ec1f89217a
Full Mattermost server source with integrated Community Enterprise features. Includes vendor directory for offline/air-gapped builds. Structure: - enterprise-impl/: Enterprise feature implementations - enterprise-community/: Init files that register implementations - enterprise/: Bridge imports (community_imports.go) - vendor/: All dependencies for offline builds Build (online): go build ./cmd/mattermost Build (offline/air-gapped): go build -mod=vendor ./cmd/mattermost 🤖 Generated with [Claude Code](https://claude.com/claude-code) Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
75 lines
4.4 KiB
Markdown
75 lines
4.4 KiB
Markdown
[](https://github.com/bep/imagemeta/actions?query=workflow:Test)
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[](https://goreportcard.com/report/github.com/bep/imagemeta)
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[](https://codecov.io/gh/bep/imagemeta)
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[](https://godoc.org/github.com/bep/imagemeta)
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## This is about READING image metadata
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Writing is not supported, and never will.
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I welcome PRs with fixes, but please raise an issue first if you want to add new features.
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## Performance
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Extracting `EXIF` performs well, ref. the benhcmark below. Note that you can get a significant boost if you only need a subset of the fields (e.g. only the `Orientation`). The last line is with the library that [Hugo](https://github.com/gohugoio/hugo) used before it was replaced with this.
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```bash
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BenchmarkDecodeCompareWithGoexif/bep/imagemeta/exif/jpeg/alltags-10 62474 19054 ns/op 4218 B/op 188 allocs/op
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BenchmarkDecodeCompareWithGoexif/bep/imagemeta/exif/jpeg/orientation-10 309145 3723 ns/op 352 B/op 8 allocs/op
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BenchmarkDecodeCompareWithGoexif/rwcarlsen/goexif/exif/jpg/alltags-10 21987 50195 ns/op 175548 B/op 812 allocs/op
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```
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Looking at some more extensive tests, testing different image formats and tag sources, we see that the current XMP implementation leaves a lot to be desired (you can provide your own XMP handler if you want).
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```bash
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BenchmarkDecode/png/exif-10 39164 30783 ns/op 4231 B/op 189 allocs/op
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BenchmarkDecode/png/all-10 5617 206111 ns/op 48611 B/op 310 allocs/op
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BenchmarkDecode/webp/all-10 3069 379637 ns/op 144181 B/op 2450 allocs/op
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BenchmarkDecode/webp/xmp-10 3291 359133 ns/op 139991 B/op 2265 allocs/op
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BenchmarkDecode/webp/exif-10 47028 25788 ns/op 4255 B/op 191 allocs/op
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BenchmarkDecode/jpg/exif-10 58701 20216 ns/op 4223 B/op 188 allocs/op
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BenchmarkDecode/jpg/iptc-10 135777 8725 ns/op 1562 B/op 80 allocs/op
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BenchmarkDecode/jpg/iptc/category-10 215674 5393 ns/op 456 B/op 15 allocs/op
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BenchmarkDecode/jpg/iptc/city-10 192067 6201 ns/op 553 B/op 17 allocs/op
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BenchmarkDecode/jpg/xmp-10 3244 359436 ns/op 139861 B/op 2263 allocs/op
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BenchmarkDecode/jpg/all-10 2874 389489 ns/op 145700 B/op 2523 allocs/op
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BenchmarkDecode/tiff/exif-10 2065 566786 ns/op 214089 B/op 282 allocs/op
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BenchmarkDecode/tiff/iptc-10 16761 71003 ns/op 2603 B/op 133 allocs/op
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BenchmarkDecode/tiff/all-10 1267 933321 ns/op 356878 B/op 2668 allocs/op
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```
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## When in doubt, Exiftool is right
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The output of this library is tested against `exiftool -n -json`. This means, for example, that:
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* We use f-numbers and not APEX for aperture values.
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* We use seconds and not APEX for shutter speed values.
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* EXIF field definitions are fetched from this table: https://exiftool.org/TagNames/EXIF.html
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* IPTC field definitions are fetched from this table: https://exiftool.org/TagNames/IPTC.html
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* The XMP handling is currently very simple, you can supply your own XMP handler (see the `HandleXMP` option) if you need more.
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There are some subtle differences in output:
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* Exiftool prints rationale number arrays as space formatted strings with a format/precision that seems unnecessary hard to replicate, so we use `strconv.FormatFloat(f, 'f', -1, 64)` for these.
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## Development
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Many of the tests depends on generated golden files. To update these, run:
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```bash
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go generate ./gen
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```
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Note that you need a working `exiftool` and updated binary in your `PATH` for this to work. This was tested OK with:
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```
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exiftool -ver
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12.76
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```
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Debuggin tips:
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```bash
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exiftool testdata/goexif_samples/has-lens-info.jpg -htmldump > dump.html
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```
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