Nom-Exif

nom-exif is a pure Rust library for both image EXIF and video / audio track metadata through a single unified API. Built on nom.

Highlights

• Pure Rust — no FFmpeg, no libexif, no system deps; cross-compiles cleanly.
• Image and video / audio in one crate — MediaParser dispatches to the right backend by detected MIME, no per-format wrappers.
• Motion Photo support — Pixel and Samsung Motion Photos (JPEG with an embedded MP4) are detected automatically; parse_track extracts the embedded video's track metadata.
• RAW format support — Canon CR3, Fujifilm RAF, Phase One IIQ, alongside JPEG / HEIC / TIFF.
• Three input modes — files, arbitrary Read / Read + Seek (network streams, pipes), or in-RAM bytes (WASM, mobile, HTTP proxies).
• Sync and async unified under one MediaParser.
• Eager (Exif, get-by-tag) or lazy (ExifIter, parse-on-demand) — per-entry errors surface in both modes (Exif::errors() / per-iter Result), so one bad tag doesn't poison the parse.
• Allocation-frugal — parser buffer is recycled across calls; sub-IFDs share the same allocation (no deep copies).
• Fuzz-tested with cargo-fuzz against malformed and adversarial input.

Supported File Types

• Image: JPEG, PNG, HEIC/HEIF, AVIF, TIFF, Phase One IIQ, Fujifilm RAF, Canon CR3
• Video/Audio: MP4, MOV, 3GP (ISOBMFF); MKV, WEBM, MKA (Matroska)

Quick Start

use nom_exif::{read_exif, read_track, read_metadata, ExifTag, TrackInfoTag, Metadata};

// One image:
let exif = read_exif("./testdata/exif.jpg")?;
let make = exif.get(ExifTag::Make).and_then(|v| v.as_str());

// One video:
let info = read_track("./testdata/meta.mov")?;
let model = info.get(TrackInfoTag::Model).and_then(|v| v.as_str());

// Auto-detect:
match read_metadata("./testdata/exif.jpg")? {
    Metadata::Exif(_)  => { /* image */ }
    Metadata::Track(_) => { /* video/audio */ }
}
# Ok::<(), nom_exif::Error>(())

Reusable Parser

For batch processing, build a MediaParser once and reuse its buffer across calls:

use nom_exif::{MediaKind, MediaParser, MediaSource, ExifTag, TrackInfoTag};

let mut parser = MediaParser::new();

let files = [
    "./testdata/exif.heic",
    "./testdata/exif.jpg",
    "./testdata/meta.mov",
];

for f in files {
    let ms = MediaSource::open(f)?;
    match ms.kind() {
        MediaKind::Image => {
            let iter = parser.parse_exif(ms)?;
            let exif: nom_exif::Exif = iter.into();
            let _ = exif.get(ExifTag::Make);
        }
        MediaKind::Track => {
            let info = parser.parse_track(ms)?;
            let _ = info.get(TrackInfoTag::Make);
        }
    }
}
# Ok::<(), nom_exif::Error>(())

MediaSource accepts any Read (or Read + Seek):

• MediaSource::open(path) — convenience for files.
• MediaSource::seekable(reader) — any Read + Seek source.
• MediaSource::unseekable(reader) — Read-only source (e.g. a network stream); slower for formats that store metadata at the end of the file (such as .mov).

Motion Photos

Pixel and Samsung phones store Motion Photos as a single JPEG with a short MP4 video appended after the image data. parse_exif reads the photo's EXIF as usual and sets a flag when it sees the GCamera:MotionPhoto="1" XMP signal; parse_track on the same source then extracts the embedded MP4's metadata.

use nom_exif::{MediaParser, MediaSource, TrackInfoTag};

let path = "PXL_20240101_120000000.MP.jpg";
let mut parser = MediaParser::new();

// 1. Parse the still image as usual.
let iter = parser.parse_exif(MediaSource::open(path)?)?;
println!("has_embedded_track = {}", iter.has_embedded_track());

// 2. If true, re-open the source (parse_exif consumed it) and call
//    parse_track to extract the embedded MP4's metadata.
if iter.has_embedded_track() {
    let track = parser.parse_track(MediaSource::open(path)?)?;
    println!("video {:?}x{:?}",
        track.get(TrackInfoTag::Width),
        track.get(TrackInfoTag::Height));
}
# Ok::<(), nom_exif::Error>(())

has_embedded_track is content-detected, not a MIME-level guess — a plain JPEG without the Motion Photo XMP returns false and parse_track returns Error::TrackNotFound.

Coverage: Pixel/Google Motion Photos and Samsung Galaxy Motion Photos that use the Adobe XMP Container directory format (modern Pixel including Ultra HDR, modern Galaxy JPEGs).

In-Memory Bytes

When the payload is already in RAM (decoded HTTP body, WASM-loaded asset, mobile-cached blob), use MediaSource::from_memory to skip the File / Read round-trip. Memory mode is zero-copy: the underlying allocation is shared with the returned Exif / ExifIter / TrackInfo via bytes::Bytes reference counting.

use nom_exif::{MediaSource, MediaParser, ExifTag};

let raw: Vec<u8> = std::fs::read("./testdata/exif.jpg")?;
let ms = MediaSource::from_memory(raw)?;
let mut parser = MediaParser::new();
let iter = parser.parse_exif(ms)?;
let exif: nom_exif::Exif = iter.into();
let make = exif.get(ExifTag::Make).and_then(|v| v.as_str());
# let _ = make; Ok::<(), nom_exif::Error>(())

MediaSource::from_memory accepts anything convertible into bytes::Bytes: Vec<u8>, &'static [u8], Bytes, and HTTP-body types that implement Into<Bytes> directly.

