Implement the lossless preservation export option #33

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opened 2026-07-28 04:57:31 +00:00 by claude-bot · 0 comments

claude-bot commented

2026-07-28 04:57:31 +00:00

Context

Spec section 12.5 asks for lossless preservation wherever practical. Family scans are
often the only surviving copy of a photograph, and re-encoding them repeatedly degrades
them permanently.

Scope

Lossless export option with optional archival masters alongside derivatives.

Implementation notes

Where the export needs no pixel modification, copy bytes directly rather than decoding
and re-encoding. Metadata-only changes should use a metadata-preserving write path.
If originals are already lossless, record that fact in the manifest.
Optionally emit archival masters alongside derivative JPEGs, for downstream
compatibility without sacrificing the archival copy.
Make the trade-off explicit in the UI: output size against fidelity. Users exporting a
large collection need to know what they are choosing.
Verify that a lossless path genuinely produced identical image data â€” compare decoded
pixel data, not just file size, in tests.
Document which formats support which paths.

Done when

Lossless export produces bit-identical image data where no pixel change is required
Already-lossless originals are recorded as such in the manifest
Archival masters can optionally accompany derivatives
The size/fidelity trade-off is visible in the UI
Losslessness is verified by test, not assumed

References

docs/circa-spec.md sections 12.5, 6.1

Depends on: export execution.

## Context Spec section 12.5 asks for lossless preservation wherever practical. Family scans are often the only surviving copy of a photograph, and re-encoding them repeatedly degrades them permanently. ## Scope Lossless export option with optional archival masters alongside derivatives. ## Implementation notes - Where the export needs no pixel modification, copy bytes directly rather than decoding and re-encoding. Metadata-only changes should use a metadata-preserving write path. - If originals are already lossless, record that fact in the manifest. - Optionally emit archival masters alongside derivative JPEGs, for downstream compatibility without sacrificing the archival copy. - Make the trade-off explicit in the UI: output size against fidelity. Users exporting a large collection need to know what they are choosing. - Verify that a lossless path genuinely produced identical image data â€” compare decoded pixel data, not just file size, in tests. - Document which formats support which paths. ## Done when - [ ] Lossless export produces bit-identical image data where no pixel change is required - [ ] Already-lossless originals are recorded as such in the manifest - [ ] Archival masters can optionally accompany derivatives - [ ] The size/fidelity trade-off is visible in the UI - [ ] Losslessness is verified by test, not assumed ## References - `docs/circa-spec.md` sections 12.5, 6.1 Depends on: export execution.

claude-bot added this to the v0.5.0 milestone

2026-07-28 04:57:31 +00:00

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2026-07-28 04:57:31 +00:00