Add EXIF metadata support for image attachments

.github/changelog/2751-from-description

@@ -0,0 +1,4 @@
+Significance: patch
+Type: added
+
+Add EXIF metadata support for image attachments using Vernissage namespace.

includes/activity/class-base-object.php

@@ -121,6 +121,8 @@ class Base_Object extends Generic_Object {
 			'sensitive'         => 'as:sensitive',
 			'dcterms'           => 'http://purl.org/dc/terms/',
 			'gts'               => 'https://gotosocial.org/ns#',
+			'photos'            => 'https://joinvernissage.org/ns#',
+			'exif'              => 'photos:exif',
 			'interactionPolicy' => array(
 				'@id'   => 'gts:interactionPolicy',
 				'@type' => '@id',

includes/transformer/class-base.php

@@ -524,6 +524,12 @@ protected function transform_attachment( $media ) {
 						}
 					}
 
+					// Add EXIF metadata using the Vernissage namespace.
+					$exif = $this->get_exif_data( $id );
+					if ( $exif ) {
+						$image['exif'] = $exif;
+					}
+
 					$attachment = $image;
 				}
 				break;
@@ -591,6 +597,70 @@ protected function get_attachment_image_src( $id, $image_size = 'large' ) {
 		return $image;
 	}
 
+	/**
+	 * Get EXIF metadata for an image attachment using the Vernissage namespace.
+	 *
+	 * @link https://joinvernissage.org/ns#exif
+	 *
+	 * @param int $attachment_id The attachment ID.
+	 *
+	 * @return array|null EXIF data object or null if no EXIF data available.
+	 */
+	protected function get_exif_data( $attachment_id ) {
+		$metadata = \wp_get_attachment_metadata( $attachment_id );
+
+		if ( empty( $metadata['image_meta'] ) ) {
+			return null;
+		}
+
+		$image_meta = $metadata['image_meta'];
+		$exif       = array();
+
+		// Map WordPress image_meta to Vernissage EXIF properties.
+		if ( ! empty( $image_meta['created_timestamp'] ) ) {
+			$exif['createDate'] = \gmdate( 'c', (int) $image_meta['created_timestamp'] );
+		}
+
+		if ( ! empty( $image_meta['shutter_speed'] ) ) {
+			$shutter_speed = (float) $image_meta['shutter_speed'];
+			// Format shutter speed as a fraction (e.g., "1/100") for speeds faster than 1 second.
+			if ( $shutter_speed > 0 && $shutter_speed < 1 ) {
+				$exif['exposureTime'] = '1/' . \round( 1 / $shutter_speed );
+			} elseif ( $shutter_speed >= 1 ) {
+				$exif['exposureTime'] = (string) $shutter_speed;
+			}
+		}
+
+		if ( ! empty( $image_meta['aperture'] ) ) {
+			$exif['fNumber'] = 'f/' . (float) $image_meta['aperture'];
+		}
+
+		if ( ! empty( $image_meta['focal_length'] ) ) {
+			$exif['focalLength'] = (string) ( (float) $image_meta['focal_length'] );
+		}
+
+		if ( ! empty( $image_meta['iso'] ) ) {
+			$exif['photographicSensitivity'] = (string) ( (int) $image_meta['iso'] );
+		}
+
+		if ( ! empty( $image_meta['camera'] ) ) {
+			$exif['model'] = \sanitize_text_field( $image_meta['camera'] );
+		}
+
+		/**
+		 * Filter the EXIF data for an image attachment.
+		 *
+		 * @param array $exif          The EXIF data object for the Vernissage namespace.
+		 * @param array $image_meta    The WordPress image_meta array.
+		 * @param int   $attachment_id The attachment ID.
+		 *
+		 * @return array The filtered EXIF data object.
+		 */
+		$exif = \apply_filters( 'activitypub_image_exif', $exif, $image_meta, $attachment_id );
+
+		return ! empty( $exif ) ? $exif : null;
+	}
+
 	/**
 	 * Filter attachments to ensure uniqueness based on their ID.
 	 *

