Diocrafts
96 lines
2.5 KiB
Markdown
96 lines
2.5 KiB
Markdown
# Thumbnails and Transcoding
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OxiCloud optimizes image delivery with two complementary features:
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- WebP thumbnail generation in three sizes
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- On-the-fly image transcoding for browsers that advertise WebP support
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Both features use a memory cache plus a persistent disk cache and are designed to stay off the request hot path whenever possible.
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## Thumbnails
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### Supported sizes
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| Size | Dimensions | Directory |
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| --- | --- | --- |
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| `icon` | 150 x 150 | `.thumbnails/icon/` |
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| `preview` | 400 x 400 | `.thumbnails/preview/` |
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| `large` | 800 x 800 | `.thumbnails/large/` |
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### Supported inputs
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`image/jpeg`, `image/jpg`, `image/png`, `image/gif`, and `image/webp`
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All thumbnail outputs are stored as WebP.
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### API
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| Method | Path | Description |
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| --- | --- | --- |
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| `GET` | `/api/files/{id}/thumbnail/{size}` | Fetch a thumbnail |
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| `POST` | `/api/files/upload` | Upload a file and pre-generate thumbnails for supported images |
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Thumbnail responses include:
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- `Content-Type: image/webp`
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- `Cache-Control: public, max-age=31536000, immutable`
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- `ETag: "thumb-{id}-{size}"`
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### Generation flow
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1. Upload succeeds through the file API
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2. If the MIME type is supported, OxiCloud starts thumbnail generation in a background task
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3. If a thumbnail is requested before pre-generation completes, the request can generate it lazily
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4. Future requests are served from memory or disk cache
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## Image Transcoding
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OxiCloud can serve a smaller WebP version of uploaded JPEG, PNG, or GIF files when the client advertises WebP support in the `Accept` header.
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### Rules
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- Files over 5 MB skip transcoding
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- Existing WebP files are not transcoded again
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- SVG and BMP are not transcoded
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- If the WebP output is larger than the original, OxiCloud serves the original file instead
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### Storage layout
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```text
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<storage_path>/
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.transcoded/
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webp/
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<file_id>.webp
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```
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### Statistics tracked by the service
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- Cache hits
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- Disk hits
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- Successful transcodes
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- Bytes saved
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- Transcode errors
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## Caching
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Both thumbnail and transcode services use:
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- An in-memory LRU cache for hot assets
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- A disk cache for persistent reuse across restarts
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- Fire-and-forget background writes for cache warmup
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For the broader cache model across metadata and listings, see [Caching Architecture](/architecture/caching).
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## Example
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```text
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Client: GET /api/files/abc-123/download
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Accept: image/webp, image/png, */*
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Server: checks cache -> transcodes if needed -> returns the smaller asset
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```
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## Related Pages
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- [Caching Architecture](/architecture/caching)
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- [ZIP and Compression](/guide/zip-and-compression) |