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Image Description

The Image type is defined in ActivityStreams Vocabulary.

In this support table, we only consider how the image description, commonly called AltText is handled. Image descriptions are important from an accessibility standpoint, see WCAG 2.2. Text Alternatives.

It seems that certain implementations, e.g. firefish, store the image description on a per image URL basis and not for every instance of an image reference.

Examples

Example 1

activity
{
  "@context": [
    "https://www.w3.org/ns/activitystreams",
    {
      "Hashtag": "as:Hashtag",
      "sensitive": "as:sensitive"
    }
  ],
  "type": "Create",
  "actor": "http://pasture-one-actor/actor",
  "to": [
    "https://www.w3.org/ns/activitystreams#Public",
    "http://mitra/users/admin"
  ],
  "id": "http://pasture-one-actor/actor/jV5L4G3yCCU",
  "object": {
    "type": "Note",
    "attributedTo": "http://pasture-one-actor/actor",
    "to": [
      "https://www.w3.org/ns/activitystreams#Public",
      "http://mitra/users/admin"
    ],
    "id": "http://pasture-one-actor/actor/AHd4Ts2vsW0",
    "published": "2024-08-03T15:44:04Z",
    "content": "no description",
    "attachment": {
      "type": "Document",
      "url": "http://pasture-one-actor/images/100.png"
    }
  }
}
mitra
{
  "id": "019118e9-8ef2-c033-b488-898d90f4783d",
  "uri": "http://pasture-one-actor/actor/AHd4Ts2vsW0",
  "url": null,
  "created_at": "2024-08-03T15:44:04Z",
  "edited_at": null,
  "account": {
    "id": "019118e7-ded9-7460-3eab-e229fb6ef7d0",
    "username": "actor",
    "acct": "actor@pasture-one-actor",
    "actor_id": "http://pasture-one-actor/actor",
    "url": "http://pasture-one-actor/actor",
    "display_name": "Test Actor",
    "created_at": "2024-08-03T15:42:14.744767Z",
    "note": "",
    "avatar": null,
    "header": null,
    "locked": false,
    "mention_policy": "none",
    "bot": false,
    "identity_proofs": [],
    "payment_options": [],
    "fields": [],
    "emojis": [],
    "followers_count": 0,
    "following_count": 0,
    "subscribers_count": 0,
    "statuses_count": 23,
    "source": null,
    "role": null,
    "authentication_methods": null,
    "client_config": null
  },
  "content": "no description",
  "in_reply_to_id": null,
  "in_reply_to_account_id": null,
  "reblog": null,
  "visibility": "public",
  "sensitive": false,
  "spoiler_text": "",
  "pinned": false,
  "replies_count": 0,
  "favourites_count": 0,
  "reblogs_count": 0,
  "media_attachments": [
    {
      "id": "019118e9-8eef-fc4b-6837-0eac499b1c66",
      "type": "image",
      "url": "http://mitra/media/002b761fd30d6fd065e37e4ed16de7099a4ab0ee597f743b47b73d8fb1274dbd.png",
      "preview_url": "http://mitra/media/002b761fd30d6fd065e37e4ed16de7099a4ab0ee597f743b47b73d8fb1274dbd.png",
      "description": null
    }
  ],
  "mentions": [
    {
      "id": "019118e6-d690-71d3-ff0d-fec253e88c18",
      "username": "admin",
      "acct": "admin",
      "url": "http://mitra/users/admin"
    }
  ],
  "tags": [],
  "emojis": [],
  "favourited": false,
  "reblogged": false,
  "pleroma": {
    "emoji_reactions": [],
    "in_reply_to_account_acct": null,
    "quote": null,
    "quote_visible": false
  },
  "ipfs_cid": null,
  "links": []
}

