add thumbnail_stream

this works:

	$ cat k2.jpg | vips thumbnail_stream [descriptor=0] x.jpg 200
	$ vipsheader x.jpg
	temp-0: 141x200 uchar, 3 bands, srgb, jpegload

libvips/include/vips/resample.h

@@ -79,6 +79,9 @@ int vips_thumbnail_buffer( void *buf, size_t len, VipsImage **out,
 	__attribute__((sentinel));
 int vips_thumbnail_image( VipsImage *in, VipsImage **out, int width, ... )
 	__attribute__((sentinel));
+int vips_thumbnail_stream( VipsStreamInput *input, VipsImage **out, 
+	int width, ... )
+	__attribute__((sentinel));
 
 int vips_similarity( VipsImage *in, VipsImage **out, ... )
 	__attribute__((sentinel));

libvips/include/vips/stream.h

@@ -171,6 +171,7 @@ VipsStreamInput *vips_stream_input_new_from_filename( const char *filename );
 VipsStreamInput *vips_stream_input_new_from_blob( VipsBlob *blob );
 VipsStreamInput *vips_stream_input_new_from_memory( const void *data, 
 	size_t size );
+VipsStreamInput *vips_stream_input_new_from_options( const char *options );
 
 ssize_t vips_stream_input_read( VipsStreamInput *input, 
 	unsigned char *data, size_t length );

libvips/iofuncs/object.c

@@ -1889,18 +1889,11 @@ vips_object_set_argument_from_string( VipsObject *object,
 		char filename[VIPS_PATH_MAX];
 		char option_string[VIPS_PATH_MAX];
 
-		if( !value ) {
-			vips_object_no_value( object, name );
-			return( -1 );
-		}
-
 		flags = 0;
 		if( VIPS_IS_OPERATION( object ) )
 			flags = vips_operation_get_flags( 
 				VIPS_OPERATION( object ) );
 
-		/* Read the filename. 
-		 */
 		if( flags & 
 			(VIPS_OPERATION_SEQUENTIAL_UNBUFFERED | 
 			 VIPS_OPERATION_SEQUENTIAL) ) 
@@ -1908,6 +1901,10 @@ vips_object_set_argument_from_string( VipsObject *object,
 		else
 			access = VIPS_ACCESS_RANDOM; 
 
+		if( !value ) {
+			vips_object_no_value( object, name );
+			return( -1 );
+		}
 		vips__filename_split8( value, filename, option_string );
 
 		if( strcmp( "stdin", filename ) == 0 ) {
@@ -1940,6 +1937,25 @@ vips_object_set_argument_from_string( VipsObject *object,
 		 */
 		g_object_unref( out );
 	}
+	else if( g_type_is_a( otype, VIPS_TYPE_STREAM_INPUT ) ) { 
+		VipsStreamInput *input;
+
+		if( !value ) {
+			vips_object_no_value( object, name );
+			return( -1 );
+		}
+
+		if( !(input = vips_stream_input_new_from_options( value )) )
+			return( -1 );
+	
+		g_value_init( &gvalue, VIPS_TYPE_STREAM_INPUT );
+		g_value_set_object( &gvalue, input );
+
+		/* Setting gvalue will have upped @out's count again,
+		 * go back to 1 so that gvalue has the only ref.
+		 */
+		g_object_unref( input );
+	}
 	else if( g_type_is_a( otype, VIPS_TYPE_ARRAY_IMAGE ) ) { 
 		/* We have to have a special case for this, we can't just rely
 		 * on transform_g_string_array_image(), since we need to be

libvips/iofuncs/operation.c

@@ -1245,7 +1245,8 @@ typedef struct _VipsCall {
 static const char *
 vips_call_get_arg( VipsCall *call, int i )
 {
-	if( i < 0 || i >= call->argc ) {
+	if( i < 0 || 
+		i >= call->argc ) {
 		vips_error( VIPS_OBJECT_GET_CLASS( call->operation )->nickname, 
 			"%s", _( "too few arguments" ) );
 		return( NULL );

libvips/iofuncs/stream.c

@@ -33,6 +33,7 @@
 
 /* TODO
  *
+ * - minimise support, and reenable jpg test_descriptors
  * - filename encoding
  * - memory output
  * - add mmapable descriptors
@@ -322,7 +323,7 @@ vips_stream_input_class_init( VipsStreamInputClass *class )
 	gobject_class->set_property = vips_object_set_property;
 	gobject_class->get_property = vips_object_get_property;
 
