles = 
 			1 + (or->valid.height / block_cache->tile_height);
+		VIPS_DEBUG_MSG( "vips_line_cache_gen: bumped max_tiles to %d\n",
+			block_cache->max_tiles ); 
+	}
 
 	g_mutex_unlock( block_cache->lock );
 
@@ -879,10 +886,6 @@ vips_line_cache_build( VipsObject *object )
 	VipsBlockCache *block_cache = (VipsBlockCache *) object;
 	VipsLineCache *cache = (VipsLineCache *) object;
 
-	int tile_width;
-	int tile_height;
-	int nlines;
-
 	VIPS_DEBUG_MSG( "vips_line_cache_build\n" );
 
 	if( VIPS_OBJECT_CLASS( vips_line_cache_parent_class )->
@@ -893,18 +896,32 @@ vips_line_cache_build( VipsObject *object )
 	 */
 	block_cache->tile_width = block_cache->in->Xsize;
 
-	/* Enough lines for two complete buffers would be exactly right. Make
-	 * it 3 to give us some slop room. 
-	 *
-	 * This can go up with request size, see vips_line_cache_gen().
-	 */
-	vips_get_tile_size( block_cache->in, 
-		&tile_width, &tile_height, &nlines );
-	block_cache->max_tiles = 3 * (1 + nlines / block_cache->tile_height);
+	block_cache->access = cache->access; 
 
-	VIPS_DEBUG_MSG( "vips_line_cache_build: max_tiles = %d, "
-		"tile_height = %d, nlines = %d\n",
-		block_cache->max_tiles, block_cache->tile_height, nlines );
+	if( cache->access == VIPS_ACCESS_SEQUENTIAL_UNBUFFERED )
+		block_cache->max_tiles = 1; 
+	else { 
+		/* Enough lines for two complete buffers would be exactly 
+		 * right. Make it 3 to give us some slop room. 
+		 *
+		 * This can go up with request size, see vips_line_cache_gen().
+		 */
+		int tile_width;
+		int tile_height;
+		int nlines;
+
+		vips_get_tile_size( block_cache->in, 
+			&tile_width, &tile_height, &nlines );
+		block_cache->max_tiles = 3 * 
+			(1 + nlines / block_cache->tile_height);
+
+		VIPS_DEBUG_MSG( "vips_line_cache_build: nlines = %d\n", 
+			nlines );
+	}
+
+	VIPS_DEBUG_MSG( "vips_line_cache_build: "
+		"max_tiles = %d, tile_height = %d\n", 
+		block_cache->max_tiles, block_cache->tile_height ); 
 
 	if( vips_image_pio_input( block_cache->in ) )
 		return( -1 );
@@ -937,11 +954,19 @@ vips_line_cache_class_init( VipsLineCacheClass *class )
 	vobject_class->description = _( "cache an image as a set of lines" );
 	vobject_class->build = vips_line_cache_build;
 
+	VIPS_ARG_ENUM( class, "access", 6, 
+		_( "Access" ), 
+		_( "Expected access pattern" ),
+		VIPS_ARGUMENT_OPTIONAL_INPUT,
+		G_STRUCT_OFFSET( VipsLineCache, access ),
+		VIPS_TYPE_ACCESS, VIPS_ACCESS_SEQUENTIAL );
+
 }
 
 static void
 vips_line_cache_init( VipsLineCache *cache )
 {
+	cache->access = VIPS_ACCESS_SEQUENTIAL;
 }
 
 /**
@@ -952,29 +977,31 @@ vips_line_cache_init( VipsLineCache *cache )
  *
  * Optional arguments:
  *
- * @strategy: hint expected access pattern #VipsCacheStrategy
+ * @access: hint expected access pattern #VipsAccess
  * @tile_height: height of tiles in cache
  * @threaded: allow many threads
  *
  * This operation behaves rather like vips_copy() between images
- * @in and @out, except that it keeps a cache of computed pixels. 
- * This cache is made of a set of scanlines. The number of lines cached is
- * equal to the maximum prepare request.
+ * @in and @out, except that it keeps a cache of computed scanlines. 
+ *
+ * The number of lines cached is enough for a small amount of non-local
+ * access. If you know you will not be making any non-local access, you can
+ * save some memory and set @access to #VIPS_ACCESS_SEQUENTIAL_UNBUFFERED. 
  *
  * Each cache tile is made with a single call to 
  * vips_image_prepare(). 
  *
- * When the cache fills, a tile is chosen for reuse. If @strategy is
- * #VIPS_CACHE_RANDOM, then the least-recently-used tile is reused. If 
- * @strategy is #VIPS_CACHE_SEQUENTIAL, the top-most tile is reused.
- * @strategy defaults to #VIPS_CACHE_RANDOM.
+ * When the cache fills, a tile is chosen for reuse. If @access is
+ * #VIPS_ACCESS_RANDOM, then the least-recently-used tile is reused. If 
+ * @access is #VIPS_ACCESS_SEQUENTIAL or #VIPS_ACCESS_SEQUENTIAL_UNBUFFERED, 
+ * the top-most tile is reused. @access defaults to #VIPS_ACCESS_RANDOM.
  *
  * @tile_height can be used to set the size of the strips that
  * vips_linecache() uses. The default is 1 (a single scanline).
  *
  * Normally, only a single thread at once is allowed to calculate tiles. If
  * you set @threaded to %TRUE, vips_linecache() will allow many threads to
- * calculate tiles at once, and share the cache between them.
+ * calculate tiles at once and share the cache between them.
  *
  * See also: vips_cache(), vips_tilecache(). 
  *
diff --git a/libvips/conversion/zoom.c b/libvips/conversion/zoom.c
index 07ae476e..0e7553f5 100644
--- a/libvips/conversion/zoom.c
+++ b/libvips/conversion/zoom.c
@@ -386,7 +386,7 @@ vips_zoom_class_init( VipsZoomClass *class )
 	vobject_class->description = _( "zoom an image" );
 	vobject_class->build = vips_zoom_build;
 
-	operation_class->flags = VIPS_OPERATION_SEQUENTIAL;
+	operation_class->flags = VIPS_OPERATION_SEQUENTIAL_UNBUFFERED;
 
 	VIPS_ARG_IMAGE( class, "input", 0, 
 		_( "Input" ), 
diff --git a/libvips/deprecated/im_jpeg2vips.c b/libvips/deprecated/im_jpeg2vips.c
index 8ba81b3b..eda579fb 100644
--- a/libvips/deprecated/im_jpeg2vips.c
+++ b/libvips/deprecated/im_jpeg2vips.c
@@ -115,7 +115,7 @@ jpeg2vips( const char *name, IMAGE *out, gboolean header_only )
 
