GimpTile
typedef struct {
guint ewidth; /* the effective width of the tile */
guint eheight; /* the effective height of the tile */
guint bpp; /* the bytes per pixel (1, 2, 3 or 4 ) */
guint tile_num; /* the number of this tile within the drawable */
guint16 ref_count; /* reference count for the tile */
guint dirty : 1; /* is the tile dirty? has it been modified? */
guint shadow: 1; /* is this a shadow tile */
guchar *data; /* the pixel data for the tile */
GimpDrawable *drawable; /* the drawable this tile came from */
} GimpTile;
