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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://misskey/users/9zc7n3iyztsj0001",
    "https://www.w3.org/ns/activitystreams#Public"
  ],
  "id": "http://pasture-one-actor/actor/Nc_ov9JixYI",
  "published": "2024-10-14T06:44:21Z",
  "object": {
    "type": "Note",
    "attributedTo": "http://pasture-one-actor/actor",
    "to": [
      "https://www.w3.org/ns/activitystreams#Public",
      "http://misskey/users/9zc7n3iyztsj0001"
    ],
    "id": "http://pasture-one-actor/actor/n8CvyBca-M8",
    "published": "2024-10-14T06:44:21Z",
    "content": "no description",
    "attachment": {
      "type": "Document",
      "url": "http://pasture-one-actor/images/100.png"
    }
  }
}
misskey
{
  "id": "9zc7qt8oa335000v",
  "createdAt": "2024-10-14T06:44:21.000Z",
  "userId": "9zc7oqlua3350002",
  "user": {
    "id": "9zc7oqlua3350002",
    "name": "Test Actor",
    "username": "actor",
    "host": "pasture-one-actor",
    "avatarUrl": "http://misskey/identicon/actor@pasture-one-actor",
    "avatarBlurhash": null,
    "avatarDecorations": [],
    "isBot": false,
    "isCat": false,
    "instance": {
      "name": null,
      "softwareName": null,
      "softwareVersion": null,
      "iconUrl": null,
      "faviconUrl": null,
      "themeColor": null
    },
    "emojis": {},
    "onlineStatus": "unknown"
  },
  "text": "no description",
  "cw": null,
  "visibility": "public",
  "localOnly": false,
  "reactionAcceptance": null,
  "renoteCount": 0,
  "repliesCount": 0,
  "reactionCount": 0,
  "reactions": {},
  "reactionEmojis": {},
  "emojis": {},
  "fileIds": [
    "9zc7qtr7a335000u"
  ],
  "files": [
    {
      "id": "9zc7qtr7a335000u",
      "createdAt": "2024-10-14T06:44:21.667Z",
      "name": "100.png",
      "type": "image/png",
      "md5": "99f3d0d6e579628f6a0381135c333ec8",
      "size": 0,
      "isSensitive": false,
      "blurhash": "e1IpV2}=fQ}=fQ}=j@fQj@fQfQfQfQfQfQ}=j@fQj@fQfQfQfQfQfQ",
      "properties": {
        "width": 40,
        "height": 40
      },
      "url": "http://pasture-one-actor/images/100.png",
      "thumbnailUrl": "http://pasture-one-actor/images/100.png",
      "comment": null,
      "folderId": null,
      "folder": null,
      "userId": "9zc7oqlua3350002",
      "user": null
    }
  ],
  "replyId": null,
  "renoteId": null,
  "uri": "http://pasture-one-actor/actor/n8CvyBca-M8",
  "clippedCount": 0
}

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://misskey/users/9zc7n3iyztsj0001",
    "https://www.w3.org/ns/activitystreams#Public"
  ],
  "id": "http://pasture-one-actor/actor/t5pBJUlM-NE",
  "published": "2024-10-14T06:44:22Z",
  "object": {
    "type": "Note",
    "attributedTo": "http://pasture-one-actor/actor",
    "to": [
      "https://www.w3.org/ns/activitystreams#Public",
      "http://misskey/users/9zc7n3iyztsj0001"
    ],
    "id": "http://pasture-one-actor/actor/-SmtWa_jIHM",
    "published": "2024-10-14T06:44:22Z",
    "content": "text",
    "attachment": {
      "type": "Document",
      "url": "http://pasture-one-actor/images/100.png",
      "name": "name",
      "summary": "summary",
      "content": "content"
    }
  }
}
misskey
{
  "id": "9zc7qu0ga335000x",
  "createdAt": "2024-10-14T06:44:22.000Z",