 #ifdef HAVE_JPEG
 	if( vips__jpeg_read_file( filename, out, 
-		header_only, shrink, fail_on_warn ) )
+		header_only, shrink, fail_on_warn, TRUE ) )
 		return( -1 );
 #else
 	vips_error( "im_jpeg2vips", 
diff --git a/libvips/deprecated/im_png2vips.c b/libvips/deprecated/im_png2vips.c
index 39e84bc7..deaa32cc 100644
--- a/libvips/deprecated/im_png2vips.c
+++ b/libvips/deprecated/im_png2vips.c
@@ -87,7 +87,7 @@ png2vips( const char *name, IMAGE *out, gboolean header_only )
 			return( -1 );
 	}
 	else {
-		if( vips__png_read( filename, out ) )
+		if( vips__png_read( filename, out, TRUE ) )
 			return( -1 );
 	}
 #else
diff --git a/libvips/deprecated/im_tiff2vips.c b/libvips/deprecated/im_tiff2vips.c
index f6678f7a..1bb1c90d 100644
--- a/libvips/deprecated/im_tiff2vips.c
+++ b/libvips/deprecated/im_tiff2vips.c
@@ -98,7 +98,7 @@ tiff2vips( const char *name, IMAGE *out, gboolean header_only )
 			return( -1 );
 	}
 	else {
-		if( vips__tiff_read( filename, out, page ) )
+		if( vips__tiff_read( filename, out, page, TRUE ) )
 			return( -1 );
 	}
 #else
diff --git a/libvips/deprecated/vips7compat.c b/libvips/deprecated/vips7compat.c
index 154d372f..062c2b06 100644
--- a/libvips/deprecated/vips7compat.c
+++ b/libvips/deprecated/vips7compat.c
@@ -3770,7 +3770,7 @@ im_tile_cache( IMAGE *in, IMAGE *out,
 		"tile_width", tile_width, 
 		"tile_height", tile_height, 
 		"max_tiles", max_tiles, 
-		"strategy", VIPS_CACHE_SEQUENTIAL,
+		"access", VIPS_ACCESS_SEQUENTIAL,
 		"threaded", TRUE, 
 		NULL ) )
 		return( -1 );
diff --git a/libvips/foreign/foreign.c b/libvips/foreign/foreign.c
index 5b92723b..edf72480 100644
--- a/libvips/foreign/foreign.c
+++ b/libvips/foreign/foreign.c
@@ -135,26 +135,6 @@
  * need to swap bytes. See vips_copy().
  */
 
-/** 
- * VipsForeignAccess:
- * @VIPS_FOREIGN_ACCESS_RANDOM: can read anywhere
- * @VIPS_FOREIGN_ACCESS_SEQUENTIAL: top-to-bottom reading only, but with a small buffer
- * @VIPS_FOREIGN_ACCESS_SEQUENTIAL_UNBUFFERED: top-to-bottom reading only
- *
- * Set this flag on a loader to indicate the type of access you need. 
- *
- * @VIPS_FOREIGN_ACCESS_RANDOM means you require full random access to the 
- * image. This is usually the most expensive type of access to provide. 
- *
- * @VIPS_FOREIGN_ACCESS_SEQUENTIAL means you only need need top-to-bottom 
- * reading, but you need a smll buffer (a few hundred scanlines) behind the 
- * read point. 
- *
- * @VIPS_FOREIGN_ACCESS_SEQUENTIAL_UNBUFFERED means you only need 
- * top-to-bottom access. This is usually the cheapest type of access to 
- * provide. 
- */
-
 /**
  * VipsForeignClass:
  *
@@ -705,7 +685,7 @@ vips_foreign_load_temp( VipsForeignLoad *load )
 	 * directly.
 	 */
 	if( (load->flags & VIPS_FOREIGN_SEQUENTIAL) && 
-		load->access != VIPS_FOREIGN_ACCESS_RANDOM ) {
+		load->access != VIPS_ACCESS_RANDOM ) {
 #ifdef DEBUG
 		printf( "vips_foreign_load_temp: partial sequential temp\n" );
 #endif /*DEBUG*/
@@ -961,7 +941,7 @@ vips_foreign_load_class_init( VipsForeignLoadClass *class )
 		_( "Required access pattern for this file" ),
 		VIPS_ARGUMENT_OPTIONAL_INPUT,
 		G_STRUCT_OFFSET( VipsForeignLoad, access ),
-		VIPS_TYPE_FOREIGN_ACCESS, VIPS_FOREIGN_ACCESS_RANDOM ); 
+		VIPS_TYPE_ACCESS, VIPS_ACCESS_RANDOM ); 
 
 	VIPS_ARG_BOOL( class, "sequential", 10, 
 		_( "Sequential" ), 
@@ -976,7 +956,7 @@ static void
 vips_foreign_load_init( VipsForeignLoad *load )
 {
 	load->disc = TRUE;
-	load->access = VIPS_FOREIGN_ACCESS_RANDOM;
+	load->access = VIPS_ACCESS_RANDOM;
 }
 
 /* Abstract base class for image savers.
diff --git a/libvips/foreign/jpeg.h b/libvips/foreign/jpeg.h
index b8a9f793..ac0f6f3c 100644
--- a/libvips/foreign/jpeg.h
+++ b/libvips/foreign/jpeg.h
@@ -60,11 +60,9 @@ int vips__jpeg_write_buffer( VipsImage *in,
 
 int vips__isjpeg( const char *filename );
 int vips__jpeg_read_file( const char *name, VipsImage *out, 
-	gboolean header_only,
-	int shrink, gboolean fail );
+	gboolean header_only, int shrink, gboolean fail, gboolean readbehind );
 int vips__jpeg_read_buffer( void *buf, size_t len, VipsImage *out, 
-	gboolean header_only,
-	int shrink, int fail );
+	gboolean header_only, int shrink, int fail, gboolean readbehind );
 
 #ifdef __cplusplus
 }
diff --git a/libvips/foreign/jpeg2vips.c b/libvips/foreign/jpeg2vips.c
index 777088e2..50fd43d3 100644
--- a/libvips/foreign/jpeg2vips.c
+++ b/libvips/foreign/jpeg2vips.c
@@ -144,6 +144,10 @@ typedef struct _ReadJpeg {
 	 */
 	gboolean fail;
 
+	/* Use a read behind buffer.
+	 */
+	gboolean readbehind; 
+
 	/* Used for file input only.
 	 */
 	char *filename;
@@ -208,7 +212,7 @@ readjpeg_close( VipsObject *object, ReadJpeg *jpeg )
 }
 
 static ReadJpeg *
-readjpeg_new( VipsImage *out, int shrink, gboolean fail )
+readjpeg_new( VipsImage *out, int shrink, gboolean fail, gboolean readbehind )
 {
 	ReadJpeg *jpeg;
 
@@ -218,6 +222,7 @@ readjpeg_new( VipsImage *out, int shrink, gboolean fail )
 	jpeg->out = out;
 	jpeg->shrink = shrink;
 	jpeg->fail = fail;
+	jpeg->readbehind = readbehind;
 	jpeg->filename = NULL;
 	jpeg->decompressing = FALSE;
 
@@ -959,6 +964,9 @@ read_jpeg_image( ReadJpeg *jpeg, VipsImage *out )
 		jpeg, NULL ) ||
 		vips_sequential( t[0], &t[1], 
 			"tile_height", 8,
+			"access", jpeg->readbehind ? 
+				VIPS_ACCESS_SEQUENTIAL : 
+				VIPS_ACCESS_SEQUENTIAL_UNBUFFERED,
 			NULL ) ||
 		vips_image_write( t[1], out ) )
 		return( -1 );
@@ -970,12 +978,12 @@ read_jpeg_image( ReadJpeg *jpeg, VipsImage *out )
  */
 int
 vips__jpeg_read_file( const char *filename, VipsImage *out, 
-	gboolean header_only, int shrink, gboolean fail )
+	gboolean header_only, int shrink, gboolean fail, gboolean readbehind )
 {
 	ReadJpeg *jpeg;
 	int result;
 
-	if( !(jpeg = readjpeg_new( out, shrink, fail )) )
+	if( !(jpeg = readjpeg_new( out, shrink, fail, readbehind )) )
 		return( -1 );
 
 	/* Here for longjmp() from vips__new_error_exit() during startup.
@@ -1189,12 +1197,12 @@ readjpeg_buffer (ReadJpeg *jpeg, void *buf, size_t len)
 
 int
 vips__jpeg_read_buffer( void *buf, size_t len, VipsImage *out, 
-	gboolean header_only, int shrink, int fail )
+	gboolean header_only, int shrink, int fail, gboolean readbehind )
 {
 	ReadJpeg *jpeg;
 	int result;
 