Example 2

activity
{
  "@context": [
    "https://www.w3.org/ns/activitystreams",
    {
      "Hashtag": "as:Hashtag",
      "sensitive": "as:sensitive"
    }
  ],
  "type": "Create",
  "actor": "http://pasture-one-actor/actor",
  "to": [
    "https://www.w3.org/ns/activitystreams#Public",
    "http://mitra/users/admin"
  ],
  "id": "http://pasture-one-actor/actor/EG2djaIvX4s",
  "object": {
    "type": "Note",
    "attributedTo": "http://pasture-one-actor/actor",
    "to": [
      "https://www.w3.org/ns/activitystreams#Public",
      "http://mitra/users/admin"
    ],
    "id": "http://pasture-one-actor/actor/2Yb2VU2Yujw",
    "published": "2024-08-03T15:44:05Z",
    "content": "text",
    "attachment": {
      "type": "Document",
      "url": "http://pasture-one-actor/images/100.png",
      "name": "name",
      "summary": "summary",
      "content": "content"
    }
  }
}
mitra
{
  "id": "019118e9-94d1-392c-7aa1-d9db30f562a5",
  "uri": "http://pasture-one-actor/actor/2Yb2VU2Yujw",
  "url": null,
  "created_at": "2024-08-03T15:44:05Z",
  "edited_at": null,
  "account": {
    "id": "019118e7-ded9-7460-3eab-e229fb6ef7d0",
    "username": "actor",
    "acct": "actor@pasture-one-actor",
    "actor_id": "http://pasture-one-actor/actor",
    "url": "http://pasture-one-actor/actor",
    "display_name": "Test Actor",
    "created_at": "2024-08-03T15:42:14.744767Z",
    "note": "",
    "avatar": null,
    "header": null,
    "locked": false,
    "mention_policy": "none",
    "bot": false,
    "identity_proofs": [],
    "payment_options": [],
    "fields": [],
    "emojis": [],
    "followers_count": 0,
    "following_count": 0,
    "subscribers_count": 0,
    "statuses_count": 24,
    "source": null,
    "role": null,
    "authentication_methods": null,
    "client_config": null
  },
  "content": "text",
  "in_reply_to_id": null,
  "in_reply_to_account_id": null,
  "reblog": null,
  "visibility": "public",
  "sensitive": false,
  "spoiler_text": "",
  "pinned": false,
  "replies_count": 0,
  "favourites_count": 0,
  "reblogs_count": 0,
  "media_attachments": [
    {
      "id": "019118e9-94c8-893d-47b3-125a8828e98b",
      "type": "image",
      "url": "http://mitra/media/dc238c09d4880ea5b6fcad6adb887f0f51d25725bcfb9141477f3f98f775edaf.png",
      "preview_url": "http://mitra/media/dc238c09d4880ea5b6fcad6adb887f0f51d25725bcfb9141477f3f98f775edaf.png",
      "description": "name"
    }
  ],
  "mentions": [
    {
      "id": "019118e6-d690-71d3-ff0d-fec253e88c18",
      "username": "admin",
      "acct": "admin",
      "url": "http://mitra/users/admin"
    }
  ],
  "tags": [],
  "emojis": [],
  "favourited": false,
  "reblogged": false,
  "pleroma": {
    "emoji_reactions": [],
    "in_reply_to_account_acct": null,
    "quote": null,
    "quote_visible": false
  },
  "ipfs_cid": null,
  "links": []
}

Example 3

activity
{
  "@context": [
    "https://www.w3.org/ns/activitystreams",
    {
      "Hashtag": "as:Hashtag",
      "sensitive": "as:sensitive"
    }
  ],
  "type": "Create",
  "actor": "http://pasture-one-actor/actor",
  "to": [
    "https://www.w3.org/ns/activitystreams#Public",
    "http://mitra/users/admin"
  ],
  "id": "http://pasture-one-actor/actor/RNvlHziA0EI",
  "object": {
    "type": "Note",
    "attributedTo": "http://pasture-one-actor/actor",
    "to": [
      "https://www.w3.org/ns/activitystreams#Public",
      "http://mitra/users/admin"
    ],
    "id": "http://pasture-one-actor/actor/V2J2iKGEOXM",
    "published": "2024-08-03T15:44:07Z",
    "content": "text",
    "attachment": [
      {
        "type": "Document",
        "url": "http://pasture-one-actor/assets/FediverseLogo.png",
        "name": "name",
        "imageType": "image/jpeg"
      }
    ]
  }
}
mitra
{
  "id": "019118e9-9ac1-4d4e-d304-ea2a32e8cffc",
  "uri": "http://pasture-one-actor/actor/V2J2iKGEOXM",
  "url": null,
  "created_at": "2024-08-03T15:44:07Z",
  "edited_at": null,
  "account": {
    "id": "019118e7-ded9-7460-3eab-e229fb6ef7d0",
    "username": "actor",
    "acct": "actor@pasture-one-actor",
    "actor_id": "http://pasture-one-actor/actor",
    "url": "http://pasture-one-actor/actor",
    "display_name": "Test Actor",
    "created_at": "2024-08-03T15:42:14.744767Z",
    "note": "",
    "avatar": null,
    "header": null,
    "locked": false,
    "mention_policy": "none",
    "bot": false,
    "identity_proofs": [],
    "payment_options": [],
    "fields": [],
    "emojis": [],
    "followers_count": 0,
    "following_count": 0,
    "subscribers_count": 0,
    "statuses_count": 25,
    "source": null,
    "role": null,
    "authentication_methods": null,
    "client_config": null
  },
  "content": "text",
  "in_reply_to_id": null,
  "in_reply_to_account_id": null,
  "reblog": null,
  "visibility": "public",
  "sensitive": false,
  "spoiler_text": "",
  "pinned": false,
  "replies_count": 0,
  "favourites_count": 0,
  "reblogs_count": 0,
  "media_attachments": [
    {
      "id": "019118e9-9aba-511a-002d-cb7a0ad7ada5",
      "type": "image",
      "url": "http://mitra/media/2d7a61d31393a44edf2a30160cdd70b3582a4f97d5b550f8141dfee1641b4ae7.png",
      "preview_url": "http://mitra/media/2d7a61d31393a44edf2a30160cdd70b3582a4f97d5b550f8141dfee1641b4ae7.png",
      "description": "name"
    }
  ],
  "mentions": [
    {
      "id": "019118e6-d690-71d3-ff0d-fec253e88c18",
      "username": "admin",
      "acct": "admin",
      "url": "http://mitra/users/admin"
    }
  ],
  "tags": [],
  "emojis": [],
  "favourited": false,
  "reblogged": false,
  "pleroma": {
    "emoji_reactions": [],
    "in_reply_to_account_acct": null,
    "quote": null,
    "quote_visible": false
  },
  "ipfs_cid": null,
  "links": []
}