  "userId": "9zc7oqlua3350002",
  "user": {
    "id": "9zc7oqlua3350002",
    "name": "Test Actor",
    "username": "actor",
    "host": "pasture-one-actor",
    "avatarUrl": "http://misskey/identicon/actor@pasture-one-actor",
    "avatarBlurhash": null,
    "avatarDecorations": [],
    "isBot": false,
    "isCat": false,
    "instance": {
      "name": null,
      "softwareName": null,
      "softwareVersion": null,
      "iconUrl": null,
      "faviconUrl": null,
      "themeColor": null
    },
    "emojis": {},
    "onlineStatus": "unknown"
  },
  "text": "text",
  "cw": null,
  "visibility": "public",
  "localOnly": false,
  "reactionAcceptance": null,
  "renoteCount": 0,
  "repliesCount": 0,
  "reactionCount": 0,
  "reactions": {},
  "reactionEmojis": {},
  "emojis": {},
  "fileIds": [
    "9zc7qub1a335000w"
  ],
  "files": [
    {
      "id": "9zc7qub1a335000w",
      "createdAt": "2024-10-14T06:44:22.381Z",
      "name": "100.png",
      "type": "image/png",
      "md5": "beab44e1b686b380f998048d5610c7a0",
      "size": 0,
      "isSensitive": false,
      "blurhash": "e01NkZkvfQkvfQkvfRfQfRfQfQfQfQfQfQkvfRfQfRfQfQfQfQfQfQ",
      "properties": {
        "width": 40,
        "height": 40
      },
      "url": "http://pasture-one-actor/images/100.png",
      "thumbnailUrl": "http://pasture-one-actor/images/100.png",
      "comment": "name",
      "folderId": null,
      "folder": null,
      "userId": "9zc7oqlua3350002",
      "user": null
    }
  ],
  "replyId": null,
  "renoteId": null,
  "uri": "http://pasture-one-actor/actor/-SmtWa_jIHM",
  "clippedCount": 0
}

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://misskey/users/9zc7n3iyztsj0001",
    "https://www.w3.org/ns/activitystreams#Public"
  ],
  "id": "http://pasture-one-actor/actor/oQPrHnGwJyY",
  "published": "2024-10-14T06:44:22Z",
  "object": {
    "type": "Note",
    "attributedTo": "http://pasture-one-actor/actor",
    "to": [
      "https://www.w3.org/ns/activitystreams#Public",
      "http://misskey/users/9zc7n3iyztsj0001"
    ],
    "id": "http://pasture-one-actor/actor/IVrLqfX552w",
    "published": "2024-10-14T06:44:22Z",
    "content": "text",
    "attachment": [
      {
        "type": "Document",
        "url": "http://pasture-one-actor/assets/FediverseLogo.png",
        "name": "name",
        "imageType": "image/jpeg"
      }
    ]
  }
}
misskey
{
  "id": "9zc7qu0ga335000z",
  "createdAt": "2024-10-14T06:44:22.000Z",
  "userId": "9zc7oqlua3350002",
  "user": {
    "id": "9zc7oqlua3350002",
    "name": "Test Actor",
    "username": "actor",
    "host": "pasture-one-actor",
    "avatarUrl": "http://misskey/identicon/actor@pasture-one-actor",
    "avatarBlurhash": null,
    "avatarDecorations": [],
    "isBot": false,
    "isCat": false,
    "instance": {
      "name": null,
      "softwareName": null,
      "softwareVersion": null,
      "iconUrl": null,
      "faviconUrl": null,
      "themeColor": null
    },
    "emojis": {},
    "onlineStatus": "unknown"
  },
  "text": "text",
  "cw": null,
  "visibility": "public",
  "localOnly": false,
  "reactionAcceptance": null,
  "renoteCount": 0,
  "repliesCount": 0,
  "reactionCount": 0,
  "reactions": {},
  "reactionEmojis": {},
  "emojis": {},
  "fileIds": [
    "9zc7quvxa335000y"