-	object_class->nickname = "input";
+	object_class->nickname = "stream_input";
 	object_class->description = _( "input stream" );
 
 	object_class->build = vips_stream_input_build;
@@ -416,67 +417,84 @@ vips_stream_input_new_from_filename( const char *filename )
  *
  * Create a stream attached to an area of memory. 
  *
- * #VipsStream s start out empty, you need to call 
- * vips_stream_input_refill() to fill them with bytes.
- *
- * See also: vips_stream_input_refill().
- *
  * Returns: a new #VipsStream
  */
 VipsStreamInput *
 vips_stream_input_new_from_blob( VipsBlob *blob )
 {
-	VipsStreamInput *stream;
+	VipsStreamInput *input;
 
 	VIPS_DEBUG_MSG( "vips_stream_input_new_from_blob: %p\n", blob ); 
 
-	stream = VIPS_STREAM_INPUT( 
+	input = VIPS_STREAM_INPUT( 
 		g_object_new( VIPS_TYPE_STREAM_INPUT, 
 			"blob", blob,
 			NULL ) );
 
-	if( vips_object_build( VIPS_OBJECT( stream ) ) ) {
+	if( vips_object_build( VIPS_OBJECT( input ) ) ) {
-		VIPS_UNREF( stream );
+		VIPS_UNREF( input );
 		return( NULL );
 	}
 
-	return( stream ); 
+	return( input ); 
 }
 
 /**
  * vips_stream_input_new_from_memory:
- * @buf: memory area to load
+ * @data: memory area to load
- * @len: size of memory area
+ * @length: size of memory area
  *
  * Create a stream attached to an area of memory. 
  *
- * You must not free @buf while the stream is active. 
+ * You must not free @data while the stream is active. 
- *
- * #VipsStream s start out empty, you need to call 
- * vips_stream_input_refill() to fill them with bytes.
- *
- * See also: vips_stream_input_refill().
  *
  * Returns: a new #VipsStream
  */
 VipsStreamInput *
-vips_stream_input_new_from_memory( const void *data, size_t size )
+vips_stream_input_new_from_memory( const void *data, size_t length )
 {
-	VipsStreamInput *stream;
+	VipsStreamInput *input;
 	VipsBlob *blob;
 
-	VIPS_DEBUG_MSG( "vips_stream_input_new_from_buffer: %p, size = %zd\n", 
+	VIPS_DEBUG_MSG( "vips_stream_input_new_from_buffer: "
-		data, size ); 
+		"%p, length = %zd\n", data, length ); 
 
 	/* We don't take a copy of the data or free it.
 	 */
-	blob = vips_blob_new( NULL, data, size );
+	blob = vips_blob_new( NULL, data, length );
 
-	stream = vips_stream_input_new_from_blob( blob ); 
+	input = vips_stream_input_new_from_blob( blob ); 
 
 	vips_area_unref( VIPS_AREA( blob ) );
 
-	return( stream ); 
+	return( input ); 
+}
+
+/**
+ * vips_stream_input_new_from_options:
+ * @options: option string
+ *
+ * Create a stream from an option string.
+ *
+ * Returns: a new #VipsStream
+ */
+VipsStreamInput *
+vips_stream_input_new_from_options( const char *options )
+{
+	VipsStreamInput *input;
+
+	VIPS_DEBUG_MSG( "vips_stream_input_new_from_options: %s\n", options ); 
+
+	input = VIPS_STREAM_INPUT( 
+		g_object_new( VIPS_TYPE_STREAM_INPUT, NULL ) );
+
+	if( vips_object_set_from_string( VIPS_OBJECT( input ), options ) ||
+		vips_object_build( VIPS_OBJECT( input ) ) ) {
+		VIPS_UNREF( input );
+		return( NULL );
+	}
+
+	return( input ); 
 }
 
 ssize_t
@@ -696,7 +714,7 @@ vips_stream_output_class_init( VipsStreamOutputClass *class )
 	gobject_class->set_property = vips_object_set_property;
 	gobject_class->get_property = vips_object_get_property;
 