Format-Specific Metadata (parse_image_metadata)

Some image formats carry metadata that doesn't fit the EXIF/IFD model — PNG tEXt chunks are the headline example. The new (v3.3+) MediaParser::parse_image_metadata returns a structured ImageMetadata { exif, format } covering both:

use nom_exif::{MediaParser, MediaSource, ImageFormatMetadata};

let mut parser = MediaParser::new();
let ms = MediaSource::open("./testdata/exif.png")?;
let img = parser.parse_image_metadata(ms)?;

if let Some(ImageFormatMetadata::Png(text_chunks)) = img.format {
    let _title = text_chunks.get("Title");
    let _software = text_chunks.get("Software");
}
# Ok::<(), nom_exif::Error>(())

img.exif is the standard Option<ExifIter> — convert to Exif with .into() and read tags as in any other example.

For PNG specifically, this also captures legacy EXIF embedded in Raw profile type exif / Raw profile type APP1 tEXt chunks (ImageMagick / Photoshop pattern) — those are transparently hex-decoded and merged into img.exif. The original tEXt entry is still visible via img.format.

parse_image_metadata accepts the same source types as parse_exif: files, in-memory bytes (via MediaSource::from_memory), and async sources. The top-level read_image_metadata convenience helper is deferred to v4 (alongside the planned Metadata enum redesign).

Two API styles for Exif

The library exposes both eager and lazy views of EXIF metadata.

use nom_exif::{read_exif, read_exif_iter, ExifTag};

// Eager — easiest. Get-by-tag, parsed up front.
let exif = read_exif("./testdata/exif.jpg")?;
let make = exif.get(ExifTag::Make).and_then(|v| v.as_str());

// Lazy — finer-grained. Parse-on-demand, per-entry errors visible.
let iter = read_exif_iter("./testdata/exif.jpg")?;
for entry in iter {
    let _tag = entry.tag();          // TagOrCode (Tag(...) or Unknown(code))
    let _ifd = entry.ifd();          // IfdIndex
    let _ = entry.into_result();      // Result<EntryValue, EntryError>
}
# Ok::<(), nom_exif::Error>(())

Async API

Enable the tokio feature in your Cargo.toml:

[dependencies]
nom-exif = { version = "3", features = ["tokio"] }

Then use the _async helpers, or call parse_exif_async / parse_track_async on a MediaParser directly:

# #[cfg(feature = "tokio")]
# async fn demo() -> nom_exif::Result<()> {
use nom_exif::{read_exif_async, MediaParser, AsyncMediaSource};

// One-shot:
let exif = read_exif_async("./testdata/exif.jpg").await?;

// Reusable:
let mut parser = MediaParser::new();
let ms = AsyncMediaSource::open("./testdata/exif.jpg").await?;
let iter = parser.parse_exif_async(ms).await?;
# let _ = (exif, iter); Ok(())
# }

GPS Info

Exif and TrackInfo both expose gps_info(). ExifIter adds parse_gps() for early termination once GPS tags have been read.

use nom_exif::{read_exif, LatRef, LonRef, Altitude};

let exif = read_exif("./testdata/exif.heic")?;
if let Some(g) = exif.gps_info() {
    let _ = matches!(g.latitude_ref, LatRef::North | LatRef::South);
    let _ = matches!(g.longitude_ref, LonRef::East | LonRef::West);
    let _ = matches!(g.altitude, Altitude::AboveSeaLevel(_) | Altitude::BelowSeaLevel(_));
    let _iso = g.to_iso6709();
}
# Ok::<(), nom_exif::Error>(())

Migration from v2

v3.0.0 reshapes the public API end-to-end. The full migration guide lives in docs/MIGRATION.md — every row there is exercised by tests/migration_guide.rs. A few high-traffic items:

• MediaSource::file_path(p) → MediaSource::open(p) or read_exif(p).
• parser.parse::<_,_,ExifIter>(ms) → parser.parse_exif(ms).
• parser.parse::<_,_,TrackInfo>(ms) → parser.parse_track(ms).
• entry.take_result() (panicky) → entry.into_result() (consumes self).
• iter.parse_gps_info() → iter.parse_gps().
• info.get_gps_info() → info.gps_info() (returns Option<&GPSInfo>).
• g.latitude_ref == 'N' → matches!(g.latitude_ref, LatRef::North).
• Cargo features: async → tokio, json_dump → serde.

CLI Tool rexiftool

rexiftool is a companion CLI built on nom-exif, published as a separate crate:

cargo install rexiftool
rexiftool photo.heic        # key => value
rexiftool photo.heic -j     # JSON
rexiftool ./photos/         # batch (non-recursive)

Pre-built binaries (macOS Intel / Apple Silicon, Linux x86_64, Windows x86_64) are attached to each rexiftool-v* GitHub release. Full usage docs: crates/rexiftool/README.md or crates.io/crates/rexiftool.

Contributing

Enable the repository's pre-commit hook once per clone so commits that would fail cargo fmt --check in CI are rejected locally:

git config core.hooksPath .githooks

The hook lives in .githooks/pre-commit and runs cargo fmt --check (sub-second). Bypass with git commit --no-verify for emergencies.

Fuzz Testing

The project uses cargo-fuzz (libFuzzer) for fuzz testing. Requires nightly Rust.

Run the fuzzer:

# Use testdata/ as seed corpus, write new corpus to fuzz/corpus/media_parser/
cargo +nightly fuzz run media_parser fuzz/corpus/media_parser/ testdata/

Reproduce a crash:

cargo +nightly fuzz run media_parser fuzz/artifacts/media_parser/<crash-file>

Minimize a crash input:

cargo +nightly fuzz tmin media_parser fuzz/artifacts/media_parser/<crash-file>

Changelog

CHANGELOG.md