-	if( !(jpeg = readjpeg_new( out, shrink, fail )) )
+	if( !(jpeg = readjpeg_new( out, shrink, fail, readbehind )) )
 		return( -1 );
 
 	if( setjmp( jpeg->eman.jmp ) ) {
diff --git a/libvips/foreign/jpegload.c b/libvips/foreign/jpegload.c
index e9d80784..e89d66f3 100644
--- a/libvips/foreign/jpegload.c
+++ b/libvips/foreign/jpegload.c
@@ -199,7 +199,7 @@ vips_foreign_load_jpeg_file_header( VipsForeignLoad *load )
 	VipsForeignLoadJpegFile *file = (VipsForeignLoadJpegFile *) load;
 
 	if( vips__jpeg_read_file( file->filename, load->out, 
-		TRUE, jpeg->shrink, jpeg->fail ) )
+		TRUE, jpeg->shrink, jpeg->fail, FALSE ) ) 
 		return( -1 );
 
 	return( 0 );
@@ -212,7 +212,8 @@ vips_foreign_load_jpeg_file_load( VipsForeignLoad *load )
 	VipsForeignLoadJpegFile *file = (VipsForeignLoadJpegFile *) load;
 
 	if( vips__jpeg_read_file( file->filename, load->real, 
-		FALSE, jpeg->shrink, jpeg->fail ) )
+		FALSE, jpeg->shrink, jpeg->fail,
+		load->access == VIPS_ACCESS_SEQUENTIAL ) )
 		return( -1 );
 
 	return( 0 );
@@ -276,7 +277,7 @@ vips_foreign_load_jpeg_buffer_header( VipsForeignLoad *load )
 	VipsForeignLoadJpegBuffer *buffer = (VipsForeignLoadJpegBuffer *) load;
 
 	if( vips__jpeg_read_buffer( buffer->buf->data, buffer->buf->length, 
-		load->out, TRUE, jpeg->shrink, jpeg->fail ) )
+		load->out, TRUE, jpeg->shrink, jpeg->fail, FALSE ) )
 		return( -1 );
 
 	return( 0 );
@@ -289,7 +290,8 @@ vips_foreign_load_jpeg_buffer_load( VipsForeignLoad *load )
 	VipsForeignLoadJpegBuffer *buffer = (VipsForeignLoadJpegBuffer *) load;
 
 	if( vips__jpeg_read_buffer( buffer->buf->data, buffer->buf->length, 
-		load->real, FALSE, jpeg->shrink, jpeg->fail ) )
+		load->real, FALSE, jpeg->shrink, jpeg->fail,
+		load->access == VIPS_ACCESS_SEQUENTIAL ) )
 		return( -1 );
 
 	return( 0 );
diff --git a/libvips/foreign/pngload.c b/libvips/foreign/pngload.c
index cf49b6dd..a4954f66 100644
--- a/libvips/foreign/pngload.c
+++ b/libvips/foreign/pngload.c
@@ -104,7 +104,8 @@ vips_foreign_load_png_load( VipsForeignLoad *load )
 {
 	VipsForeignLoadPng *png = (VipsForeignLoadPng *) load;
 
-	if( vips__png_read( png->filename, load->real ) )
+	if( vips__png_read( png->filename, load->real, 
+		load->access == VIPS_ACCESS_SEQUENTIAL ) )
 		return( -1 );
 
 	return( 0 );
@@ -178,7 +179,7 @@ vips_foreign_load_png_buffer_load( VipsForeignLoad *load )
 	VipsForeignLoadPngBuffer *png = (VipsForeignLoadPngBuffer *) load;
 
 	if( vips__png_read_buffer( png->buf->data, png->buf->length, 
-		load->real ) )
+		load->real, load->access == VIPS_ACCESS_SEQUENTIAL ) )
 		return( -1 );
 
 	return( 0 );
diff --git a/libvips/foreign/tiff.h b/libvips/foreign/tiff.h
index 73cc0bfb..af8a308f 100644
--- a/libvips/foreign/tiff.h
+++ b/libvips/foreign/tiff.h
@@ -49,7 +49,8 @@ int vips__tiff_write( VipsImage *in, const char *filename,
 	VipsForeignTiffResunit resunit, double xres, double yres,
 	gboolean bigtiff );
 
-int vips__tiff_read( const char *filename, VipsImage *out, int page );
+int vips__tiff_read( const char *filename, VipsImage *out, int page, 
+	gboolean readbehind );
 int vips__tiff_read_header( const char *filename, VipsImage *out, int page );
 gboolean vips__istifftiled( const char *filename );
 gboolean vips__istiff( const char *filename );
diff --git a/libvips/foreign/tiff2vips.c b/libvips/foreign/tiff2vips.c
index 49749e8e..8367fc25 100644
--- a/libvips/foreign/tiff2vips.c
+++ b/libvips/foreign/tiff2vips.c
@@ -206,10 +206,8 @@ typedef struct _ReadTiff {
 	 */
 	char *filename;
 	VipsImage *out;
-
-	/* From filename.
-	 */
 	int page;
+	gboolean readbehind; 
 
 	/* The TIFF we read.
 	 */
@@ -1497,6 +1495,9 @@ read_stripwise( ReadTiff *rtiff, VipsImage *out )
 			rtiff, NULL ) ||
 		vips_sequential( t[0], &t[1], 
 			"tile_height", rtiff->rows_per_strip,
+			"access", rtiff->readbehind ? 
+				VIPS_ACCESS_SEQUENTIAL : 
+				VIPS_ACCESS_SEQUENTIAL_UNBUFFERED,
 			NULL ) ||
 		vips_image_write( t[1], out ) )
 		return( -1 );
@@ -1511,7 +1512,8 @@ readtiff_destroy( VipsObject *object, ReadTiff *rtiff )
 }
 
 static ReadTiff *
-readtiff_new( const char *filename, VipsImage *out, int page )
+readtiff_new( const char *filename, VipsImage *out, int page, 
+	gboolean readbehind )
 {
 	ReadTiff *rtiff;
 
@@ -1521,6 +1523,7 @@ readtiff_new( const char *filename, VipsImage *out, int page )
 	rtiff->filename = vips_strdup( VIPS_OBJECT( out ), filename );
 	rtiff->out = out;
 	rtiff->page = page;
+	rtiff->readbehind = readbehind;
 	rtiff->tiff = NULL;
 	rtiff->sfn = NULL;
 	rtiff->client = NULL;
@@ -1594,7 +1597,8 @@ istiffpyramid( const char *name )
  */
 
 int
-vips__tiff_read( const char *filename, VipsImage *out, int page )
+vips__tiff_read( const char *filename, VipsImage *out, int page, 
+	gboolean readbehind )
 {
 	ReadTiff *rtiff;
 
@@ -1605,7 +1609,7 @@ vips__tiff_read( const char *filename, VipsImage *out, int page )
 
 	vips__tiff_init();
 
-	if( !(rtiff = readtiff_new( filename, out, page )) )
+	if( !(rtiff = readtiff_new( filename, out, page, readbehind )) )
 		return( -1 );
 
 	if( !(rtiff->tiff = get_directory( rtiff->filename, rtiff->page )) ) {
@@ -1633,7 +1637,7 @@ vips__tiff_read_header( const char *filename, VipsImage *out, int page )
 
 	vips__tiff_init();
 
-	if( !(rtiff = readtiff_new( filename, out, page )) )
+	if( !(rtiff = readtiff_new( filename, out, page, FALSE )) )
 		return( -1 );
 
 	if( !(rtiff->tiff = get_directory( rtiff->filename, rtiff->page )) ) {
diff --git a/libvips/foreign/tiffload.c b/libvips/foreign/tiffload.c
index e1f3c6f5..cbcff533 100644
--- a/libvips/foreign/tiffload.c
+++ b/libvips/foreign/tiffload.c
@@ -108,7 +108,8 @@ vips_foreign_load_tiff_load( VipsForeignLoad *load )
 {
 	VipsForeignLoadTiff *tiff = (VipsForeignLoadTiff *) load;
 
