add @background arg to save

used to flatten A out of images, if necessary

vipsthumbnail rtd-img.png -o x.jpg[background=255]

ChangeLog

@@ -4,6 +4,7 @@
 - add vips_resize()
 - return of vips_init(), but just for bindings
 - revised type.c to make it more binding-friendly
+- add @background arg to save: the colour to flatten against
 
 8/9/14 started 7.40.9
 - support jfif resunit "none"

libvips/conversion/embed.c

@@ -82,7 +82,7 @@ typedef struct _VipsEmbed {
 	VipsImage *in;
 
 	VipsExtend extend;
-	VipsArea *background;
+	VipsArrayDouble *background;
 	int x;
 	int y;
 	int width;
@@ -362,7 +362,8 @@ vips_embed_build( VipsObject *object )
 
 	if( !(embed->ink = vips__vector_to_ink( 
 		class->nickname, embed->in,
-		embed->background->data, NULL, embed->background->n )) )
+		VIPS_AREA( embed->background )->data, NULL, 
+		VIPS_AREA( embed->background )->n )) )
 		return( -1 );
 
 	if( !vips_object_argument_isset( object, "extend" ) &&
@@ -614,9 +615,7 @@ static void
 vips_embed_init( VipsEmbed *embed )
 {
 	embed->extend = VIPS_EXTEND_BLACK;
-	embed->background = 
-		vips_area_new_array( G_TYPE_DOUBLE, sizeof( double ), 1 ); 
-	((double *) (embed->background->data))[0] = 0;
+	embed->background = vips_array_double_newv( 1, 0.0 );
 }
 
 /**

libvips/conversion/flatten.c

@@ -61,7 +61,7 @@ typedef struct _VipsFlatten {
 
 	/* Background colour.
 	 */
-	VipsArea *background;
+	VipsArrayDouble *background;
 
 	/* The [double] converted to the input image format.
 	 */
@@ -319,8 +319,9 @@ vips_flatten_build( VipsObject *object )
 	/* Is the background black? We have a special path for this.
 	 */
 	black = TRUE;
-	for( i = 0; i < flatten->background->n; i++ )
-		if( ((double *) flatten->background->data)[i] != 0.0 ) {
+	for( i = 0; i < VIPS_AREA( flatten->background )->n; i++ )
+		if( vips_array_double_get( flatten->background, NULL )[i] != 
+			0.0 ) {
 			black = FALSE;
 			break;
 		}
@@ -336,8 +337,8 @@ vips_flatten_build( VipsObject *object )
 		 */
 		if( !(flatten->ink = vips__vector_to_ink( class->nickname, 
 			conversion->out, 
-			flatten->background->data, NULL, 
-				flatten->background->n )) )
+			VIPS_AREA( flatten->background )->data, NULL, 
+			VIPS_AREA( flatten->background )->n )) )
 			return( -1 );
 
 		if( vips_image_generate( conversion->out,
@@ -384,9 +385,7 @@ vips_flatten_class_init( VipsFlattenClass *class )
 static void
 vips_flatten_init( VipsFlatten *flatten )
 {
-	flatten->background = 
-		vips_area_new_array( G_TYPE_DOUBLE, sizeof( double ), 1 ); 
-	((double *) (flatten->background->data))[0] = 0.0;
+	flatten->background = vips_array_double_newv( 1, 0.0 );
 }
 
 /**
@@ -397,7 +396,7 @@ vips_flatten_init( VipsFlatten *flatten )
  *
  * Optional arguments:
  *
- * @background: colour for new pixels
+ * @background: #VipsArrayDouble colour for new pixels 
  *
  * Take the last band of @in as an alpha and use it to blend the
  * remaining channels with @background. 

libvips/foreign/foreign.c

@@ -1146,7 +1146,9 @@ vips_foreign_convert_saveable( VipsForeignSave *save )
 			 class->saveable == VIPS_SAVEABLE_RGB_CMYK) ) {
 			VipsImage *out;
 
-			if( vips_flatten( in, &out, 0, NULL ) ) {
+			if( vips_flatten( in, &out, 
+				"background", save->background,
+				NULL ) ) {
 				g_object_unref( in );
 				return( -1 );
 			}
@@ -1414,11 +1416,19 @@ vips_foreign_save_class_init( VipsForeignSaveClass *class )
 		VIPS_ARGUMENT_OPTIONAL_INPUT,
 		G_STRUCT_OFFSET( VipsForeignSave, strip ),
 		FALSE );
+
+	VIPS_ARG_BOXED( class, "background", 101, 
+		_( "Background" ), 
+		_( "Background value" ),
+		VIPS_ARGUMENT_OPTIONAL_INPUT,
+		G_STRUCT_OFFSET( VipsForeignSave, background ),
+		VIPS_TYPE_ARRAY_DOUBLE );
 }
 
 static void
-vips_foreign_save_init( VipsForeignSave *object )
+vips_foreign_save_init( VipsForeignSave *save )
 {
+	save->background = vips_array_double_newv( 1, 0.0 );
 }
 
 /* Can we write this filename with this file? 

libvips/include/vips/foreign.h

@@ -256,10 +256,15 @@ typedef enum {
 typedef struct _VipsForeignSave {
 	VipsForeign parent_object;
 
-	/* Dont't attach metadata.
+	/* Don't attach metadata.
 	 */
 	gboolean strip;
 
+	/* If flattening out alpha, the background colour to use. Default to
+	 * 0 (black).
+	 */
+	VipsArrayDouble *background;
+
 	/*< public >*/
 
 	/* The image we are to save, as supplied by our caller.