Enhance ActivityPub image attachments with width/height metadata (#17563)

* Initial plan

* enhance(backend): include image dimensions in AP attachments

* fix(backend): guard AP attachment dimension properties

* fix(changelog): move AP dimensions note to 2026.6.0

* Update CHANGELOG.md

---------

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: syuilo <4439005+syuilo@users.noreply.github.com>

packages/backend/src/core/activitypub/ApRendererService.ts

@@ -172,6 +172,8 @@ export class ApRendererService {
 			mediaType: file.webpublicType ?? file.type,
 			url: this.driveFileEntityService.getPublicUrl(file),
 			name: file.comment,
+			width: file.properties?.width,
+			height: file.properties?.height,
 			sensitive: file.isSensitive,
 		};
 	}

packages/backend/src/core/activitypub/type.ts

@@ -34,6 +34,8 @@ export interface IObject {
 	href?: string;
 	tag?: IObject | IObject[];
 	sensitive?: boolean;
+	width?: number;
+	height?: number;
 }
 
 /**

packages/backend/test/unit/activitypub.ts

@@ -15,6 +15,7 @@ import { Test } from '@nestjs/testing';
 import { MockResolver } from '../misc/mock-resolver.js';
 import type { IActor, IApDocument, ICollection, IObject, IPost } from '@/core/activitypub/type.js';
 import type { MiRemoteUser } from '@/models/User.js';
+import type { MiDriveFile } from '@/models/DriveFile.js';
 import { ApImageService } from '@/core/activitypub/models/ApImageService.js';
 import { ApNoteService } from '@/core/activitypub/models/ApNoteService.js';
 import { ApPersonService } from '@/core/activitypub/models/ApPersonService.js';
@@ -399,6 +400,28 @@ describe('ActivityPub', () => {
 	});
 
 	describe('Images', () => {
+		test('Render image document with dimensions', () => {
+			const rendered = rendererService.renderDocument({
+				id: genAidx(Date.now()),
+				type: 'image/png',
+				webpublicType: null,
+				url: 'https://example.test/files/image.png',
+				webpublicUrl: null,
+				comment: null,
+				isSensitive: false,
+				properties: { width: 3600, height: 1890 },
+				uri: null,
+				userHost: null,
+				isLink: false,
+				webpublicAccessKey: null,
+			} as MiDriveFile);
+
+			assert.strictEqual(rendered.type, 'Document');
+			assert.strictEqual(rendered.mediaType, 'image/png');
+			assert.strictEqual(rendered.width, 3600);
+			assert.strictEqual(rendered.height, 1890);
+		});
+
 		test('Create images', async () => {
 			const imageObject: IApDocument = {
 				type: 'Document',