poka.sh

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BMP

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Windows BMP Preview.

At a glance
Original creator Microsoft
Purpose Device-independent bitmap images, originally and mainly on Windows and OS/2.
Extensions .bmp
Poka parser poka-bmp
Viewer poka-image-with-meta-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: medium (the reviewer read the code). Basis: Reviewed 2026-10-16: parsers/poka-bmp/src/lib.rs (decode via image BmpDecoder under decode_within_budget, header_facts over DIB header, bpp, compression, row order, resolution), unit tests, tests/samples.rs (OS/2 core header, BITMAPINFOHEADER, RLE4, RLE8, BITFIELDS, 72 dpi); corpus header scan: 40-byte headers at 1/4/8/16/24/32 bpp, 12-byte OS/2, 108-byte V4, RLE4/RLE8, BITFIELDS, no V5. Decoder limits read in image-0.25.10 bmp/decoder.rs. Wasm route only: desktop hands the file to the webview.

What Poka does not read

  • BI_JPEG and BI_PNG compressed BMPs are rejected by the decoder
  • CMYK BMPs are rejected
  • colour space and gamma fields (V4/V5) and embedded or linked ICC profiles are ignored
  • no V5 (124-byte header) sample in the corpus
  • OS/2 BITMAPCOREHEADER2 is named but decoding is not verified
  • files whose declared size exceeds the 48 MiB decode budget are refused with metadata only

Background

The Library of Congress says several backwards-compatible versions came with new versions of Windows, the current one being version 5. Poka decodes the file with the image crate and shows it as a PNG, with the header type and other facts; the declared size is checked against the memory budget before any pixel is decoded.

Versions

Version Identifier Poka Note
OS/2 core headers, BITMAPINFOHEADER, BITMAPV4HEADER and BITMAPV5HEADER BM Not recorded The module names each header type it meets; decoding is the image crate's. Decoding of OS/2 BITMAPCOREHEADER2 is named but not verified, and the corpus holds no version 5 file.

Libraries

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

Sources