Represents the "Filter" entry of the stream object.
It is an optional entry defined as part of the PDF 1.0
It contains an array which contains strings, representing PDF
Items in this array may take one of the following valid
If you read the specification you will see that an array of one
string may be represented as a single string rather than an array.
However we always present this property as an array to simplify the
interface. It is only if you add or remove items in the array, that
the underlying representation will be changed.
The array controls decompression settings.
Each item in the array represents a filter, a compression type,
applied to the data in the stream.
Mutiple filters can be applied to chain compression types. For
example you might wish to apply first Flate compression and then
As new filters are applied to the data, the names are added at
the start of the array. So the array represents the order required
For example if you applied Flate and then ASCII85 encoding, the
first item would be ASCII85Decode and the second FlateDecode.
For definitive details see:.
The ISO PDF Specification, ISO 32000-1:2008 PDF 1.7; Table: 5, page
The ISO PDF
Specification, ISO 32000-2:2017 PDF 2.0; Table: 5, page 32.