-	if( vips__tiff_read( tiff->filename, load->real, tiff->page ) )
+	if( vips__tiff_read( tiff->filename, load->real, tiff->page, 
+		load->access == VIPS_ACCESS_SEQUENTIAL ) )
 		return( -1 );
 
 	return( 0 );
diff --git a/libvips/foreign/vipspng.c b/libvips/foreign/vipspng.c
index a403940c..02a87e38 100644
--- a/libvips/foreign/vipspng.c
+++ b/libvips/foreign/vipspng.c
@@ -126,6 +126,7 @@ user_warning_function( png_structp png_ptr, png_const_charp warning_msg )
 typedef struct {
 	char *name;
 	VipsImage *out;
+	gboolean readbehind; 
 
 	int y_pos;
 	png_structp pPng;
@@ -141,6 +142,7 @@ typedef struct {
 	char *buffer;
 	size_t length;
 	size_t read_pos;
+
 } Read;
 
 static void
@@ -153,7 +155,7 @@ read_destroy( VipsImage *out, Read *read )
 }
 
 static Read *
-read_new( VipsImage *out )
+read_new( VipsImage *out, gboolean readbehind )
 {
 	Read *read;
 
@@ -161,6 +163,7 @@ read_new( VipsImage *out )
 		return( NULL );
 
 	read->name = NULL;
+	read->readbehind = readbehind;
 	read->out = out;
 	read->y_pos = 0;
 	read->pPng = NULL;
@@ -191,11 +194,11 @@ read_new( VipsImage *out )
 }
 
 static Read *
-read_new_filename( VipsImage *out, const char *name )
+read_new_filename( VipsImage *out, const char *name, gboolean readbehind )
 {
 	Read *read;
 
-	if( !(read = read_new( out )) )
+	if( !(read = read_new( out, readbehind )) )
 		return( NULL );
 
 	read->name = vips_strdup( VIPS_OBJECT( out ), name );
@@ -393,7 +396,7 @@ vips__png_header( const char *name, VipsImage *out )
 {
 	Read *read;
 
-	if( !(read = read_new_filename( out, name )) ||
+	if( !(read = read_new_filename( out, name, FALSE )) ||
 		png2vips_header( read, out ) ) 
 		return( -1 );
 
@@ -492,7 +495,7 @@ vips__png_isinterlaced( const char *filename )
 	int interlace_type;
 
 	image = vips_image_new();
-	if( !(read = read_new_filename( image, filename )) ) {
+	if( !(read = read_new_filename( image, filename, FALSE )) ) {
 		g_object_unref( image );
 		return( -1 );
 	}
@@ -527,6 +530,9 @@ png2vips_image( Read *read, VipsImage *out )
 				read, NULL ) ||
 			vips_sequential( t[0], &t[1], 
 				"tile_height", 8,
+				"access", read->readbehind ? 
+					VIPS_ACCESS_SEQUENTIAL : 
+					VIPS_ACCESS_SEQUENTIAL_UNBUFFERED,
 				NULL ) ||
 			vips_image_write( t[1], out ) )
 			return( -1 );
@@ -536,7 +542,7 @@ png2vips_image( Read *read, VipsImage *out )
 }
 
 int
-vips__png_read( const char *filename, VipsImage *out )
+vips__png_read( const char *filename, VipsImage *out, gboolean readbehind )
 {
 	Read *read;
 
@@ -544,7 +550,7 @@ vips__png_read( const char *filename, VipsImage *out )
 	printf( "vips__png_read: reading \"%s\"\n", filename );
 #endif /*DEBUG*/
 
-	if( !(read = read_new_filename( out, filename )) ||
+	if( !(read = read_new_filename( out, filename, readbehind )) ||
 		png2vips_image( read, out ) )
 		return( -1 ); 
 
@@ -581,15 +587,16 @@ vips_png_read_buffer( png_structp pPng, png_bytep data, png_size_t length )
 }
 
 static Read *
-read_new_buffer( VipsImage *out, char *buffer, size_t length )
+read_new_buffer( VipsImage *out, char *buffer, size_t length, 
+	gboolean readbehind )
 {
 	Read *read;
 
-	if( !(read = read_new( out )) )
+	if( !(read = read_new( out, readbehind )) )
 		return( NULL );
 
-	read->buffer = buffer;
 	read->length = length;
+	read->buffer = buffer;
 
 	png_set_read_fn( read->pPng, read, vips_png_read_buffer ); 
 
@@ -606,7 +613,7 @@ vips__png_header_buffer( char *buffer, size_t length, VipsImage *out )
 {
 	Read *read;
 
-	if( !(read = read_new_buffer( out, buffer, length )) ||
+	if( !(read = read_new_buffer( out, buffer, length, FALSE )) ||
 		png2vips_header( read, out ) ) 
 		return( -1 );
 
@@ -614,11 +621,12 @@ vips__png_header_buffer( char *buffer, size_t length, VipsImage *out )
 }
 
 int
-vips__png_read_buffer( char *buffer, size_t length, VipsImage *out  )
+vips__png_read_buffer( char *buffer, size_t length, VipsImage *out, 
+	gboolean readbehind  )
 {
 	Read *read;
 
-	if( !(read = read_new_buffer( out, buffer, length )) ||
+	if( !(read = read_new_buffer( out, buffer, length, readbehind )) ||
 		png2vips_image( read, out ) )
 		return( -1 ); 
 
diff --git a/libvips/foreign/vipspng.h b/libvips/foreign/vipspng.h
index 9922eecd..051ac55b 100644
--- a/libvips/foreign/vipspng.h
+++ b/libvips/foreign/vipspng.h
@@ -36,11 +36,12 @@ extern "C" {
 #endif /*__cplusplus*/
 
 int vips__png_header( const char *name, VipsImage *out );
-int vips__png_read( const char *name, VipsImage *out );
+int vips__png_read( const char *name, VipsImage *out, gboolean readbehind );
 int vips__png_ispng( const char *filename );
 gboolean vips__png_isinterlaced( const char *filename );
 extern const char *vips__png_suffs[];
-int vips__png_read_buffer( char *buffer, size_t length, VipsImage *out  );
+int vips__png_read_buffer( char *buffer, size_t length, VipsImage *out, 
+	gboolean readbehind  );
 int vips__png_header_buffer( char *buffer, size_t length, VipsImage *out );
 
 int vips__png_write( VipsImage *in, const char *filename, 
diff --git a/libvips/histogram/maplut.c b/libvips/histogram/maplut.c
index 7316692a..2f92fc3d 100644
--- a/libvips/histogram/maplut.c
+++ b/libvips/histogram/maplut.c
@@ -606,7 +606,7 @@ vips_maplut_class_init( VipsMaplutClass *class )
 	object_class->description = _( "map an image though a lut" );
 	object_class->build = vips_maplut_build;
 
-	operation_class->flags = VIPS_OPERATION_SEQUENTIAL;
+	operation_class->flags = VIPS_OPERATION_SEQUENTIAL_UNBUFFERED;
 
 	VIPS_ARG_IMAGE( class, "in", 1, 
 		_( "Input" ), 
diff --git a/libvips/include/vips/conversion.h b/libvips/include/vips/conversion.h
index 320e9909..f2c891f6 100644
--- a/libvips/include/vips/conversion.h
+++ b/libvips/include/vips/conversion.h
@@ -38,39 +38,6 @@
 extern "C" {
 #endif /*__cplusplus*/
 
