added vips_image_write()

added a convenience function to write an image to a file

libvips/include/vips/image.h

@@ -363,6 +363,7 @@ VipsImage *vips_image_new_from_file_raw( const char *filename,
 VipsImage *vips_image_new_from_memory( void *buffer, 
 	int xsize, int ysize, int bands, VipsBandFormat bandfmt );
 VipsImage *vips_image_new_disc_temp( const char *format );
+int vips_image_write( VipsImage *image, const char *filename );
 
 gboolean vips_image_isMSBfirst( VipsImage *image );
 gboolean vips_image_isfile( VipsImage *image );

libvips/iofuncs/image.c

@@ -1736,6 +1736,31 @@ vips_image_new_disc_temp( const char *format )
 	return( image );
 }
 
+/**
+ * vips_image_write:
+ * @image: image to write
+ * @filename: write to this file
+ *
+ * A convenience function to write a #VipsImage to a file. 
+ *
+ * Returns: 0 on success, or -1 on error.
+ */
+int
+vips_image_write( VipsImage *image, const char *filename )
+{
+	VipsImage *out;
+
+	if( !(out = vips_image_new_from_file( filename, "w" )) )
+		return( -1 );
+	if( im_copy( image, out ) ) {
+		g_object_unref( out );
+		return( -1 );
+	}
+	g_object_unref( out );
+
+	return( 0 );
+}
+
 /**
  * vips_image_isMSBfirst:
  * @image: image to test

libvips/iofuncs/object.c

@@ -1164,18 +1164,13 @@ vips_object_get_argument_to_string( VipsObject *object,
 	if( G_IS_PARAM_SPEC_OBJECT( pspec ) && 
 		G_PARAM_SPEC_VALUE_TYPE( pspec ) == VIPS_TYPE_IMAGE ) {
 		VipsImage *value;
-		VipsImage *image;
 
-		if( !(image = vips_image_new_from_file( arg, "w" )) )
-			return( -1 );
 		g_object_get( object, name, &value, NULL );
-		if( im_copy( value, image ) ) {
+		if( vips_image_write( value, arg ) ) {
 			g_object_unref( value );
-			g_object_unref( image );
 			return( -1 );
 		}
 		g_object_unref( value );
-		g_object_unref( image );
 	}
 	else {
 		char str[1000];