-	object_class->nickname = "output";
+	object_class->nickname = "stream_output";
 	object_class->description = _( "output stream" );
 
 	object_class->build = vips_stream_output_build;
@@ -706,7 +724,7 @@ vips_stream_output_class_init( VipsStreamOutputClass *class )
 	/* SET_ALWAYS means that blob is set by C and the obj system is not
 	 * involved in creation or destruction. It can be read at any time.
 	 */
-	VIPS_ARG_BOXED( class, "blob", 1, 
+	VIPS_ARG_BOXED( class, "blob", 3, 
 		_( "Blob" ),
 		_( "Blob to save to" ),
 		VIPS_ARGUMENT_SET_ALWAYS, 

libvips/resample/resample.c

@@ -157,6 +157,7 @@ vips_resample_operation_init( void )
 	extern GType vips_thumbnail_file_get_type( void ); 
 	extern GType vips_thumbnail_buffer_get_type( void ); 
 	extern GType vips_thumbnail_image_get_type( void ); 
+	extern GType vips_thumbnail_stream_get_type( void ); 
 	extern GType vips_mapim_get_type( void ); 
 	extern GType vips_shrink_get_type( void ); 
 	extern GType vips_shrinkh_get_type( void ); 
@@ -173,6 +174,7 @@ vips_resample_operation_init( void )
 	vips_thumbnail_file_get_type(); 
 	vips_thumbnail_buffer_get_type(); 
 	vips_thumbnail_image_get_type(); 
+	vips_thumbnail_stream_get_type(); 
 	vips_mapim_get_type(); 
 	vips_shrink_get_type(); 
 	vips_shrinkh_get_type(); 

libvips/resample/thumbnail.c

@@ -26,6 +26,8 @@
  *	- prevent over-pre-shrink in thumbnail
  * 30/9/19
  * 	- smarter heif thumbnail selection
+ * 12/10/19
+ * 	- add thumbnail_stream
  */
 
 /*
@@ -1249,6 +1251,175 @@ vips_thumbnail_buffer( void *buf, size_t len, VipsImage **out, int width, ... )
 	return( result );
 }
 