-/** 
- * VipsExtend:
- * @VIPS_EXTEND_BLACK: extend with black (all 0) pixels
- * @VIPS_EXTEND_COPY: copy the image edges
- * @VIPS_EXTEND_REPEAT: repeat the whole image
- * @VIPS_EXTEND_MIRROR: mirror the whole image
- * @VIPS_EXTEND_WHITE: extend with white (all bits set) pixels
- * @VIPS_EXTEND_BACKGROUND: extend with colour from the @background property
- *
- * See vips_embed(), vips_conv(), vips_affine() and so on.
- *
- * When the edges of an image are extended, you can specify
- * how you want the extension done. 
- *
- * #VIPS_EXTEND_BLACK --- new pixels are black, ie. all bits are zero. 
- *
- * #VIPS_EXTEND_COPY --- each new pixel takes the value of the nearest edge
- * pixel
- *
- * #VIPS_EXTEND_REPEAT --- the image is tiled to fill the new area
- *
- * #VIPS_EXTEND_MIRROR --- the image is reflected and tiled to reduce hash
- * edges
- *
- * #VIPS_EXTEND_WHITE --- new pixels are white, ie. all bits are set
-
- * #VIPS_EXTEND_BACKGROUND --- colour set from the @background property
- *
- * We have to specify the exact value of each enum member since we have to 
- * keep these frozen for back compat with vips7.
- *
- * See also: vips_embed().
- */
 typedef enum {
 	VIPS_EXTEND_BLACK,
 	VIPS_EXTEND_COPY,
@@ -81,39 +48,12 @@ typedef enum {
 	VIPS_EXTEND_LAST
 } VipsExtend;
 
-/** 
- * VipsDirection:
- * @VIPS_DIRECTION_HORIZONTAL: left-right 
- * @VIPS_DIRECTION_VERTICAL: top-bottom
- *
- * See vips_flip(), vips_join() and so on.
- *
- * Operations like vips_flip() need to be told whether to flip left-right or
- * top-bottom. 
- *
- * See also: vips_flip(), vips_join().
- */
 typedef enum {
 	VIPS_DIRECTION_HORIZONTAL,
 	VIPS_DIRECTION_VERTICAL,
 	VIPS_DIRECTION_LAST
 } VipsDirection;
 
-/** 
- * VipsAlign:
- * @VIPS_ALIGN_LOW: align low coordinate edge
- * @VIPS_ALIGN_CENTRE: align centre
- * @VIPS_ALIGN_HIGH: align high coordinate edge
- *
- * See vips_join() and so on.
- *
- * Operations like vips_join() need to be told whether to align images on the
- * low or high coordinate edge, or centre.
- *
- *
- *
- * See also: vips_join().
- */
 typedef enum {
 	VIPS_ALIGN_LOW,
 	VIPS_ALIGN_CENTRE,
@@ -121,19 +61,6 @@ typedef enum {
 	VIPS_ALIGN_LAST
 } VipsAlign;
 
-/** 
- * VipsAngle:
- * @VIPS_ANGLE_0: no rotate
- * @VIPS_ANGLE_90: 90 degrees anti-clockwise
- * @VIPS_ANGLE_180: 180 degree rotate
- * @VIPS_ANGLE_270: 90 degrees clockwise
- *
- * See vips_rot() and so on.
- *
- * Fixed rotate angles.
- *
- * See also: vips_rot().
- */
 typedef enum {
 	VIPS_ANGLE_0,
 	VIPS_ANGLE_90,
@@ -142,24 +69,6 @@ typedef enum {
 	VIPS_ANGLE_LAST
 } VipsAngle;
 
-/** 
- * VipsCacheStrategy:
- * @VIPS_CACHE_RANDOM: expect random access
- * @VIPS_CACHE_SEQUENTIAL: expect sequential access
- *
- * See vips_tilecache() and friends.
- *
- * Used to hint to caches about the expected access pattern. RANDOM might mean
- * LRU eviction, SEQUENTIAL might mean top-most eviction.
- *
- * See also: vips_tilecache().
- */
-typedef enum {
-	VIPS_CACHE_RANDOM,
-	VIPS_CACHE_SEQUENTIAL,
-	VIPS_CACHE_LAST
-} VipsCacheStrategy;
-
 int vips_copy( VipsImage *in, VipsImage **out, ... )
 	__attribute__((sentinel));
 int vips_tilecache( VipsImage *in, VipsImage **out, ... )
diff --git a/libvips/include/vips/enumtypes.h b/libvips/include/vips/enumtypes.h
index 4f0527c6..66393cbd 100644
--- a/libvips/include/vips/enumtypes.h
+++ b/libvips/include/vips/enumtypes.h
@@ -9,8 +9,6 @@ G_BEGIN_DECLS
 /* enumerations from "../../../libvips/include/vips/foreign.h" */
 GType vips_foreign_flags_get_type (void) G_GNUC_CONST;
 #define VIPS_TYPE_FOREIGN_FLAGS (vips_foreign_flags_get_type())
-GType vips_foreign_access_get_type (void) G_GNUC_CONST;
-#define VIPS_TYPE_FOREIGN_ACCESS (vips_foreign_access_get_type())
 GType vips_saveable_get_type (void) G_GNUC_CONST;
 #define VIPS_TYPE_SAVEABLE (vips_saveable_get_type())
 GType vips_foreign_tiff_compression_get_type (void) G_GNUC_CONST;
@@ -49,8 +47,6 @@ GType vips_align_get_type (void) G_GNUC_CONST;
 #define VIPS_TYPE_ALIGN (vips_align_get_type())
 GType vips_angle_get_type (void) G_GNUC_CONST;
 #define VIPS_TYPE_ANGLE (vips_angle_get_type())
-GType vips_cache_strategy_get_type (void) G_GNUC_CONST;
-#define VIPS_TYPE_CACHE_STRATEGY (vips_cache_strategy_get_type())
 /* enumerations from "../../../libvips/include/vips/util.h" */
 GType vips_token_get_type (void) G_GNUC_CONST;
 #define VIPS_TYPE_TOKEN (vips_token_get_type())
@@ -65,6 +61,8 @@ GType vips_band_format_get_type (void) G_GNUC_CONST;
 #define VIPS_TYPE_BAND_FORMAT (vips_band_format_get_type())
 GType vips_coding_get_type (void) G_GNUC_CONST;
 #define VIPS_TYPE_CODING (vips_coding_get_type())
+GType vips_access_get_type (void) G_GNUC_CONST;
+#define VIPS_TYPE_ACCESS (vips_access_get_type())
 /* enumerations from "../../../libvips/include/vips/colour.h" */
 GType vips_intent_get_type (void) G_GNUC_CONST;
 #define VIPS_TYPE_INTENT (vips_intent_get_type())
diff --git a/libvips/include/vips/foreign.h b/libvips/include/vips/foreign.h
index 38507dcc..b3b1e79d 100644
--- a/libvips/include/vips/foreign.h
+++ b/libvips/include/vips/foreign.h
@@ -110,12 +110,6 @@ typedef enum /*< flags >*/ {
 	(G_TYPE_INSTANCE_GET_CLASS( (obj), \
 	VIPS_TYPE_FOREIGN_LOAD, VipsForeignLoadClass ))
 
-typedef enum {
-	VIPS_FOREIGN_ACCESS_RANDOM,
-	VIPS_FOREIGN_ACCESS_SEQUENTIAL,
-	VIPS_FOREIGN_ACCESS_SEQUENTIAL_UNBUFFERED
-} VipsForeignAccess;
-
 typedef struct _VipsForeignLoad {
 	VipsForeign parent_object;
 	/*< private >*/
@@ -124,9 +118,9 @@ typedef struct _VipsForeignLoad {
 	 */
 	gboolean disc;
 
