urkx / md2pdf

Md2Pdf

Export Markdown files to PDF. Implementing official PDF specification

Ref: https://opensource.adobe.com/dc-acrobat-sdk-docs/pdfstandards/PDF32000_2008.pdf

Running tests

python3 -m pytest test

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Notes

PDF Syntax

• PDF Components

  • Objects.
  • File structure.
  • Document structure.
  • Content streams.

• Non-encrypted PDF can be written in ANSI X3.4-1986.

• Special ASCII-encoded tokens

  • Tokens thar delimit objects, reserved words, certain types of arrays.
  • Data values of strings and streams objects (can be entirely binary data too). Data such as images is represented in binary for compactness.

Objects

• Boolean, Integer, Real, String, Name(PDF 1.2), Array, Dictionary(<<>>), Stream(unlimited length), null.

• Stream objects

  • Consist of a dictionary followed by a stream object

  dictionary
  stream
  ...bytes...
  endstream
  

  • All streams shall be indirect objects and the stream dictionary shall be a direct object.
  • Stream dictionary entries:

  Key	Value
  Length	(Required) Number of bytes of the stream
  Filter	(Optional) Name of the filter to apply to stream data
  DecodeParams	(Optional) Dictionary or array of dictionaries used by the filter specified in Filter
  F	(Optional) File containing the stream data
  FFilter	(Optional) Filter to apply to stream data contained in file F
  FDecodeParams	(Optional) Params of FFilter
  DL	(Optional) Number of bytes in the decoded (defiltered) stream

• May be labeled (called an indirect object)

• Indirect objects

  • Identification: Object number, generation number, obj ... endobj

  10 0 obj
      (String)
  endobj
  

  • Reference to an object: Object number, generation number, R keyword

  10 0 R
  

• Stream filters. Must be specified in the stream dictionary if required

/Filter [/ASCII85Decode /LZWDecode]

Filters

• ASCIIHexDecode, ASCII85Decode
• LZWDecode, FlateDecode

File structure

• Header. One line identifying PDF specification of the file.

• Body. Objects of the document.

• Xref table. Info about indirect objects in the file.

• Trailer. Location of the Xref table and of certain special objects within the body.