+typedef struct _VipsThumbnailStream {
+	VipsThumbnail parent_object;
+
+	VipsStreamInput *input;
+	char *option_string;
+} VipsThumbnailStream;
+
+typedef VipsThumbnailClass VipsThumbnailStreamClass;
+
+G_DEFINE_TYPE( VipsThumbnailStream, vips_thumbnail_stream, 
+	vips_thumbnail_get_type() );
+
+/* Get the info from a stream.
+ */
+static int
+vips_thumbnail_stream_get_info( VipsThumbnail *thumbnail )
+{
+	VipsThumbnailStream *stream = (VipsThumbnailStream *) thumbnail;
+
+	VipsImage *image;
+
+	g_info( "thumbnailing stream" ); 
+
+	if( !(thumbnail->loader = vips_foreign_find_load_stream( 
+			stream->input )) ||
+		!(image = vips_image_new_from_stream( stream->input, 
+			stream->option_string, NULL )) )
+		return( -1 );
+
+	vips_thumbnail_read_header( thumbnail, image );
+
+	g_object_unref( image );
+
+	return( 0 );
+}
+
+/* Open an image, scaling as appropriate. 
+ */
+static VipsImage *
+vips_thumbnail_stream_open( VipsThumbnail *thumbnail, double factor )
+{
+	VipsThumbnailStream *stream = (VipsThumbnailStream *) thumbnail;
+
+	if( vips_isprefix( "VipsForeignLoadJpeg", thumbnail->loader ) ) {
+		return( vips_image_new_from_stream( 
+			stream->input, 
+			stream->option_string,
+			"access", VIPS_ACCESS_SEQUENTIAL,
+			"shrink", (int) factor,
+			NULL ) );
+	}
+	else if( vips_isprefix( "VipsForeignLoadOpenslide", 
+		thumbnail->loader ) ) {
+		return( vips_image_new_from_stream( 
+			stream->input, 
+			stream->option_string,
+			"access", VIPS_ACCESS_SEQUENTIAL,
+			"level", (int) factor,
+			NULL ) );
+	}
+	else if( vips_isprefix( "VipsForeignLoadPdf", thumbnail->loader ) ||
+		vips_isprefix( "VipsForeignLoadSvg", thumbnail->loader ) ||
+		vips_isprefix( "VipsForeignLoadWebp", thumbnail->loader ) ) {
+		return( vips_image_new_from_stream( 
+			stream->input, 
+			stream->option_string,
+			"access", VIPS_ACCESS_SEQUENTIAL,
+			"scale", 1.0 / factor,
+			NULL ) );
+	}
+	else if( vips_isprefix( "VipsForeignLoadTiff", thumbnail->loader ) ) {
+		return( vips_image_new_from_stream( 
+			stream->input, 
+			stream->option_string,
+			"access", VIPS_ACCESS_SEQUENTIAL,
+			"page", (int) factor,
+			NULL ) );
+	}
+	else if( vips_isprefix( "VipsForeignLoadHeif", thumbnail->loader ) ) {
+		return( vips_image_new_from_stream( 
+			stream->input, 
+			stream->option_string,
+			"access", VIPS_ACCESS_SEQUENTIAL,
+			"thumbnail", (int) factor,
+			NULL ) );
+	}
+	else {
+		return( vips_image_new_from_stream( 
+			stream->input, 
+			stream->option_string,
+			"access", VIPS_ACCESS_SEQUENTIAL,
+			NULL ) );
+	}
+}
+
+static void
+vips_thumbnail_stream_class_init( VipsThumbnailClass *class )
+{
+	GObjectClass *gobject_class = G_OBJECT_CLASS( class );
+	VipsObjectClass *vobject_class = VIPS_OBJECT_CLASS( class );
+	VipsThumbnailClass *thumbnail_class = VIPS_THUMBNAIL_CLASS( class );
+
+	gobject_class->set_property = vips_object_set_property;
+	gobject_class->get_property = vips_object_get_property;
+
+	vobject_class->nickname = "thumbnail_stream";
+	vobject_class->description = _( "generate thumbnail from stream" );
+
+	thumbnail_class->get_info = vips_thumbnail_stream_get_info;
+	thumbnail_class->open = vips_thumbnail_stream_open;
+
+	VIPS_ARG_OBJECT( class, "input", 1,
+		_( "Input" ),
+		_( "Stream to load from" ),
+		VIPS_ARGUMENT_REQUIRED_INPUT, 
+		G_STRUCT_OFFSET( VipsThumbnailStream, input ),
+		VIPS_TYPE_STREAM_INPUT );
+
+	VIPS_ARG_STRING( class, "option_string", 20,
+		_( "Extra options" ),
+		_( "Options that are passed on to the underlying loader" ),
+		VIPS_ARGUMENT_OPTIONAL_INPUT,
+		G_STRUCT_OFFSET( VipsThumbnailStream, option_string ),
+		"" );
+
+}
+
+static void
+vips_thumbnail_stream_init( VipsThumbnailStream *stream )
+{
+}
+
+/**
+ * vips_thumbnail_stream:
+ * @input: stream to thumbnail
+ * @out: (out): output image
+ * @width: target width in pixels
+ * @...: %NULL-terminated list of optional named arguments
+ *
+ * Optional arguments:
+ *
+ * * @height: %gint, target height in pixels
+ * * @size: #VipsSize, upsize, downsize, both or force
+ * * @no_rotate: %gboolean, don't rotate upright using orientation tag
+ * * @crop: #VipsInteresting, shrink and crop to fill target
+ * * @linear: %gboolean, perform shrink in linear light
+ * * @import_profile: %gchararray, fallback import ICC profile
+ * * @export_profile: %gchararray, export ICC profile
+ * * @intent: #VipsIntent, rendering intent
+ *
+ * Exacty as vips_thumbnail(), but read from a stream. 
+ *
+ * See also: vips_thumbnail().
+ *
+ * Returns: 0 on success, -1 on error.
+ */
+int
+vips_thumbnail_stream( VipsStreamInput *input, VipsImage **out, int width, ... )
+{
+	va_list ap;
+	int result;
+
+	va_start( ap, width );
+	result = vips_call_split( "thumbnail_stream", ap, input, out, width );
+	va_end( ap );
+
+	return( result );
+}
+
 typedef struct _VipsThumbnailImage {
 	VipsThumbnail parent_object;