allow symbolic names for flags

you can now use numbers or names for GFlags values, eg.:

$ vips copy 50020484-00001.png x.png[filter=avg]
$ vips copy 50020484-00001.png x.png[filter=64]

was numbers only before

ChangeLog

@@ -18,6 +18,7 @@
 - add support for vips8 plugins
 - added "autorotate" option to jpeg load
 - added autorot operator
+- added @filter option to pngsave (Lovell)
 
 8/10/14 started 7.40.11
 - rework extra band handling for colour functions

libvips/foreign/foreign.c

@@ -2487,7 +2487,7 @@ vips_pngload_buffer( void *buf, size_t len, VipsImage **out, ... )
  * @compression: compression level
  * @interlace: interlace image
  * @profile: ICC profile to embed
- * @filter: libpng row filter flag(s)
+ * @filter: #VipsForeignPngFilter row filter flag(s)
  *
  * Write a VIPS image to a file as PNG.
  *
@@ -2507,7 +2507,8 @@ vips_pngload_buffer( void *buf, size_t len, VipsImage **out, ... )
  * contains an ICC profile named VIPS_META_ICC_NAME ("icc-profile-data"), the
  * profile from the VIPS header will be attached.
  *
- * Use @filter to specify one or more filters (instead of adaptive filtering).
+ * Use @filter to specify one or more filters (instead of adaptive filtering),
+ * see #VipsForeignPngFilter. 
  *
  * The image is automatically converted to RGB, RGBA, Monochrome or Mono +
  * alpha before saving. Images with more than one byte per band element are

libvips/foreign/vipspng.c

@@ -50,6 +50,8 @@
  * 	- more robust error handling from libpng
  * 9/8/14
  * 	- don't check profiles, helps with libpng >=1.6.11
+ * 27/10/14 Lovell
+ * 	- add @filter option 
  */
 
 /*

libvips/include/vips/foreign.h

@@ -438,12 +438,12 @@ int vips_magickload( const char *filename, VipsImage **out, ... )
 
 /**
  * VipsForeignPngFilter:
- * @VIPS_FOREIGN_PNG_FILTER_NONE
- * @VIPS_FOREIGN_PNG_FILTER_SUB
- * @VIPS_FOREIGN_PNG_FILTER_UP
- * @VIPS_FOREIGN_PNG_FILTER_AVG
- * @VIPS_FOREIGN_PNG_FILTER_PAETH
- * @VIPS_FOREIGN_PNG_FILTER_ALL
+ * @VIPS_FOREIGN_PNG_FILTER_NONE: no filtering
+ * @VIPS_FOREIGN_PNG_FILTER_SUB: difference to the left
+ * @VIPS_FOREIGN_PNG_FILTER_UP: difference up
+ * @VIPS_FOREIGN_PNG_FILTER_AVG: average of left and up
+ * @VIPS_FOREIGN_PNG_FILTER_PAETH: pick best neighbor predictor automatically
+ * @VIPS_FOREIGN_PNG_FILTER_ALL: adaptive
  *
  * http://www.w3.org/TR/PNG-Filters.html
  * The values mirror those of png.h in libpng.
@@ -454,8 +454,7 @@ typedef enum /*< flags >*/ {
 	VIPS_FOREIGN_PNG_FILTER_UP = 0x20,
 	VIPS_FOREIGN_PNG_FILTER_AVG = 0x40,
 	VIPS_FOREIGN_PNG_FILTER_PAETH = 0x80,
-	VIPS_FOREIGN_PNG_FILTER_ALL = 0xEA,
-	VIPS_FOREIGN_PNG_FILTER_LAST = 0xFF
+	VIPS_FOREIGN_PNG_FILTER_ALL = 0xEA
 } VipsForeignPngFilter;
 
 int vips_pngload( const char *filename, VipsImage **out, ... )