-	/* Type of access the reader requires. 
+	/* Type of access upstream wants and the loader must supply. 
 	 */
-	VipsForeignAccess access;
+	VipsAccess access;
 
 	/* Flags for this load operation.
 	 */
diff --git a/libvips/include/vips/image.h b/libvips/include/vips/image.h
index 83b06185..5ba8689b 100644
--- a/libvips/include/vips/image.h
+++ b/libvips/include/vips/image.h
@@ -47,44 +47,6 @@ extern "C" {
 #define VIPS_MAGIC_INTEL (0xb6a6f208U)
 #define VIPS_MAGIC_SPARC (0x08f2a6b6U)
 
-/** 
- * VipsDemandStyle:
- * @VIPS_DEMAND_STYLE_SMALLTILE: demand in small (typically 64x64 pixel) tiles
- * @VIPS_DEMAND_STYLE_FATSTRIP: demand in fat (typically 10 pixel high) strips
- * @VIPS_DEMAND_STYLE_THINSTRIP: demand in thin (typically 1 pixel high) strips
- * @VIPS_DEMAND_STYLE_ANY: demand geometry does not matter
- *
- * See vips_demand_hint(). Operations can hint to the VIPS image IO system about
- * the kind of demand geometry they prefer. 
- *
- * These demand styles are given below in order of increasing
- * restrictiveness.  When demanding output from a pipeline, 
- * vips_image_generate()
- * will use the most restrictive of the styles requested by the operations 
- * in the pipeline.
- *
- * #VIPS_DEMAND_STYLE_THINSTRIP --- This operation would like to output strips 
- * the width of the image and a few pels high. This is option suitable for 
- * point-to-point operations, such as those in the arithmetic package.
- *
- * This option is only efficient for cases where each output pel depends 
- * upon the pel in the corresponding position in the input image.
- *
- * #VIPS_DEMAND_STYLE_FATSTRIP --- This operation would like to output strips 
- * the width of the image and as high as possible. This option is suitable 
- * for area operations which do not violently transform coordinates, such 
- * as im_conv(). 
- *
- * #VIPS_DEMAND_STYLE_SMALLTILE --- This is the most general demand format.
- * Output is demanded in small (around 100x100 pel) sections. This style works 
- * reasonably efficiently, even for bizzare operations like 45 degree rotate.
- *
- * #VIPS_DEMAND_STYLE_ANY --- This image is not being demand-read from a disc 
- * file (even indirectly) so any demand style is OK. It's used for things like
- * im_black() where the pixels are calculated.
- *
- * See also: vips_demand_hint().
- */
 typedef enum {
 	VIPS_DEMAND_STYLE_ERROR = -1,	
 	VIPS_DEMAND_STYLE_SMALLTILE,	
@@ -108,38 +70,6 @@ typedef enum {
 	VIPS_IMAGE_PARTIAL		/* partial image */
 } VipsImageType;
 
-/**
- * VipsInterpretation: 
- * @VIPS_INTERPRETATION_MULTIBAND: generic many-band image
- * @VIPS_INTERPRETATION_B_W: some kind of single-band image
- * @VIPS_INTERPRETATION_HISTOGRAM: a 1D image, eg. histogram or lookup table
- * @VIPS_INTERPRETATION_FOURIER: image is in fourier space
- * @VIPS_INTERPRETATION_XYZ: the first three bands are CIE XYZ 
- * @VIPS_INTERPRETATION_LAB: pixels are in CIE Lab space
- * @VIPS_INTERPRETATION_CMYK: the first four bands are in CMYK space
- * @VIPS_INTERPRETATION_LABQ: implies #VIPS_CODING_LABQ
- * @VIPS_INTERPRETATION_RGB: generic RGB space
- * @VIPS_INTERPRETATION_CMC: a uniform colourspace based on CMC(1:1)
- * @VIPS_INTERPRETATION_LCH: pixels are in CIE LCh space
- * @VIPS_INTERPRETATION_LABS: CIE LAB coded as three signed 16-bit values
- * @VIPS_INTERPRETATION_sRGB: pixels are sRGB
- * @VIPS_INTERPRETATION_scRGB: pixels are scRGB
- * @VIPS_INTERPRETATION_YXY: pixels are CIE Yxy
- * @VIPS_INTERPRETATION_RGB16: generic 16-bit RGB
- * @VIPS_INTERPRETATION_GREY16: generic 16-bit mono
- * @VIPS_INTERPRETATION_MATRIX: a matrix
- *
- * How the values in an image should be interpreted. For example, a
- * three-band float image of type #VIPS_INTERPRETATION_LAB should have its 
- * pixels interpreted as coordinates in CIE Lab space.
- *
- * These values are set by operations as hints to user-interfaces built on top 
- * of VIPS to help them show images to the user in a meaningful way. 
- * Operations do not use these values to decide their action.
- *
- * The gaps in the numbering are historical and must be maintained. Allocate 
- * new numbers from the end.
- */
 typedef enum {
 	VIPS_INTERPRETATION_ERROR = -1,
 	VIPS_INTERPRETATION_MULTIBAND = 0,
@@ -162,25 +92,6 @@ typedef enum {
 	VIPS_INTERPRETATION_scRGB = 28
 } VipsInterpretation;
 
-/**
- * VipsBandFormat: 
- * @VIPS_FORMAT_NOTSET: invalid setting
- * @VIPS_FORMAT_UCHAR: unsigned char format
- * @VIPS_FORMAT_CHAR: char format
- * @VIPS_FORMAT_USHORT: unsigned short format
- * @VIPS_FORMAT_SHORT: short format
- * @VIPS_FORMAT_UINT: unsigned int format
- * @VIPS_FORMAT_INT: int format
- * @VIPS_FORMAT_FLOAT: float format
- * @VIPS_FORMAT_COMPLEX: complex (two floats) format
- * @VIPS_FORMAT_DOUBLE: double float format
- * @VIPS_FORMAT_DPCOMPLEX: double complex (two double) format
- *
- * The format used for each band element. 
- *
- * Each corresponnds to a native C type for the current machine. For example,
- * #VIPS_FORMAT_USHORT is <type>unsigned short</type>.
- */
 typedef enum {
 	VIPS_FORMAT_NOTSET = -1,
 	VIPS_FORMAT_UCHAR = 0,
@@ -196,21 +107,6 @@ typedef enum {
 	VIPS_FORMAT_LAST = 10
 } VipsBandFormat;
 
-/**
- * VipsCoding: 
- * @VIPS_CODING_NONE: pixels are not coded
- * @VIPS_CODING_LABQ: pixels encode 3 float CIELAB values as 4 uchar
- * @VIPS_CODING_RAD: pixels encode 3 float RGB as 4 uchar (Radiance coding)
- *
- * How pixels are coded. 
- *
- * Normally, pixels are uncoded and can be manipulated as you would expect.
- * However some file formats code pixels for compression, and sometimes it's
- * useful to be able to manipulate images in the coded format.
- *
- * The gaps in the numbering are historical and must be maintained. Allocate 
- * new numbers from the end.
- */
 typedef enum {
 	VIPS_CODING_ERROR = -1,
 	VIPS_CODING_NONE = 0,
@@ -219,6 +115,13 @@ typedef enum {
 	VIPS_CODING_LAST = 7
 } VipsCoding;
 
+typedef enum {
+	VIPS_ACCESS_RANDOM,
+	VIPS_ACCESS_SEQUENTIAL,
+	VIPS_ACCESS_SEQUENTIAL_UNBUFFERED,
+	VIPS_ACCESS_LAST
+} VipsAccess;
+
 /* Struct we keep a record of execution time in. Passed to eval signal so
  * it can assess progress.
  */
diff --git a/libvips/include/vips/operation.h b/libvips/include/vips/operation.h
index c10ba8eb..a03eb24b 100644
--- a/libvips/include/vips/operation.h
+++ b/libvips/include/vips/operation.h
@@ -37,25 +37,11 @@ extern "C" {
 
