Flattens the transparent objects on pages in
The FlattenTransparency operation removes any transparent
objects and replaces them with opaque ones that appear the
Because the look of your PDF does not change it can then be
displayed or printed on a device that does not support
The name 'Flatten' is used because PDF transparency is
represented as a stack of objects. The FlattenTransparency
operation reduces that stack height to one.
The term 'Transparency' covers perhaps more than you might
think. The philosophy on this is that any construct listed in the
'Transparency' section of the PDF reference should be replaced.
Prior to PDF 1.4, objects were always opaque - the color of the
object would become the color of the entire object - whether it was
painted on the background or over previously painted objects.
With PDF 1.4 came the idea that some objects could contain
transparent attributes that would allow a previously painted object
on the page to show through the newly painted object.
These attributes include alpha, which is a numeric value for the
opaqueness of an object.
They also include blend modes, where the color of the underlying
object interacts with the color of the overlying object in some
more complicated manner.
For more information on PDF transparency, please refer to the
Note that this feature is only available under the ABCpdf