PNG Support Reading and writing PNG images The PNG functions allow reading PNG images into image surfaces, and writing any surface to a PNG file. #cairo_surface_t Defined if the PNG functions are available. This macro can be used to conditionally compile code using the cairo PNG functions. @filename: @Returns: @closure: @data: @length: @Returns: @read_func: @closure: @Returns: @surface: @filename: @Returns: @closure: @data: @length: @Returns: @surface: @write_func: @closure: @Returns: