RCF tools

Tools to read Rapiscan proprietary .RCF X-ray scans (Rapiscan 618XR) and compare devices.

File	Purpose
rcf-viewer.html	Self-contained browser viewer: folder explorer, dual-energy views, region measurements. Works offline.
rcf_decode.py	Batch decoder: exports both energy channels to .npz plus a preview PNG.

Viewer

Open rcf-viewer.html in a recent browser (Chrome, Edge, Firefox, Safari). No server and no network access are needed; files are decoded locally and never leave the machine.

• Open folder loads a folder tree; only .RCF files are listed.
• Files are grouped by folder or by acquisition date, parsed from the file name <device>_<YYYYMMDDhhmmssSSS>_<tag>.RCF (e.g. 6201219_20261028162201833_SCREENER.RCF = 2026-10-28 16:22:01.833).
• ↑ / ↓ step through scans; the next scans are decoded in advance.
• Views: channel A, channel B, attenuation −ln(I/I₀) of each, and the attenuation ratio A/B.
• Select region measures mean and standard deviation in a rectangle; the region and the contrast window are kept across scans. Measurements can be copied as TSV.

Folder selection is not available on iOS and not always on Android; use Open files there.

Decoder

pip install numpy pillow
python rcf_decode.py path/to/*.RCF --out decoded

Prints a smoothness score per file; a high score means the encoding differs from the validated one.

RCF format (reverse-engineered)

Validated on a single file from one machine. Re-check on new machines or software versions.

• Sequence of chunks, each starting with 11 11 FF FF, followed by a 28-byte header of 7 little-endian uint32: [marker, type, ?, ?, ?, first_record_index, records_in_chunk].
• Type 3 chunks hold the image. Payloads concatenated in file order form the scan.
• 944 detector pixels per line; one pixel = one uint32 = two uint16 channels:
  • channel A = bits 0–15 (lower noise, higher contrast, likely low energy),
  • channel B = bits 16–31 (likely high energy).
• The high byte of each channel is bit-rotated: rotate left by 5 (A) and by 7 (B) to decode. The low byte looks like noise and its encoding is unconfirmed, so only 8 bits per channel are used.
• Values are transmitted intensity (air ≈ 227). Linearity is unknown; calibrate with a step wedge before quantitative work.
• Other chunk types (metadata, likely obfuscated strings) are not decoded.

Data handling

Scans are excluded by .gitignore. Do not commit .RCF files, exports, or measurement tables that identify devices.