Changelog

0.1.0 - 2026-07-16

This is a breaking release. It replaces the panic-based file API with a typed Result, changes two public field types, and preserves more of the precision and semantics stored in EXIF rational and ASCII values.

Breaking Changes

• glexif.get_exif_data_for_file/1 now returns Result(exif_tag.ExifTagRecord, glexif.ExifError) instead of returning an ExifTagRecord directly. There is no legacy panic-based wrapper.
• ExifTagRecord.x_resolution and ExifTagRecord.y_resolution now use Option(Float) instead of Option(Int). The same change applies to ExifTagRecordSimple.
• ExifTagRecord.sub_sec_time_original and ExifTagRecord.sub_sec_time_digitized now use Option(String) instead of Option(Int). The same change applies to ExifTagRecordSimple. EXIF stores these fields as ASCII, so values such as "079" now retain leading zeroes.
• Rational-derived float fields preserve source precision instead of applying display rounding. Exact output may change for F-number, aperture value, brightness value, focal length, and fractional X/Y resolution. Consumers comparing floats should use an appropriate tolerance.
• ApertureValue is now exposed as an F-number calculated from its APEX value with 2^(APEX / 2). Code relying on the previous direct rational value must update its interpretation.
• BrightnessValue and ExposureCompensation now decode signed TIFF rationals correctly. Negative values that were previously interpreted as large unsigned values now produce negative floats.

Typed Error API

• Added the public glexif.ExifError type for file open, read, and close failures; missing EXIF; truncated input; invalid JPEG, EXIF, and TIFF structure; invalid entries and offsets; offset cycles; and traversal limits.
• Added glexif.ExifMarkerNotFound as the stable result when a readable JPEG reaches image data or end-of-image without an EXIF candidate. An APP1 payload beginning with Exif is treated as a candidate; if its required Exif\0\0 header is malformed, parsing returns InvalidExifHeader.
• Added glexif.error_to_string/1 for stable diagnostic formatting.
• Opened file streams are closed on both successful and failed parsing paths. If parsing and closing both fail, the parsing error is retained.

Parsing And Correctness

• JPEG parsing now validates the start-of-image marker and walks declared JPEG segment boundaries rather than scanning arbitrary byte pairs.
• APP1 payloads that do not begin with Exif, including XMP, are ignored while searching. The first Exif-prefixed candidate is validated and either parsed or returned as an error. Searching stops at start-of-scan or end-of-image.
• EXIF and TIFF headers now validate their complete structure, including TIFF byte order, magic value, and declared first-IFD offset.
• IFD traversal now validates table bounds and linked EXIF, GPS, and next-IFD pointers. Offset cycles and excessive traversal return typed errors.
• TIFF values continue to follow the standard inline-versus-offset rule: values up to four bytes are inline, while larger values use offsets relative to the TIFF header.
• Intel and Motorola values are decoded by integer width and byte order. This corrects endian handling for tag IDs, types, counts, offsets, signed and unsigned rationals, multi-component values, and GPS data.
• GPS timestamps now apply each rational denominator. For example, seconds stored as 113/2 are returned as "56.5".
• Exposure program code 9 now maps to Bulb.
• Color space code 0xfffd now maps to WideGamutRGB, and 0xfffe maps to ICCProfile.

Malformed Optional Tags

• Structural JPEG, TIFF, and IFD corruption fails the file with ExifError.
• Unsupported or malformed optional tag values are skipped when they can be isolated safely, allowing other valid metadata to be returned.
• Unknown TIFF data types, invalid optional value offsets, invalid UTF-8, incorrect tag types or component counts, and zero rational denominators no longer panic or fabricate fallback values.
• Skipped optional tags remain None. This release does not expose warnings for skipped tags.

Migration

Before 0.1.0:

let metadata = glexif.get_exif_data_for_file(path)
use_make(metadata.make)

With 0.1.0:

case glexif.get_exif_data_for_file(path) {
  Ok(metadata) -> use_make(metadata.make)
  Error(glexif.ExifMarkerNotFound) -> handle_photo_without_exif()
  Error(error) -> report(glexif.error_to_string(error))
}

Applications that consider a JPEG without EXIF to be valid should translate ExifMarkerNotFound into their own empty or absent metadata representation.

Supported Scope

• Standard EXIF APP1 data in JPEG files.
• Motorola (MM, big-endian) and Intel (II, little-endian) TIFF data.
• Standard, linked EXIF, GPS, and next-IFD traversal.

Maker notes, shutter-speed value, lens info, XMP, PNG EXIF containers, and nonstandard APP1 payloads remain unsupported.

Package Metadata

• Added the GitHub repository URL to the published package metadata.
• Added this changelog to the generated HexDocs pages.
• Moved gleam_json to development dependencies because it is used only by the ExifTool test oracle. Consumers now require only gleam_stdlib and file_streams.
• Updated CI to Gleam 1.17.0.