  ],
  "files": [
    {
      "id": "9zc7quvxa335000y",
      "createdAt": "2024-10-14T06:44:23.133Z",
      "name": "FediverseLogo.png",
      "type": "image/png",
      "md5": "85e7feae66363e9e200570a28b0cf20a",
      "size": 0,
      "isSensitive": false,
      "blurhash": "eQE_?c.}4.YJM^}fi{EVw[xu9JK[M~xI-T9+TJRPX2$$E]NFo}j1tO",
      "properties": {
        "width": 1548,
        "height": 1548
      },
      "url": "http://pasture-one-actor/assets/FediverseLogo.png",
      "thumbnailUrl": "http://pasture-one-actor/assets/FediverseLogo.png",
      "comment": "name",
      "folderId": null,
      "folder": null,
      "userId": "9zc7oqlua3350002",
      "user": null
    }
  ],
  "replyId": null,
  "renoteId": null,
  "uri": "http://pasture-one-actor/actor/IVrLqfX552w",
  "clippedCount": 0
}

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://misskey/users/9zc7n3iyztsj0001",
    "https://www.w3.org/ns/activitystreams#Public"
  ],
  "id": "http://pasture-one-actor/actor/nShz-ubx-rw",
  "published": "2024-10-14T06:44:23Z",
  "object": {
    "type": "Note",
    "attributedTo": "http://pasture-one-actor/actor",
    "to": [
      "https://www.w3.org/ns/activitystreams#Public",
      "http://misskey/users/9zc7n3iyztsj0001"
    ],
    "id": "http://pasture-one-actor/actor/t6URM8PDGCw",
    "published": "2024-10-14T06:44:23Z",
    "content": "no comment in attachment",
    "attachment": [
      {
        "type": "Document",
        "url": "http://pasture-one-actor/assets/FediverseLogo.png"
      }
    ]
  }
}
misskey
{
  "id": "9zc7qus8a3350010",
  "createdAt": "2024-10-14T06:44:23.000Z",
  "userId": "9zc7oqlua3350002",
  "user": {
    "id": "9zc7oqlua3350002",
    "name": "Test Actor",
    "username": "actor",
    "host": "pasture-one-actor",
    "avatarUrl": "http://misskey/identicon/actor@pasture-one-actor",
    "avatarBlurhash": null,
    "avatarDecorations": [],
    "isBot": false,
    "isCat": false,
    "instance": {
      "name": null,
      "softwareName": null,
      "softwareVersion": null,
      "iconUrl": null,
      "faviconUrl": null,
      "themeColor": null
    },
    "emojis": {},
    "onlineStatus": "unknown"
  },
  "text": "no comment in attachment",
  "cw": null,
  "visibility": "public",
  "localOnly": false,
  "reactionAcceptance": null,
  "renoteCount": 0,
  "repliesCount": 0,
  "reactionCount": 0,
  "reactions": {},
  "reactionEmojis": {},
  "emojis": {},
  "fileIds": [
    "9zc7quvxa335000y"
  ],
  "files": [
    {
      "id": "9zc7quvxa335000y",
      "createdAt": "2024-10-14T06:44:23.133Z",
      "name": "FediverseLogo.png",
      "type": "image/png",
      "md5": "85e7feae66363e9e200570a28b0cf20a",
      "size": 0,
      "isSensitive": false,
      "blurhash": "eQE_?c.}4.YJM^}fi{EVw[xu9JK[M~xI-T9+TJRPX2$$E]NFo}j1tO",
      "properties": {
        "width": 1548,
        "height": 1548
      },
      "url": "http://pasture-one-actor/assets/FediverseLogo.png",
      "thumbnailUrl": "http://pasture-one-actor/assets/FediverseLogo.png",
      "comment": "name",
      "folderId": null,
      "folder": null,
      "userId": "9zc7oqlua3350002",
      "user": null
    }
  ],
  "replyId": null,
  "renoteId": null,
  "uri": "http://pasture-one-actor/actor/t6URM8PDGCw",
  "clippedCount": 0
}