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# Extensible File Thumbnails
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## Introduction
When sending media, it is often helpful for users when a thumbnail can be shown before the
actual file is finished downloading.
XMPP already has a protocol for specifying thumbails, [Jingle Content Thumbnails ](https://xmpp.org/extensions/xep-0264.html ).
However, this protocol requires that the thumbnail is a base64-encoded image published using
[Bits of Binary ](https://xmpp.org/extensions/xep-0231.html ). This prevents clients from implementing newer technologies, such as
[Blurhash ](https://github.com/woltapp/blurhash ).
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This document specifies are more general and extensible element for specifiying thumbnails in various formats.
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## Usage
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```xml
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< file-thumbnails xmlns = "proto:urn:xmpp:eft:0" >
< blurhash xmlns = "proto:urn:xmpp:eft:blurhash" > LEHV6nWB2yk8pyoJadR*.7kCMdnj< / blurhash >
< / file-thumbnails >
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```
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In this example, the thumbnail contains only a blurhash thumbnail, indicated by the `<blurhash/>` element, but an implementation
may add more versions of the same thumbnail, i.e. another `<base64-bob/>` element as a fallback if a client does not support
blurhash. To prevent confusion in the display of a thumbnail, all children of `<file-thumbnail />` must describe a thumbnail
for the same file.
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### Thumbnail Types
#### Blurhash
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If a sender includes a `<blurhash/>` inside the `<file-thumbnail/>` element, then it must be interpreted as
[Blurhash ](https://github.com/woltapp/blurhash ) data. As a sender, care must be taken to not make the Blurhash
thumbnail too big as to not loose the advantages of blurhash.
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```xml
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< file-thumbails xmlns = "proto:urn:xmpp:eft:0" >
< blurhash xmlns = "proto:urn:xmpp:eft:blurhash" > LEHV6nWB2yk8pyoJadR*.7kCMdnj< / blurhash >
< / file-thumbnails >
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```
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#### Jingle Content Thumbnail Compatability
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In order to enable a pseudo-interoperability with [Jingle Content Thumbnails ](https://xmpp.org/extensions/xep-0264.html ), inclusion of a
`<thumbnail/>` element is allowed. This is to allow easy reuse of an already existent [Jingle Content Thumbnails ](https://xmpp.org/extensions/xep-0264.html )
implementation.
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```xml
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< file-thumbails xmlns = "proto:urn:xmpp:eft:0" type = "base64-bob" >
< thumbnail xmlns = "urn:xmpp:thumbs:1" uri = "cid:sha1+...@bob.xmpp.org" media-type = "image/png" width = "128" height = "96" / >
< / file-thumbnails >
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```
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## Usage Example with Stateless Inline Media Sharing
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NOTE: This example is taken from [Stateless Inline Media Sharing ](https://xmpp.org/extensions/xep-0385.html ) and modified for this protocol.
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```xml
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< message to = 'julient@shakespeare.lit' from = 'romeo@montague.lit' >
< body > Look at the nice view from the summit.< / body >
< reference xmlns = 'urn:xmpp:reference:0' begin = '17' end = '20' type = 'data' >
< media-sharing xmlns = 'urn:xmpp:sims:1' >
< file xmlns = 'urn:xmpp:jingle:apps:file-transfer:5' >
< media-type > image/jpeg< / media-type >
< name > summit.jpg< / name >
< size > 3032449< / size >
< hash xmlns = 'urn:xmpp:hashes:2' algo = 'sha3-256' > 2XarmwTlNxDAMkvymloX3S5+VbylNrJt/l5QyPa+YoU=< / hash >
< hash xmlns = 'urn:xmpp:hashes:2' algo = 'id-blake2b256' > 2AfMGH8O7UNPTvUVAM9aK13mpCY=< / hash >
< desc > Photo from the summit.< / desc >
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< file-thumbnail type = "base64-bob" xmlns = 'urn:xmpp:thumbnail:0' >
< base64-bob uri = "cid:sha1+ffd7c8d28e9c5e82afea41f97108c6b4@bob.xmpp.org" media-type = "image/png" width = "128" height = "96" / >
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< / thumbnail >
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< file-thumbnails xmlns = "proto:urn:xmpp:eft:0" >
< blurhash xmlns = "proto:urn:xmpp:eft:blurhash" > LEHV6nWB2yk8pyoJadR*.7kCMdnj< / blurhash >
< thumbnail xmlns = 'urn:xmpp:thumbs:1'
uri='cid:sha1+ffd7c8d28e9c5e82afea41f97108c6b4@bob.xmpp.org'
media-type='image/png'
width='128'
height='96'/>
< / file-thumbnails >
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< / file >
< sources >
< reference xmlns = 'urn:xmpp:reference:0' type = 'data' uri = 'https://download.montague.lit/4a771ac1-f0b2-4a4a-9700-f2a26fa2bb67/summit.jpg' / >
< reference xmlns = 'urn:xmpp:reference:0' type = 'data' uri = 'xmpp:romeo@montague.lit/resource?jingle;id=9559976B-3FBF-4E7E-B457-2DAA225972BB' / >
< / sources >
< / media-sharing >
< / reference >
< / message >
```
## Security Considerations
The same considerations apply as specified by [Jingle Content Thumbnails ](https://xmpp.org/extensions/xep-0264.html ).
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## Todo
- Change XML namespace from `proto:urn:xmpp:eft:0` to `urn:xmpp:eft:0` once accepted as an experimental XEP
## Changelog
### 0.1.0
- Remove the base64 thumbnail type
- Namespace all thumbnail types
- Remove the type attribute of < file-thumbnail />
- Rename < file-thumbnail /> to < file-thumbnails />
- Rename the namespace from file-thumbnails to eft
- Rename from File Thumbnails to Extensible File Thumbnails
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## Info
| Key | Value |
| --- | --- |
| Author | PapaTutuWawa |
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| Version | 0.1.0 |
| Short name | eft |
