Macro putString 

macro_rules! putString {
    ($val:ident,$key:ident,$typ:ident,$slf:ident.$($x:ident).+) => { ... };
}

Put a variable length UTF8 string into the image using the given key path.

putString!(val:&str,key_path:&Vec<String>,image_type:String,self.path.to.string:String)