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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": [
    "http://mitra/users/admin",
    "https://www.w3.org/ns/activitystreams#Public"
  ],
  "id": "http://pasture-one-actor/actor/-sCXljcz2LU",
  "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/4i8Cl_xNMys",
    "published": "2024-08-14T10:18:06Z",
    "content": "no description",
    "attachment": {
      "type": "Document",
      "url": "http://pasture-one-actor/images/100.png"
    }
  }
}
mitra
{
  "id": "01915065-16b7-c706-90a6-2f43dc385fcc",
  "uri": "http://pasture-one-actor/actor/4i8Cl_xNMys",
  "url": null,
  "created_at": "2024-08-14T10:18:06Z",
  "edited_at": null,
  "account": {
    "id": "01915063-5d13-9e38-ee07-83619d956ac4",
    "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": "2024-08-14T10:16:14.867539Z",
    "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": "01915065-16b3-47b6-fd59-d4ec45a42e87",
      "type": "image",
      "url": "http://mitra/media/f40dd2e84c1094fdabfa5658d10bf798c22a3f31e63488dd70f4ebebf0751635.png",
      "preview_url": "http://mitra/media/f40dd2e84c1094fdabfa5658d10bf798c22a3f31e63488dd70f4ebebf0751635.png",
      "description": null
    }
  ],
  "mentions": [
    {
      "id": "01915062-5a32-ede5-d7a2-c4be34515e6a",
      "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": [
    "http://mitra/users/admin",
    "https://www.w3.org/ns/activitystreams#Public"
  ],
  "id": "http://pasture-one-actor/actor/Kc076Ts_4Y4",
  "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/py6f-3yI4qM",
    "published": "2024-08-14T10:18:08Z",
    "content": "text",
    "attachment": {
      "type": "Document",
      "url": "http://pasture-one-actor/images/100.png",
      "name": "name",
      "summary": "summary",
      "content": "content"
    }
  }
}
mitra
{
  "id": "01915065-1c90-37c1-4791-036b36d9942b",
  "uri": "http://pasture-one-actor/actor/py6f-3yI4qM",
  "url": null,
  "created_at": "2024-08-14T10:18:08Z",
  "edited_at": null,
  "account": {
    "id": "01915063-5d13-9e38-ee07-83619d956ac4",
    "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": "2024-08-14T10:16:14.867539Z",
    "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": "01915065-1c8d-0f8a-e80d-8336cf11d51c",
      "type": "image",
      "url": "http://mitra/media/fee7241b2cd73bb832f50052135fe3c83e7c6f3694dfd28efa4296b2a29287c3.png",
      "preview_url": "http://mitra/media/fee7241b2cd73bb832f50052135fe3c83e7c6f3694dfd28efa4296b2a29287c3.png",
      "description": "name"
    }
  ],
  "mentions": [
    {
      "id": "01915062-5a32-ede5-d7a2-c4be34515e6a",
      "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": [
    "http://mitra/users/admin",
    "https://www.w3.org/ns/activitystreams#Public"
  ],
  "id": "http://pasture-one-actor/actor/rpYIfxmJVhk",
  "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/ytt6VJ0CtTo",
    "published": "2024-08-14T10:18:09Z",
    "content": "text",
    "attachment": [
      {
        "type": "Document",
        "url": "http://pasture-one-actor/assets/FediverseLogo.png",
        "name": "name",
        "imageType": "image/jpeg"
      }
    ]
  }
}
mitra
{
  "id": "01915065-2293-6628-e1e9-e83ead6c4d16",
  "uri": "http://pasture-one-actor/actor/ytt6VJ0CtTo",
  "url": null,
  "created_at": "2024-08-14T10:18:09Z",
  "edited_at": null,
  "account": {
    "id": "01915063-5d13-9e38-ee07-83619d956ac4",
    "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": "2024-08-14T10:16:14.867539Z",
    "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": "01915065-228e-cc9f-50ae-7cd7b5776cfc",
      "type": "image",
      "url": "http://mitra/media/2d7a61d31393a44edf2a30160cdd70b3582a4f97d5b550f8141dfee1641b4ae7.png",
      "preview_url": "http://mitra/media/2d7a61d31393a44edf2a30160cdd70b3582a4f97d5b550f8141dfee1641b4ae7.png",
      "description": "name"
    }
  ],
  "mentions": [
    {
      "id": "01915062-5a32-ede5-d7a2-c4be34515e6a",
      "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": [
    "http://mitra/users/admin",
    "https://www.w3.org/ns/activitystreams#Public"
  ],
  "id": "http://pasture-one-actor/actor/z2pysoVIOwE",
  "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/rxFIJr2irVk",
    "published": "2024-08-14T10:18:11Z",
    "content": "no comment in attachment",
    "attachment": [
      {
        "type": "Document",
        "url": "http://pasture-one-actor/assets/FediverseLogo.png"
      }
    ]
  }
}
mitra
{
  "id": "01915065-285d-fbb3-ce5c-5eeeef3e2a93",
  "uri": "http://pasture-one-actor/actor/rxFIJr2irVk",
  "url": null,
  "created_at": "2024-08-14T10:18:11Z",
  "edited_at": null,
  "account": {
    "id": "01915063-5d13-9e38-ee07-83619d956ac4",
    "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": "2024-08-14T10:16:14.867539Z",
    "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": "01915065-2859-ea40-4dcc-4951e13d0ba0",
      "type": "image",
      "url": "http://mitra/media/2d7a61d31393a44edf2a30160cdd70b3582a4f97d5b550f8141dfee1641b4ae7.png",
      "preview_url": "http://mitra/media/2d7a61d31393a44edf2a30160cdd70b3582a4f97d5b550f8141dfee1641b4ae7.png",
      "description": null
    }
  ],
  "mentions": [
    {
      "id": "01915062-5a32-ede5-d7a2-c4be34515e6a",
      "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": []
}