tests/phpunit/tests/includes/transformer/class-test-post.php

@@ -1204,4 +1204,197 @@ public function wordpress_post_format_template_provider() {
 			),
 		);
 	}
+
+	/**
+	 * Test get_exif_data method returns null when no EXIF data.
+	 *
+	 * @covers \Activitypub\Transformer\Base::get_exif_data
+	 */
+	public function test_get_exif_data_returns_null_when_no_exif() {
+		$attachment_id = $this->create_upload_object( AP_TESTS_DIR . '/data/assets/test.jpg' );
+
+		// Clear image_meta to simulate no EXIF data.
+		$metadata               = \wp_get_attachment_metadata( $attachment_id );
+		$metadata['image_meta'] = array();
+		\wp_update_attachment_metadata( $attachment_id, $metadata );
+
+		$post        = self::factory()->post->create_and_get();
+		$transformer = new Post( $post );
+
+		$reflection = new \ReflectionClass( Post::class );
+		$method     = $reflection->getMethod( 'get_exif_data' );
+		if ( \PHP_VERSION_ID < 80100 ) {
+			$method->setAccessible( true );
+		}
+
+		$exif = $method->invoke( $transformer, $attachment_id );
+
+		$this->assertNull( $exif, 'Should return null when no EXIF data is available.' );
+
+		\wp_delete_attachment( $attachment_id, true );
+	}
+
+	/**
+	 * Test get_exif_data method returns EXIF data in Vernissage format.
+	 *
+	 * @covers \Activitypub\Transformer\Base::get_exif_data
+	 */
+	public function test_get_exif_data_returns_vernissage_format() {
+		$attachment_id = $this->create_upload_object( AP_TESTS_DIR . '/data/assets/test.jpg' );
+
+		// Set up mock EXIF data.
+		$metadata               = \wp_get_attachment_metadata( $attachment_id );
+		$metadata['image_meta'] = array(
+			'created_timestamp' => 1704067200, // 2024-01-01 00:00:00 UTC.
+			'shutter_speed'     => 0.01,       // 1/100.
+			'aperture'          => 2.8,
+			'focal_length'      => 50,
+			'iso'               => 400,
+			'camera'            => 'Canon EOS R5',
+		);
+		\wp_update_attachment_metadata( $attachment_id, $metadata );
+
+		$post        = self::factory()->post->create_and_get();
+		$transformer = new Post( $post );
+
+		$reflection = new \ReflectionClass( Post::class );
+		$method     = $reflection->getMethod( 'get_exif_data' );
+		if ( \PHP_VERSION_ID < 80100 ) {
+			$method->setAccessible( true );
+		}
+
+		$exif = $method->invoke( $transformer, $attachment_id );
+
+		$this->assertIsArray( $exif, 'Should return an array.' );
+		$this->assertArrayHasKey( 'createDate', $exif, 'Should contain createDate.' );
+		$this->assertArrayHasKey( 'exposureTime', $exif, 'Should contain exposureTime.' );
+		$this->assertArrayHasKey( 'fNumber', $exif, 'Should contain fNumber.' );
+		$this->assertArrayHasKey( 'focalLength', $exif, 'Should contain focalLength.' );
+		$this->assertArrayHasKey( 'photographicSensitivity', $exif, 'Should contain photographicSensitivity.' );
+		$this->assertArrayHasKey( 'model', $exif, 'Should contain model.' );
+
+		// Check value formats.
+		$this->assertSame( '2024-01-01T00:00:00+00:00', $exif['createDate'], 'createDate should be ISO 8601 format.' );
+		$this->assertSame( '1/100', $exif['exposureTime'], 'exposureTime should be fraction format.' );
+		$this->assertSame( 'f/2.8', $exif['fNumber'], 'fNumber should be f/X.X format.' );
+		$this->assertSame( '50', $exif['focalLength'], 'focalLength should be numeric string.' );
+		$this->assertSame( '400', $exif['photographicSensitivity'], 'photographicSensitivity should be string.' );
+		$this->assertSame( 'Canon EOS R5', $exif['model'], 'model should be camera name.' );
+
+		\wp_delete_attachment( $attachment_id, true );
+	}
+
+	/**
+	 * Test get_exif_data with long exposure (>= 1 second).
+	 *
+	 * @covers \Activitypub\Transformer\Base::get_exif_data
+	 */
+	public function test_get_exif_data_long_exposure() {
+		$attachment_id = $this->create_upload_object( AP_TESTS_DIR . '/data/assets/test.jpg' );
+
+		// Set up mock EXIF data with long exposure.
+		$metadata               = \wp_get_attachment_metadata( $attachment_id );
