Add ThumbHash support for image placeholders #3429
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Add ThumbHash library for compact image placeholders. ThumbHash offers advantages over BlurHash: - Better detail preservation - Embedded aspect ratio information - Alpha channel (transparency) support - More accurate color representation Source: https://github.com/evanw/thumbhash (MIT License) Closes damus-io#3427 Signed-off-by: alltheseas 🤖 Generated with [Claude Code](https://claude.com/claude-code) Co-Authored-By: Claude Opus 4.5 <[email protected]>
- Add thumbhash field to ImageMetadata struct - Update decode_image_metadata() to parse thumbhash from imeta tags - Update image_metadata_to_tag() to include thumbhash in output - Add process_thumbhash() to decode base64 thumbhash to UIImage - Add process_placeholder() helper that prefers thumbhash over blurhash - Update process_image_metadatas() to use process_placeholder() This enables displaying ThumbHash placeholders from other clients while maintaining backwards compatibility with BlurHash. Closes damus-io#3427 Signed-off-by: alltheseas 🤖 Generated with [Claude Code](https://claude.com/claude-code) Co-Authored-By: Claude Opus 4.5 <[email protected]>
- Add calculate_thumbhash() function for encoding UIImage to base64 hash - Update calculate_image_metadata() to use thumbhash parameter - Update PostView.handle_upload() to use calculate_thumbhash() Uploaded images now include thumbhash in their imeta tags, providing better quality placeholders for other clients. Closes damus-io#3427 Signed-off-by: alltheseas 🤖 Generated with [Claude Code](https://claude.com/claude-code) Co-Authored-By: Claude Opus 4.5 <[email protected]>
Add ThumbHash.swift to the following targets: - damus - HighlighterActionExtension - ShareExtension Closes damus-io#3427 Signed-off-by: alltheseas 🤖 Generated with [Claude Code](https://claude.com/claude-code) Co-Authored-By: Claude Opus 4.5 <[email protected]>
- Add 5 unit tests for ThumbHash functionality: - testThumbHashEncodeDecodeRoundtrip - testThumbHashBase64Roundtrip - testImageMetadataWithThumbHash - testImageMetadataWithBothHashes - testImageMetadataToTagWithThumbHash - Fix ImageMetaProcessState type name (was ImageMetadataProcessState) Closes damus-io#3427 Signed-off-by: alltheseas 🤖 Generated with [Claude Code](https://claude.com/claude-code) Co-Authored-By: Claude Opus 4.5 <[email protected]>
Calculate both placeholder hashes concurrently during image upload: - thumbhash: better quality, aspect ratio, alpha (newer clients) - blurhash: backwards compatibility with existing Nostr clients Both hashes are computed in parallel with the upload, so there's minimal additional latency. The imeta tag now includes both: thumbhash <base64> blurhash <string> Closes damus-io#3427 Signed-off-by: alltheseas 🤖 Generated with [Claude Code](https://claude.com/claude-code) Co-Authored-By: Claude Opus 4.5 <[email protected]>
danieldaquino
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Even if thumbhash might be better in some ways, blurhash is more widely supported around Nostr protocols (https://github.com/search?q=repo%3Anostr-protocol%2Fnips+blurhash&type=code). I have not seen references to thumbhash in the Nostr protocol specs (https://github.com/search?q=repo%3Anostr-protocol%2Fnips+thumbhash&type=code). @alltheseas, do other Nostr clients support thumbhash? |
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Fevela, and nostria |
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Summary
Add ThumbHash support for compact image placeholders. ThumbHash offers advantages over BlurHash:
Implementation:
Checklist
Standard PR Checklist
Closes:orFixes:tags in the commit messages wherever applicable, or made sure those are not needed. See Submitting patchesTest report
Device: iPhone 15 Pro Simulator
iOS: 17.5
Damus: master + this PR
Setup: Unit tests for encode/decode roundtrip
Steps:
xcodebuild test -only-testing:damusTests/ImageMetadataTestResults:
testThumbHashEncodeDecodeRoundtrip✅testThumbHashBase64Roundtrip✅testImageMetadataWithThumbHash✅testImageMetadataWithBothHashes✅testImageMetadataToTagWithThumbHash✅testImageMetadataToTagWithBothHashes✅testRemoveGPSData✅Other notes
Commits:
thumbhash: add ThumbHash implementation- MIT-licensed implementation from evanw/thumbhashthumbhash: add decoding support to ImageMetadata- Parse and decode thumbhash from imeta tagsthumbhash: use ThumbHash for encoding uploaded images- Encode with thumbhash on uploadthumbhash: add ThumbHash.swift to Xcode project- Add to damus, HighlighterActionExtension, ShareExtension targetsthumbhash: add unit tests and fix type name- 7 unit teststhumbhash: encode both thumbhash AND blurhash for compatibility- Backwards compat with existing clientsReferences: