This property determines whether the Save method appends to
(rather than overwrites) existing image files.
If this property is set to true and a file already exists then
the Save method appends the rendered image to the exisiing file
rather than just overwriting it. In this way you can build up
For in-memory operations you can use this property set to true
in conjunction with a MemoryStream and the Save overload that
This property is used for TIFF output only.