Add thumbnails

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PapaTutuWawa 2022-02-27 15:32:06 +01:00
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# Custom XEPs
| Title | Description |
| --- | --- |
| Thumbnails | A specification for different types of thumbnails |
| File Upload Notifications | A specification for telling clients that a file will be sent as soon as it is uploaded |

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# Thumbnails
## 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).
This document specifies are more general and extensible element for specifiying thumbnails.
## Usage
```
<thumbnail type="blurhash" xmlns="urn:xmpp:thumbnail:0">
<payload>LEHV6nWB2yk8pyoJadR*.7kCMdnj</payload>
</thumbnail>
```
In this example, the thumbnail is specified of type `blurhash`, which means that a supporting
client should decode the `<payload/>` element using the [Blurhash](https://github.com/woltapp/blurhash) algorithm.
In order to enable a sort-of interoperability with [Jingle Content Thumbnails](https://xmpp.org/extensions/xep-0264.html), a type
`urn:xmpp:thumbs:0` is defined. If this is specified, then a supporting client must
interpret the child of the `<payload />` as an `<thumbnail />` element as specified by
:[Jingle Content Thumbnails](https://xmpp.org/extensions/xep-0264.html)
```
<thumbnail type="urn:xmpp:thumbs:1" xmlns="urn:xmpp:thumbnail:0">
<payload>
<thumbnail xmlns="urn:xmpp:thumbs:1" uri="..." media-type="image/png" width="128" height="96" />
</payload>
</thumbnail>
```
In the case of [Jingle Content Thumbnails](https://xmpp.org/extensions/xep-0264.html) compatibility,
the `<payload />` element must contain exactly one `<thumbnail xmlns="urn:xmpp:thumbs:1" />` element.
Other extensions may define similar types. Note that the content of the `<payload />` element
is dependent on the type specified in the `<thumbnail xmlns="urn:xmpp:thumbnail:0" />`
element.
### Thumbnail Types
#### Blurhash
If a sender specifies the type to be of `blurhash`, then the payload must contain the
image data as specified by the [Blurhash](https://github.com/woltapp/blurhash) algorithm. Care should be taken to prevent
the blurhash data from growing to large in order to prevent hitting the stanza size limit.
## Usage with Stateless Inline Media Sharing
NOTE: This example is taken from [Stateless Inline Media Sharing](https://xmpp.org/extensions/xep-0385.html) and modified for this protocol.
```
<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>
<thumbnail type="urn:xmpp:thumbs:1" xmlns='urn:xmpp:thumbnail:0'>
<payload>
<thumbnail xmlns='urn:xmpp:thumbs:1'uri='cid:sha1+ffd7c8d28e9c5e82afea41f97108c6b4@bob.xmpp.org' media-type='image/png' width='128' height='96'/>
</payload>
</thumbnail>
<thumbnail type="blurhash" xmlns='urn:xmpp:thumbnail:0'>
<payload>LEHV6nWB2yk8pyoJadR*.7kCMdnj</payload>
</thumbnail>
</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).