+		$metadata['image_meta'] = array(
+			'shutter_speed' => 2.5, // 2.5 seconds.
+		);
+		\wp_update_attachment_metadata( $attachment_id, $metadata );
+
+		$post        = self::factory()->post->create_and_get();
+		$transformer = new Post( $post );
+
+		$reflection = new \ReflectionClass( Post::class );
+		$method     = $reflection->getMethod( 'get_exif_data' );
+		if ( \PHP_VERSION_ID < 80100 ) {
+			$method->setAccessible( true );
+		}
+
+		$exif = $method->invoke( $transformer, $attachment_id );
+
+		$this->assertSame( '2.5', $exif['exposureTime'], 'Long exposure should be shown as seconds.' );
+
+		\wp_delete_attachment( $attachment_id, true );
+	}
+
+	/**
+	 * Test that EXIF data is included in image attachments.
+	 *
+	 * @covers \Activitypub\Transformer\Base::transform_attachment
+	 */
+	public function test_transform_attachment_includes_exif() {
+		$attachment_id  = $this->create_upload_object( AP_TESTS_DIR . '/data/assets/test.jpg' );
+		$attachment_src = \wp_get_attachment_image_src( $attachment_id );
+
+		// Set up mock EXIF data.
+		$metadata               = \wp_get_attachment_metadata( $attachment_id );
+		$metadata['image_meta'] = array(
+			'iso'    => 800,
+			'camera' => 'Nikon Z6',
+		);
+		\wp_update_attachment_metadata( $attachment_id, $metadata );
+
+		$post_id = \wp_insert_post(
+			array(
+				'post_author'  => 1,
+				'post_content' => sprintf(
+					'<!-- wp:image {"id": %1$d,"sizeSlug":"large"} --><figure class="wp-block-image"><img src="%2$s" alt="" class="wp-image-%1$d"/></figure><!-- /wp:image -->',
+					$attachment_id,
+					$attachment_src[0]
+				),
+				'post_status'  => 'publish',
+			)
+		);
+
+		$object      = Post::transform( get_post( $post_id ) )->to_object();
+		$attachments = $object->get_attachment();
+
+		$this->assertCount( 1, $attachments, 'Should have one attachment.' );
+		$this->assertArrayHasKey( 'exif', $attachments[0], 'Attachment should include exif object.' );
+		$this->assertArrayHasKey( 'photographicSensitivity', $attachments[0]['exif'], 'EXIF should include ISO.' );
+		$this->assertArrayHasKey( 'model', $attachments[0]['exif'], 'EXIF should include camera model.' );
+		$this->assertSame( '800', $attachments[0]['exif']['photographicSensitivity'], 'ISO should be 800.' );
+		$this->assertSame( 'Nikon Z6', $attachments[0]['exif']['model'], 'Camera model should be Nikon Z6.' );
+
+		\wp_delete_attachment( $attachment_id, true );
+	}
+
+	/**
+	 * Test activitypub_image_exif filter.
+	 *
+	 * @covers \Activitypub\Transformer\Base::get_exif_data
+	 */
+	public function test_get_exif_data_filter() {
+		$attachment_id = $this->create_upload_object( AP_TESTS_DIR . '/data/assets/test.jpg' );
+
+		// Set up mock EXIF data.
+		$metadata               = \wp_get_attachment_metadata( $attachment_id );
+		$metadata['image_meta'] = array(
+			'camera' => 'Test Camera',
+		);
+		\wp_update_attachment_metadata( $attachment_id, $metadata );
+
+		// Add filter to extend EXIF data.
+		$filter = function ( $exif, $image_meta, $id ) use ( $attachment_id ) {
+			$this->assertSame( $attachment_id, $id, 'Filter should receive correct attachment ID.' );
+			$exif['make'] = 'Test Manufacturer';
+			return $exif;
+		};
+		\add_filter( 'activitypub_image_exif', $filter, 10, 3 );
+
+		$post        = self::factory()->post->create_and_get();
+		$transformer = new Post( $post );
+
+		$reflection = new \ReflectionClass( Post::class );
+		$method     = $reflection->getMethod( 'get_exif_data' );
+		if ( \PHP_VERSION_ID < 80100 ) {
+			$method->setAccessible( true );
+		}
+
+		$exif = $method->invoke( $transformer, $attachment_id );
+
+		$this->assertArrayHasKey( 'make', $exif, 'Filter should be able to add EXIF properties.' );
+		$this->assertSame( 'Test Manufacturer', $exif['make'], 'Filter should set make.' );
+
+		\remove_filter( 'activitypub_image_exif', $filter );
+		\wp_delete_attachment( $attachment_id, true );
+	}
 }