photocraft/crates/raw

photocraft-raw

A clean-room, pure-Rust camera raw decoder and developer. The crate is standalone (no workspace dependencies), has no unsafe, does no I/O (&[u8] in), builds for wasm32-unknown-unknown (sequential there, rayon-parallel on native) and never panics on hostile input: every offset is bounds-checked and sizes are checked against Limits before allocating.

use photocraft_raw::{develop, DevelopOptions, Demosaic};

let dev = develop(&bytes, &DevelopOptions { demosaic: Demosaic::Ahd, ..Default::default() })?;
// dev.rgb: interleaved 16-bit RGB in ProPhoto RGB (ROMM primaries, D50, gamma 1.8)
// dev.warnings: anything approximated or not applied

photocraft-io uses it so opening a raw file yields a normal 16-bit RGB document tagged with the built-in ProPhoto-compatible profile.

Sources (clean-room)

Implemented only from public specifications, papers and observation of files:

• TIFF 6.0, TIFF/EP (ISO 12234-2) and the Adobe DNG Specification 1.7.
• ITU-T T.81 (ISO 10918-1) Annex H: lossless JPEG, process 14 ("LJ92").
• The published description of Canon's CR2 container (header, raw IFD, slice tag 0xC640).
• Publicly documented maker-note / private tags (ExifTool's tag tables): Canon SensorInfo (0x00E0) and ColorData (0x4001), Nikon WB_RBLevels (0x000C) and BlackLevel (0x003D), Sony BlackLevel (0x7310), WB_RGGBLevels (0x7313), SonyRawFileType (0x7000) and SonyToneCurve (0x7010), the PanasonicRaw IFD0 tags, Olympus ImageProcessing (0x2040) and CameraSettings (0x2020) preview tags.
• Sony cRAW (ARW 2): H. Dietz, "Sony ARW2 Compression: Artifacts And Credible Repair" (Electronic Imaging 2016) and the RawDigger / diglloyd write-ups of the 11 + 7-bit scheme; the exact bit layout and tone-curve scale were established by observation of sample files.
• Panasonic RW2 RawFormat 5 and uncompressed Olympus ORF: established by observation of sample files (bit packing, page layout, sample justification).
• Demosaicing: Malvar, He & Cutler (ICASSP 2004); Hirakawa & Parks, "Adaptive homogeneity-directed demosaicing" (IEEE TIP 2005).
• McCamy's CCT approximation (1992); the Bradford chromatic adaptation transform.

No code from dcraw, LibRaw, rawspeed, rawler, rawloader or darktable was read or used, and no camera colour tables were copied.

Support matrix

Format	Status
DNG	Uncompressed (8–16 bit, packed or not) and lossless JPEG; strips and tiles; CFA (Bayer) and LinearRaw; LinearizationTable, BlackLevel (+ repeat, DeltaH/V), WhiteLevel, ActiveArea, DefaultCrop, ColorMatrix1/2, CameraCalibration, ForwardMatrix, AnalogBalance, AsShotNeutral / AsShotWhiteXY, BaselineExposure, Orientation, OpcodeList2 GainMap (lens shading)
DNG (lossy JPEG, JPEG XL, floating point; opcodes other than GainMap)	Unsupported / not applied (reported)
CR2	Lossless JPEG with slices, borders and as-shot white balance from the maker note, black measured on the masked border
CR2 sRAW / mRAW	Unsupported
NEF / NRW, ARW, PEF and other TIFF/EP raws	Uncompressed and lossless-JPEG (incl. Sony lossless ARW) CFA data
Sony compressed ARW ("cRAW", SonyRawFileType 2)	Decoded: 11-bit min/max + 7-bit delta blocks, SonyToneCurve to 14 bits
Panasonic / Leica RW2, RawFormat 5 (12- and 14-bit packed)	Decoded, with PanasonicRaw black / white / WB / sensor borders
Olympus ORF, uncompressed 16-bit (E-1, E-400…)	Decoded, with ImageProcessing black / WB / ValidBits / crop
Nikon compressed NEF (lossless and lossy), Sony "Compressed RAW 2", Pentax compressed PEF, RW2 RawFormat 4 and older, Olympus compressed ORF	Unsupported: no public description of these codes was found apart from GPL decoder source, which this crate may not use (clean-room). photocraft-io opens the embedded JPEG preview instead
CR3, RAF	Recognised, unsupported (preview fallback where a preview is found)
X-Trans and other non-Bayer CFAs	Unsupported

Development pipeline

1. Linearization table, per-position black level, scale to the white level.
2. White balance (as shot; or grey-world when the file has none; or explicit multipliers), normalized so the smallest multiplier is 1, then clip to 1 so blown highlights stay white.
3. Demosaic: Bilinear, Mhc (Malvar–He–Cutler) or Ahd (default).
4. Camera → XYZ (D50) per the DNG specification (ColorMatrix interpolated by the white's correlated colour temperature, or ForwardMatrix), → linear ProPhoto; exposure (BaselineExposure + user EV); gamma 1.8; 16 bits.
5. Orientation.

Files without colour calibration (CR2, NEF, ARW, RW2, ORF…) use a documented neutral fallback: the white-balanced camera channels are treated as linear sRGB primaries (colours are plausible but less saturated than a calibrated profile; converting to DNG gives calibrated colour). No tone curve is applied: the result is a scene-referred rendering, flatter than a camera JPEG.

Tools

cargo run --release -p photocraft-raw --example rawinfo -- [--dump] [--demosaic ahd] [--png DIR] FILE... prints what was decoded, times decode and develop, and can write sRGB PNG previews and the embedded JPEG previews.