Hardcode Exif orientation in thumbnails

fiv-io.h

@@ -108,6 +108,14 @@ typedef enum _FivIoOrientation {
 	FivIoOrientation270       = 8
 } FivIoOrientation;
 
+/// Returns whether dimensions need to be swapped for rendering.
+gboolean fiv_io_orientation_is_sideways(FivIoOrientation orientation);
+
+/// Returns a rendering matrix for a surface. Dimensions need to be pre-swapped.
+cairo_matrix_t fiv_io_orientation_matrix(
+	FivIoOrientation orientation, double width, double height);
+
+/// Extracts the orientation field from Exif, if there's any.
 FivIoOrientation fiv_io_exif_orientation(const guint8 *exif, gsize len);
 
 /// Save metadata attached by this module in Exiv2 format.