libvips/include/vips/util.h

@@ -165,6 +165,7 @@ G_STMT_START { \
 const char *vips_enum_string( GType enm, int value );
 const char *vips_enum_nick( GType enm, int value );
 int vips_enum_from_nick( const char *domain, GType type, const char *str );
+int vips_flags_from_nick( const char *domain, GType type, const char *nick );
 
 gboolean vips_slist_equal( GSList *l1, GSList *l2 );
 void *vips_slist_map2( GSList *list, VipsSListMap2Fn fn, void *a, void *b );

libvips/iofuncs/enumtypes.c

@@ -118,10 +118,9 @@ vips_foreign_png_filter_get_type( void )
 			{VIPS_FOREIGN_PNG_FILTER_AVG, "VIPS_FOREIGN_PNG_FILTER_AVG", "avg"},
 			{VIPS_FOREIGN_PNG_FILTER_PAETH, "VIPS_FOREIGN_PNG_FILTER_PAETH", "paeth"},
 			{VIPS_FOREIGN_PNG_FILTER_ALL, "VIPS_FOREIGN_PNG_FILTER_ALL", "all"},
-			{VIPS_FOREIGN_PNG_FILTER_LAST, "VIPS_FOREIGN_PNG_FILTER_LAST", "last"},
 			{0, NULL, NULL}
 		};
-
+		
 		etype = g_flags_register_static( "VipsForeignPngFilter", values );
 	}
 

libvips/iofuncs/object.c

@@ -1961,7 +1961,7 @@ vips_object_set_argument_from_string( VipsObject *object,
 		g_value_set_enum( &gvalue, i );
 	}
 	else if( G_IS_PARAM_SPEC_FLAGS( pspec ) ) {
-		/* Hard to set from a symbolic name. Just take an int.
+		/* Allow a symbolic name, or an int. 
 		 */
 		int i;
 
@@ -1970,7 +1970,9 @@ vips_object_set_argument_from_string( VipsObject *object,
 			return( -1 );
 		}
 
-		if( sscanf( value, "%d", &i ) != 1 ) {
+		if( sscanf( value, "%d", &i ) != 1 &&
+			(i = vips_flags_from_nick( class->nickname, 
+			otype, value )) < 0 ) {
 			vips_error( class->nickname,
 				_( "'%s' is not an integer" ), value );
 			return( -1 );

libvips/iofuncs/util.c

@@ -1597,6 +1597,40 @@ vips_enum_from_nick( const char *domain, GType type, const char *nick )
 	return( -1 );
 }
 
+int
+vips_flags_from_nick( const char *domain, GType type, const char *nick )
+{
+	GTypeClass *class;
+	GFlagsClass *gflags;
+	GFlagsValue *flags_value;
+	int i;
+	char str[1000];
+	VipsBuf buf = VIPS_BUF_STATIC( str );
+
+	if( !(class = g_type_class_ref( type )) ) {
+		vips_error( domain, "%s", _( "no such flag type" ) ); 
+		return( -1 );
+	}
+	gflags = G_FLAGS_CLASS( class );
+
+	if( (flags_value = g_flags_get_value_by_name( gflags, nick )) ) 
+		return( flags_value->value );
+	if( (flags_value = g_flags_get_value_by_nick( gflags, nick )) ) 
+		return( flags_value->value );
+
+	for( i = 0; i < gflags->n_values; i++ ) {
+		if( i > 0 )
+			vips_buf_appends( &buf, ", " );
+		vips_buf_appends( &buf, gflags->values[i].value_nick );
+	}
+
+	vips_error( domain, _( "flags '%s' has no member '%s', " 
+		"should be one of: %s" ),
+		g_type_name( type ), nick, vips_buf_all( &buf ) );
+
+	return( -1 );
+}
+
 /* Scan @buf for the first "%ns" (eg. "%12s") and substitute the 
  * lowest-numbered one for @sub. @buf is @len bytes in size.
  *