Example 4

activity
{
  "@context": [
    "https://www.w3.org/ns/activitystreams",
    {
      "Hashtag": "as:Hashtag",
      "sensitive": "as:sensitive"
    }
  ],
  "type": "Create",
  "actor": "http://pasture-one-actor/actor",
  "to": [
    "https://www.w3.org/ns/activitystreams#Public",
    "http://mitra/users/admin"
  ],
  "id": "http://pasture-one-actor/actor/7bgKNuEN2oM",
  "object": {
    "type": "Note",
    "attributedTo": "http://pasture-one-actor/actor",
    "to": [
      "https://www.w3.org/ns/activitystreams#Public",
      "http://mitra/users/admin"
    ],
    "id": "http://pasture-one-actor/actor/Hp-0bCj7cF8",
    "published": "2024-08-03T15:44:08Z",
    "content": "no comment in attachment",
    "attachment": [
      {
        "type": "Document",
        "url": "http://pasture-one-actor/assets/FediverseLogo.png"
      }
    ]
  }
}
mitra
{
  "id": "019118e9-a09e-ca80-2b95-76137343222d",
  "uri": "http://pasture-one-actor/actor/Hp-0bCj7cF8",
  "url": null,
  "created_at": "2024-08-03T15:44:08Z",
  "edited_at": null,
  "account": {
    "id": "019118e7-ded9-7460-3eab-e229fb6ef7d0",
    "username": "actor",
    "acct": "actor@pasture-one-actor",
    "actor_id": "http://pasture-one-actor/actor",
    "url": "http://pasture-one-actor/actor",
    "display_name": "Test Actor",
    "created_at": "2024-08-03T15:42:14.744767Z",
    "note": "",
    "avatar": null,
    "header": null,
    "locked": false,
    "mention_policy": "none",
    "bot": false,
    "identity_proofs": [],
    "payment_options": [],
    "fields": [],
    "emojis": [],
    "followers_count": 0,
    "following_count": 0,
    "subscribers_count": 0,
    "statuses_count": 26,
    "source": null,
    "role": null,
    "authentication_methods": null,
    "client_config": null
  },
  "content": "no comment in attachment",
  "in_reply_to_id": null,
  "in_reply_to_account_id": null,
  "reblog": null,
  "visibility": "public",
  "sensitive": false,
  "spoiler_text": "",
  "pinned": false,
  "replies_count": 0,
  "favourites_count": 0,
  "reblogs_count": 0,
  "media_attachments": [
    {
      "id": "019118e9-a097-be77-518d-e68e352fcd34",
      "type": "image",
      "url": "http://mitra/media/2d7a61d31393a44edf2a30160cdd70b3582a4f97d5b550f8141dfee1641b4ae7.png",
      "preview_url": "http://mitra/media/2d7a61d31393a44edf2a30160cdd70b3582a4f97d5b550f8141dfee1641b4ae7.png",
      "description": null
    }
  ],
  "mentions": [
    {
      "id": "019118e6-d690-71d3-ff0d-fec253e88c18",
      "username": "admin",
      "acct": "admin",
      "url": "http://mitra/users/admin"
    }
  ],
  "tags": [],
  "emojis": [],
  "favourited": false,
  "reblogged": false,
  "pleroma": {
    "emoji_reactions": [],
    "in_reply_to_account_acct": null,
    "quote": null,
    "quote_visible": false
  },
  "ipfs_cid": null,
  "links": []
}