Crate djvu_jb2 

JB2 bilevel image decoder — clean-room implementation (phase 2b).

Decodes JB2-encoded bitonal images from DjVu Sjbz and Djbz chunks. The JB2 format uses a ZP adaptive arithmetic coder with 262 context variables and a symbol dictionary for run-length compression of recurring glyphs.

Key public types

• Jb2Dict — shared symbol dictionary decoded from a Djbz chunk
• decode — decode a Sjbz image stream to a Bitmap
• decode_dict — decode a Djbz dictionary stream to a Jb2Dict

Record types

Code	Meaning
0	start-of-image
1	new-symbol, add to dict AND blit to page
2	new-symbol, add to dict only
3	new-symbol (direct), blit only (not added to dict)
4	matched-refine, add to dict AND blit
5	matched-refine, add to dict only
6	matched-refine, blit only
7	matched-copy (no refinement), blit only
8	non-symbol (halftone block), blit only
9	required-dict-or-reset
10	comment
11	end-of-data

Structs

Jb2Dict

A shared JB2 symbol dictionary decoded from a Djbz chunk.

Enums

Jb2Error

JB2 bitonal image decoding errors.

Functions

decode

Decode a JB2 image stream (Sjbz chunk data) into a Bitmap.

decode_dict

Decode a JB2 dictionary stream (Djbz chunk data) into a Jb2Dict.

decode_indexed

Decode a JB2 image stream with per-pixel blit index tracking.