View Source Pdf.Reader.Filter behaviour (ExPDF v1.0.1)

PDF stream filter pipeline — behaviour definition and apply_chain dispatcher.

Each filter is a module implementing the Pdf.Reader.Filter behaviour with a single decode/2 callback. The apply_chain/3 function runs filters in sequence (outermost first, matching the order in which they appear in the PDF stream's /Filter array).

Supported filters

Module	Filter names
`Pdf.Reader.Filter.Flate`	`FlateDecode`, `Fl`
`Pdf.Reader.Filter.ASCII85`	`ASCII85Decode`, `A85`
`Pdf.Reader.Filter.ASCIIHex`	`ASCIIHexDecode`, `AHx`
`Pdf.Reader.Filter.RLE`	`RunLengthDecode`, `RL`
`Pdf.Reader.Filter.LZW`	`LZWDecode`, `LZW`

Unknown filters return {:error, {:unsupported_filter, name_atom}}.

Summary

Callbacks

decode(binary, params)

Functions

apply_chain(bytes, names, params)

Apply a chain of filters to bytes.

Callbacks

decode(binary, params)

@callback decode(binary(), params :: map()) :: {:ok, binary()} | {:error, term()}

Functions

apply_chain(bytes, names, params)

@spec apply_chain(
  binary(),
  names :: list() | binary() | atom(),
  params :: list() | map()
) ::
  {:ok, binary()} | {:error, term()}

Apply a chain of filters to bytes.

names may be:

A list of filter name strings or atoms (multi-filter case)
A single filter name string or atom (single-filter convenience)

params may be:

A list of param maps (aligned with names)
A single map (used for all filters)
:null entries in the list become %{}

Filters are applied left to right (outermost first per PDF spec). Returns {:ok, decoded_bytes} or {:error, reason}.