 #include <vips/vips.h>
 
-/** 
- * VipsOperationFlags:
- * @VIPS_OPERATION_NONE: no flags
- * @VIPS_OPERATION_SEQUENTIAL: can work sequentially
- * @VIPS_OPERATION_NOCACHE: must not be cached
- *
- * Flags we associate with an operation.
- *
- * @VIPS_OPERATION_SEQUENTIAL means that the operation works like vips_copy:
- * it can happily process images top-to-bottom with only small non-local
- * references.
- *
- * @VIPS_OPERATION_NOCACHE means that the operation must not be cached by
- * vips. 
- */
 typedef enum /*< flags >*/ {
 	VIPS_OPERATION_NONE = 0,
 	VIPS_OPERATION_SEQUENTIAL = 1,
-	VIPS_OPERATION_NOCACHE = 2
+	VIPS_OPERATION_SEQUENTIAL_UNBUFFERED = 2,
+	VIPS_OPERATION_NOCACHE = 3
 } VipsOperationFlags;
 
 #define VIPS_TYPE_OPERATION (vips_operation_get_type())
diff --git a/libvips/iofuncs/enumtypes.c b/libvips/iofuncs/enumtypes.c
index 2f534e12..c343eaaa 100644
--- a/libvips/iofuncs/enumtypes.c
+++ b/libvips/iofuncs/enumtypes.c
@@ -26,24 +26,6 @@ vips_foreign_flags_get_type( void )
 	return( etype );
 }
 GType
-vips_foreign_access_get_type( void )
-{
-	static GType etype = 0;
-
-	if( etype == 0 ) {
-		static const GEnumValue values[] = {
-			{VIPS_FOREIGN_ACCESS_RANDOM, "VIPS_FOREIGN_ACCESS_RANDOM", "random"},
-			{VIPS_FOREIGN_ACCESS_SEQUENTIAL, "VIPS_FOREIGN_ACCESS_SEQUENTIAL", "sequential"},
-			{VIPS_FOREIGN_ACCESS_SEQUENTIAL_UNBUFFERED, "VIPS_FOREIGN_ACCESS_SEQUENTIAL_UNBUFFERED", "sequential-unbuffered"},
-			{0, NULL, NULL}
-		};
-		
-		etype = g_enum_register_static( "VipsForeignAccess", values );
-	}
-
-	return( etype );
-}
-GType
 vips_saveable_get_type( void )
 {
 	static GType etype = 0;
@@ -241,24 +223,6 @@ vips_angle_get_type( void )
 
 	return( etype );
 }
-GType
-vips_cache_strategy_get_type( void )
-{
-	static GType etype = 0;
-
-	if( etype == 0 ) {
-		static const GEnumValue values[] = {
-			{VIPS_CACHE_RANDOM, "VIPS_CACHE_RANDOM", "random"},
-			{VIPS_CACHE_SEQUENTIAL, "VIPS_CACHE_SEQUENTIAL", "sequential"},
-			{VIPS_CACHE_LAST, "VIPS_CACHE_LAST", "last"},
-			{0, NULL, NULL}
-		};
-		
-		etype = g_enum_register_static( "VipsCacheStrategy", values );
-	}
-
-	return( etype );
-}
 /* enumerations from "../../libvips/include/vips/arithmetic.h" */
 GType
 vips_operation_math_get_type( void )
@@ -567,6 +531,25 @@ vips_coding_get_type( void )
 
 	return( etype );
 }
+GType
+vips_access_get_type( void )
+{
+	static GType etype = 0;
+
+	if( etype == 0 ) {
+		static const GEnumValue values[] = {
+			{VIPS_ACCESS_RANDOM, "VIPS_ACCESS_RANDOM", "random"},
+			{VIPS_ACCESS_SEQUENTIAL, "VIPS_ACCESS_SEQUENTIAL", "sequential"},
+			{VIPS_ACCESS_SEQUENTIAL_UNBUFFERED, "VIPS_ACCESS_SEQUENTIAL_UNBUFFERED", "sequential-unbuffered"},
+			{VIPS_ACCESS_LAST, "VIPS_ACCESS_LAST", "last"},
+			{0, NULL, NULL}
+		};
+		
+		etype = g_enum_register_static( "VipsAccess", values );
+	}
+
+	return( etype );
+}
 /* enumerations from "../../libvips/include/vips/operation.h" */
 GType
 vips_operation_flags_get_type( void )
@@ -577,6 +560,7 @@ vips_operation_flags_get_type( void )
 		static const GFlagsValue values[] = {
 			{VIPS_OPERATION_NONE, "VIPS_OPERATION_NONE", "none"},
 			{VIPS_OPERATION_SEQUENTIAL, "VIPS_OPERATION_SEQUENTIAL", "sequential"},
+			{VIPS_OPERATION_SEQUENTIAL_UNBUFFERED, "VIPS_OPERATION_SEQUENTIAL_UNBUFFERED", "sequential-unbuffered"},
 			{VIPS_OPERATION_NOCACHE, "VIPS_OPERATION_NOCACHE", "nocache"},
 			{0, NULL, NULL}
 		};
diff --git a/libvips/iofuncs/image.c b/libvips/iofuncs/image.c
index 6c84e91b..386415b1 100644
--- a/libvips/iofuncs/image.c
+++ b/libvips/iofuncs/image.c
@@ -80,6 +80,132 @@
  * The first four bytes of a VIPS file in SPARC byte ordering.
  */
 
