drewnoakes/metadata-extractor

Identify thumbnail offset and length tags by name

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#263 opened on Mar 31, 2017

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 (0 comments) (0 reactions) (0 assignees)Java (2,411 stars) (470 forks)batch import
bugformat-exifhelp wanted

Description

After recent changes, these two tags are displayed as unknown.

(From #262):

[Exif SubIFD] - New Subfile Type = Reduced-resolution image
[Exif SubIFD] - Compression = JPEG (old-style)
[Exif SubIFD] - X Resolution = 300 dots per inch
[Exif SubIFD] - Y Resolution = 300 dots per inch
[Exif SubIFD] - Resolution Unit = Inch
[Exif SubIFD] - Unknown tag (0x0201) = 1080832
[Exif SubIFD] - Unknown tag (0x0202) = 1737279
[Exif SubIFD] - YCbCr Positioning = Datum point

0x0201 is thumbnail offset, and 0x0202 is thumbnail length.

Contributor guide

Tech stack
java
Domain
toolingdata
Issue type
bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
2
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
1-3 hours
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
fresh
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
clear
Prerequisites
JavaExif metadata
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
80
Research direction
The issue references specific unknown tags 0x0201 (thumbnail offset) and 0x0202 (thumbnail length) in Exif SubIFD. Review the Exif tag definitions in the metadata extractor codebase, likely in a file like ExifDirectoryBase.java or similar. Add mapping for these two tags with appropriate names. Search for existing tag constants to follow the pattern. No additional comments or PRs are linked, so the implementation is straightforward once the correct location is found.