blurhash generation

Signed-off-by: Maxence Lange <maxence@artificial-owl.com>

build/psalm-baseline.xml

@@ -2147,6 +2147,20 @@
       <code>$jobList</code>
     </MoreSpecificImplementedParamType>
   </file>
+  <file src="lib/private/Blurhash/Listener/GenerateBlurhashMetadata.php">
+    <InvalidArgument>
+      <code>$image</code>
+      <code>$image</code>
+      <code>$image</code>
+      <code>$image</code>
+    </InvalidArgument>
+    <InvalidReturnStatement>
+      <code>$image</code>
+    </InvalidReturnStatement>
+    <InvalidReturnType>
+      <code>GdImage|false</code>
+    </InvalidReturnType>
+  </file>
   <file src="lib/private/Cache/CappedMemoryCache.php">
     <MissingTemplateParam>
       <code>\ArrayAccess</code>

lib/private/Blurhash/Listener/GenerateBlurhashMetadata.php

@@ -0,0 +1,164 @@
+<?php
+
+declare(strict_types=1);
+/**
+ * @copyright 2024 Maxence Lange <maxence@artificial-owl.com>
+ *
+ * @author Maxence Lange <maxence@artificial-owl.com>
+ *
+ * @license GNU AGPL version 3 or any later version
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as
+ * published by the Free Software Foundation, either version 3 of the
+ * License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ *
+ */
+
+namespace OC\Blurhash\Listener;
+
+use GdImage;
+use kornrunner\Blurhash\Blurhash;
+use OC\Files\Node\File;
+use OCP\EventDispatcher\Event;
+use OCP\EventDispatcher\IEventDispatcher;
+use OCP\EventDispatcher\IEventListener;
+use OCP\Files\GenericFileException;
+use OCP\Files\NotFoundException;
+use OCP\Files\NotPermittedException;
+use OCP\FilesMetadata\AMetadataEvent;
+use OCP\FilesMetadata\Event\MetadataBackgroundEvent;
+use OCP\FilesMetadata\Event\MetadataLiveEvent;
+use OCP\IPreview;
+use OCP\Lock\LockedException;
+
+/**
+ * Generate a Blurhash string as metadata when image file is uploaded/edited.
+ *
+ * @template-implements IEventListener<AMetadataEvent>
+ */
+class GenerateBlurhashMetadata implements IEventListener {
+	private const RESIZE_BOXSIZE = 300;
+
+	private const COMPONENTS_X = 4;
+	private const COMPONENTS_Y = 3;
+
+	public function __construct(
+		private IPreview $preview
+	) {
+	}
+
+	/**
+	 * @throws NotPermittedException
+	 * @throws GenericFileException
+	 * @throws LockedException
+	 */
+	public function handle(Event $event): void {
+		if (!($event instanceof MetadataLiveEvent)
+			&& !($event instanceof MetadataBackgroundEvent)) {
+			return;
+		}
+
+		$file = $event->getNode();
+		if (!($file instanceof File) || !str_starts_with($file->getMimetype(), 'image/')) {
+			return;
+		}
+
+		if ($event instanceof MetadataLiveEvent) {
+			$event->requestBackgroundJob();
+
+			return;
+		}
+
+		try {
+			$preview = $this->preview->getPreview($file, 256, 256);
+			$image = imagecreatefromstring($preview->getContent());
+		} catch (NotFoundException $e) {
+			// https://github.com/nextcloud/server/blob/9d70fd3e64b60a316a03fb2b237891380c310c58/lib/private/legacy/OC_Image.php#L668
+			// The preview system can fail on huge picture, in that case we use our own resize image.
+			$image = $this->resizedImageFromFile($file);
+		}
+
+		if ($image === false) {
+			return;
+		}
+
+		$metadata = $event->getMetadata();
+		$metadata->setString('blurhash', $this->generateBlurHash($image));
+	}
+
+	/**
+	 * @param File $file
+	 *
+	 * @return GdImage|false
+	 * @throws GenericFileException
+	 * @throws NotPermittedException
+	 * @throws LockedException
+	 */
+	private function resizedImageFromFile(File $file): GdImage|false {
+		$image = imagecreatefromstring($file->getContent());
+		if ($image === false) {
+			return false;
+		}
+
+		$currX = imagesx($image);
+		$currY = imagesy($image);
+
+		if ($currX > $currY) {
+			$newX = self::RESIZE_BOXSIZE;
+			$newY = intval($currY * $newX / $currX);
+		} else {
+			$newY = self::RESIZE_BOXSIZE;
+			$newX = intval($currX * $newY / $currY);
+		}
+
+		$newImage = imagescale($image, $newX, $newY);
+		if (false !== $newImage) {
+			$image = $newImage;
+		}
+
+		return $image;
+	}
+
+	/**
+	 * @param GdImage $image
+	 *
+	 * @return string
+	 */
+	public function generateBlurHash(GdImage $image): string {
+		$width = imagesx($image);
+		$height = imagesy($image);
+
+		$pixels = [];
+		for ($y = 0; $y < $height; ++$y) {
+			$row = [];
+			for ($x = 0; $x < $width; ++$x) {
+				$index = imagecolorat($image, $x, $y);
+				$colors = imagecolorsforindex($image, $index);
+				$row[] = [$colors['red'], $colors['green'], $colors['blue']];
+			}
+
+			$pixels[] = $row;
+		}
+
+		return Blurhash::encode($pixels, self::COMPONENTS_X, self::COMPONENTS_Y);
+	}
+
+	/**
+	 * @param IEventDispatcher $eventDispatcher
+	 *
+	 * @return void
+	 */
+	public static function loadListeners(IEventDispatcher $eventDispatcher): void {
+		$eventDispatcher->addServiceListener(MetadataLiveEvent::class, self::class);
+		$eventDispatcher->addServiceListener(MetadataBackgroundEvent::class, self::class);
+	}
+}

lib/private/Server.php

@@ -68,6 +68,7 @@
 use OC\Authentication\LoginCredentials\Store;
 use OC\Authentication\Token\IProvider;
 use OC\Avatar\AvatarManager;
+use OC\Blurhash\Listener\GenerateBlurhashMetadata;
 use OC\Collaboration\Collaborators\GroupPlugin;
 use OC\Collaboration\Collaborators\MailPlugin;
 use OC\Collaboration\Collaborators\RemoteGroupPlugin;
@@ -1482,6 +1483,7 @@ private function connectDispatcher(): void {
 		$eventDispatcher->addServiceListener(BeforeUserDeletedEvent::class, BeforeUserDeletedListener::class);
 
 		FilesMetadataManager::loadListeners($eventDispatcher);
+		GenerateBlurhashMetadata::loadListeners($eventDispatcher);
 	}
 
 	/**