+/** 
+ * VipsAccess:
+ * @VIPS_ACCESS_RANDOM: can read anywhere
+ * @VIPS_ACCESS_SEQUENTIAL: top-to-bottom reading only, but with a small buffer
+ * @VIPS_ACCESS_SEQUENTIAL_UNBUFFERED: top-to-bottom reading only
+ *
+ * The type of access an operation has to supply. See vips_tilecache()
+ * and #VipsForeign. 
+ *
+ * @VIPS_ACCESS_RANDOM means requests can come in any order. 
+ *
+ * @VIPS_ACCESS_SEQUENTIAL means requests will be top-to-bottom, but with some
+ * amount of buffering behind the read point for small non-local accesses. 
+ *
+ * @VIPS_ACCESS_SEQUENTIAL_UNBUFFERED means requests will be strictly
+ * top-to-bottom with no read-behind. This can save some memory. 
+ */
+
+/** 
+ * VipsDemandStyle:
+ * @VIPS_DEMAND_STYLE_SMALLTILE: demand in small (typically 64x64 pixel) tiles
+ * @VIPS_DEMAND_STYLE_FATSTRIP: demand in fat (typically 10 pixel high) strips
+ * @VIPS_DEMAND_STYLE_THINSTRIP: demand in thin (typically 1 pixel high) strips
+ * @VIPS_DEMAND_STYLE_ANY: demand geometry does not matter
+ *
+ * See vips_demand_hint(). Operations can hint to the VIPS image IO system about
+ * the kind of demand geometry they prefer. 
+ *
+ * These demand styles are given below in order of increasing
+ * restrictiveness.  When demanding output from a pipeline, 
+ * vips_image_generate()
+ * will use the most restrictive of the styles requested by the operations 
+ * in the pipeline.
+ *
+ * #VIPS_DEMAND_STYLE_THINSTRIP --- This operation would like to output strips 
+ * the width of the image and a few pels high. This is option suitable for 
+ * point-to-point operations, such as those in the arithmetic package.
+ *
+ * This option is only efficient for cases where each output pel depends 
+ * upon the pel in the corresponding position in the input image.
+ *
+ * #VIPS_DEMAND_STYLE_FATSTRIP --- This operation would like to output strips 
+ * the width of the image and as high as possible. This option is suitable 
+ * for area operations which do not violently transform coordinates, such 
+ * as im_conv(). 
+ *
+ * #VIPS_DEMAND_STYLE_SMALLTILE --- This is the most general demand format.
+ * Output is demanded in small (around 100x100 pel) sections. This style works 
+ * reasonably efficiently, even for bizzare operations like 45 degree rotate.
+ *
+ * #VIPS_DEMAND_STYLE_ANY --- This image is not being demand-read from a disc 
+ * file (even indirectly) so any demand style is OK. It's used for things like
+ * im_black() where the pixels are calculated.
+ *
+ * See also: vips_demand_hint().
+ */
+
+/**
+ * VipsInterpretation: 
+ * @VIPS_INTERPRETATION_MULTIBAND: generic many-band image
+ * @VIPS_INTERPRETATION_B_W: some kind of single-band image
+ * @VIPS_INTERPRETATION_HISTOGRAM: a 1D image, eg. histogram or lookup table
+ * @VIPS_INTERPRETATION_FOURIER: image is in fourier space
+ * @VIPS_INTERPRETATION_XYZ: the first three bands are CIE XYZ 
+ * @VIPS_INTERPRETATION_LAB: pixels are in CIE Lab space
+ * @VIPS_INTERPRETATION_CMYK: the first four bands are in CMYK space
+ * @VIPS_INTERPRETATION_LABQ: implies #VIPS_CODING_LABQ
+ * @VIPS_INTERPRETATION_RGB: generic RGB space
+ * @VIPS_INTERPRETATION_CMC: a uniform colourspace based on CMC(1:1)
+ * @VIPS_INTERPRETATION_LCH: pixels are in CIE LCh space
+ * @VIPS_INTERPRETATION_LABS: CIE LAB coded as three signed 16-bit values
+ * @VIPS_INTERPRETATION_sRGB: pixels are sRGB
+ * @VIPS_INTERPRETATION_scRGB: pixels are scRGB
+ * @VIPS_INTERPRETATION_YXY: pixels are CIE Yxy
+ * @VIPS_INTERPRETATION_RGB16: generic 16-bit RGB
+ * @VIPS_INTERPRETATION_GREY16: generic 16-bit mono
+ * @VIPS_INTERPRETATION_MATRIX: a matrix
+ *
+ * How the values in an image should be interpreted. For example, a
+ * three-band float image of type #VIPS_INTERPRETATION_LAB should have its 
+ * pixels interpreted as coordinates in CIE Lab space.
+ *
+ * These values are set by operations as hints to user-interfaces built on top 
+ * of VIPS to help them show images to the user in a meaningful way. 
+ * Operations do not use these values to decide their action.
+ *
+ * The gaps in the numbering are historical and must be maintained. Allocate 
+ * new numbers from the end.
+ */
+
+/**
+ * VipsBandFormat: 
+ * @VIPS_FORMAT_NOTSET: invalid setting
+ * @VIPS_FORMAT_UCHAR: unsigned char format
+ * @VIPS_FORMAT_CHAR: char format
+ * @VIPS_FORMAT_USHORT: unsigned short format
+ * @VIPS_FORMAT_SHORT: short format
+ * @VIPS_FORMAT_UINT: unsigned int format
+ * @VIPS_FORMAT_INT: int format
+ * @VIPS_FORMAT_FLOAT: float format
+ * @VIPS_FORMAT_COMPLEX: complex (two floats) format
+ * @VIPS_FORMAT_DOUBLE: double float format
+ * @VIPS_FORMAT_DPCOMPLEX: double complex (two double) format
+ *
+ * The format used for each band element. 
+ *
+ * Each corresponnds to a native C type for the current machine. For example,
+ * #VIPS_FORMAT_USHORT is <type>unsigned short</type>.
+ */
+
+/**
+ * VipsCoding: 
+ * @VIPS_CODING_NONE: pixels are not coded
+ * @VIPS_CODING_LABQ: pixels encode 3 float CIELAB values as 4 uchar
+ * @VIPS_CODING_RAD: pixels encode 3 float RGB as 4 uchar (Radiance coding)
+ *
+ * How pixels are coded. 
+ *
+ * Normally, pixels are uncoded and can be manipulated as you would expect.
+ * However some file formats code pixels for compression, and sometimes it's
+ * useful to be able to manipulate images in the coded format.
+ *
+ * The gaps in the numbering are historical and must be maintained. Allocate 
+ * new numbers from the end.
+ */
+
 /** 
  * VipsProgress:
  * @run: Time we have been running 
diff --git a/libvips/iofuncs/object.c b/libvips/iofuncs/object.c
index 722f57b7..88fdecbb 100644
--- a/libvips/iofuncs/object.c
+++ b/libvips/iofuncs/object.c
@@ -1519,6 +1519,7 @@ vips_object_set_argument_from_string( VipsObject *object,
 	if( g_type_is_a( otype, VIPS_TYPE_IMAGE ) ) { 
 		VipsImage *out;
 		VipsOperationFlags flags;
+		VipsAccess access;
 
 		flags = 0;
 		if( VIPS_IS_OPERATION( object ) )
@@ -1533,17 +1534,17 @@ vips_object_set_argument_from_string( VipsObject *object,
 		/* Read the filename. vips_foreign_load_options()
 		 * handles embedded options.
 		 */
-		if( flags & VIPS_OPERATION_SEQUENTIAL ) {
-			if( vips_foreign_load_options( value, &out, 
-				"access", VIPS_FOREIGN_ACCESS_SEQUENTIAL,
-				NULL ) )
-				return( -1 );
-		}
-		else {
-			if( vips_foreign_load_options( value, &out, 
-				NULL ) )
-				return( -1 );
-		}
+		if( flags & VIPS_OPERATION_SEQUENTIAL_UNBUFFERED ) 
+			access = VIPS_ACCESS_SEQUENTIAL_UNBUFFERED;
+		else if( flags & VIPS_OPERATION_SEQUENTIAL ) 
+			access = VIPS_ACCESS_SEQUENTIAL;
+		else
+			access = VIPS_ACCESS_RANDOM; 
+
+		if( vips_foreign_load_options( value, &out, 
+			"access", access,
+			NULL ) )
+			return( -1 );
 
 		g_value_init( &gvalue, VIPS_TYPE_IMAGE );
 		g_value_set_object( &gvalue, out );
diff --git a/libvips/iofuncs/operation.c b/libvips/iofuncs/operation.c
index 837b7ad2..6deb4db0 100644
--- a/libvips/iofuncs/operation.c
+++ b/libvips/iofuncs/operation.c
@@ -65,6 +65,26 @@
  *
  */
 
+/** 
+ * VipsOperationFlags:
+ * @VIPS_OPERATION_NONE: no flags
+ * @VIPS_OPERATION_SEQUENTIAL: can work sequentially
+ * @VIPS_OPERATION_NOCACHE: must not be cached
+ *
+ * Flags we associate with an operation.
+ *
+ * @VIPS_OPERATION_SEQUENTIAL means that the operation works like vips_conv():
+ * it can happily process images top-to-bottom with only small non-local
+ * references.
+ *
+ * @VIPS_OPERATION_SEQUENTIAL_UNBUFFERED means that the operation works like 
+ * vips_copy(): it can happily process images top-to-bottom and makes no 
+ * non-local references. 
+ *
+ * @VIPS_OPERATION_NOCACHE means that the operation must not be cached by
+ * vips. 
+ */
+
 /* Abstract base class for operations.
  */