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CTB

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AutoCAD Plot Style Table.

At a glance
Original creator Autodesk (AutoCAD)
Purpose An AutoCAD colour-dependent plot style table: how each of the 255 colour indices prints, with pen colour, screening, lineweight, linetype and line end and join styles.
Extensions .ctb
Poka parser poka-ctb
Viewer poka-tree-viewer
Depth tier Parser with a shared viewer (see Depth tiers)
Breadth tier B2 Broad (see Breadth tiers)

How much Poka reads

B2 Broad. The common content of the current and the common older versions is decoded. Some named features or versions are not, and are listed.

Confidence: high (the reviewer read the code and a test that proves the claim). Basis: Reviewed 2026-10-16: parsers/poka-ctb/src/lib.rs (header, length check, zlib inflate, brace parser, tree builder, unit tests) and tests/samples.rs run over the 4 real corpus tables (ixhlbxi_arm, lendres_standard_full_size, opencadstudio_ocad, pirogoeth_navfacstnd). Covers CTBVER1 colour-dependent tables with the pmzlibcodec zlib wrapper, the only variant Poka claims.

What Poka does not read

  • linetype codes 0 to 30 are named from ezdxf's documentation of the plot style editor's linetype list; no corpus table sets one (all four use 31), so the code-to-name pairing is not checked against a real file
  • the aci_table block (per-colour-index names) is not shown
  • pen number and virtual pen assignments are shown as raw numbers, not explained
  • named plot style tables (.stb) and any CTB without the pmzlibcodec wrapper are rejected, not read
  • no indication of which colour indices are actually used by a drawing

Background

The file starts with an ASCII header line (PIAFILEVERSION_2.0,CTBVER1,compress) and a codec tag, then three little-endian lengths and a zlib stream; it is not plain text. The inflated payload is a brace-structured configuration. Poka checks the declared lengths against the stream before trusting it, inflates it and shows the table per colour index, so a reader can see whether a drawing plots in colour or greyscale and at what line weights without opening AutoCAD.

Versions

Version Identifier Poka Note
CTBVER1 PIAFILEVERSION_2.0,CTBVER1,compress Read

Libraries

Libraries Poka uses or has assessed for this format, with the status, licence and language the registry records.

Sources