cairo-surface-write-to-png (surface filename)

surface -- a cairo-surface-t instance with pixel contents
filename -- a string with the name of a file to write to

:success if the PNG file was written successfully. Otherwise, :no-memory if memory could not be allocated for the operation or :surface-type-mismatch if the surface does not have pixel contents, or :write-error if an I/O error occurs while attempting to write the file.

Writes the contents of the image surface to a new file as a PNG image.