fix(blurhash): Use preview API to generate the previews

This allows to benefit from all the checks done by the preview API.
This also use the newly introduced `cacheResult` argument to limit disk usage.

Signed-off-by: Louis Chemineau <louis@chmn.me>

build/psalm-baseline.xml

@@ -2230,24 +2230,9 @@
     </InvalidReturnStatement>
   </file>
   <file src="lib/private/Preview/Generator.php">
-    <InvalidArgument>
-      <code><![CDATA[$maxPreviewImage]]></code>
-    </InvalidArgument>
     <LessSpecificReturnType>
       <code><![CDATA[null|string]]></code>
     </LessSpecificReturnType>
-    <MismatchingDocblockParamType>
-      <code><![CDATA[ISimpleFile]]></code>
-    </MismatchingDocblockParamType>
-    <UndefinedInterfaceMethod>
-      <code><![CDATA[height]]></code>
-      <code><![CDATA[height]]></code>
-      <code><![CDATA[preciseResizeCopy]]></code>
-      <code><![CDATA[resizeCopy]]></code>
-      <code><![CDATA[valid]]></code>
-      <code><![CDATA[width]]></code>
-      <code><![CDATA[width]]></code>
-    </UndefinedInterfaceMethod>
   </file>
   <file src="lib/private/Preview/ProviderV1Adapter.php">
     <InvalidReturnStatement>

lib/private/Blurhash/Listener/GenerateBlurhashMetadata.php

@@ -19,6 +19,7 @@ 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;
 
 /**
@@ -27,11 +28,14 @@ use OCP\Lock\LockedException;
  * @template-implements IEventListener<AMetadataEvent>
  */
 class GenerateBlurhashMetadata implements IEventListener {
-	private const RESIZE_BOXSIZE = 30;
-
 	private const COMPONENTS_X = 4;
 	private const COMPONENTS_Y = 3;
 
+	public function __construct(
+		private IPreview $preview,
+	) {
+	}
+
 	/**
 	 * @throws NotPermittedException
 	 * @throws GenericFileException
@@ -64,7 +68,9 @@ class GenerateBlurhashMetadata implements IEventListener {
 			return;
 		}
 
-		$image = $this->resizedImageFromFile($file);
+		$preview = $this->preview->getPreview($file, 64, 64, cacheResult: false);
+		$image = @imagecreatefromstring($preview->getContent());
+
 		if (!$image) {
 			return;
 		}
@@ -73,35 +79,6 @@ class GenerateBlurhashMetadata implements IEventListener {
 			->setEtag('blurhash', $currentEtag);
 	}
 
-	/**
-	 * @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, $newY);
-		return ($newImage !== false) ? $newImage : $image;
-	}
-
 	/**
 	 * @param GdImage $image
 	 *

lib/private/Preview/Generator.php

@@ -350,11 +350,10 @@ class Generator {
 
 				$path = $this->generatePath($preview->width(), $preview->height(), $crop, $max, $preview->dataMimeType(), $prefix);
 				try {
-					$file = $previewFolder->newFile($path);
 					if ($preview instanceof IStreamImage) {
-						$file->putContent($preview->resource());
+						return $previewFolder->newFile($path, $preview->resource());
 					} else {
-						$file->putContent($preview->data());
+						return $previewFolder->newFile($path, $preview->data());
 					}
 				} catch (NotPermittedException $e) {
 					throw new NotFoundException();
@@ -540,14 +539,13 @@ class Generator {
 		$path = $this->generatePath($width, $height, $crop, false, $preview->dataMimeType(), $prefix);
 		try {
 			if ($cacheResult) {
-				$file = $previewFolder->newFile($path, $preview->data());
+				return $previewFolder->newFile($path, $preview->data());
 			} else {
 				return new InMemoryFile($path, $preview->data());
 			}
 		} catch (NotPermittedException $e) {
 			throw new NotFoundException();
 		}
-
 		return $file;
 	}
 

tests/lib/Preview/GeneratorTest.php

@@ -22,25 +22,25 @@ use OCP\Preview\IProviderV2;
 use Psr\Log\LoggerInterface;
 
 class GeneratorTest extends \Test\TestCase {
-	/** @var IConfig|\PHPUnit\Framework\MockObject\MockObject */
+	/** @var IConfig&\PHPUnit\Framework\MockObject\MockObject */
 	private $config;
 
-	/** @var IPreview|\PHPUnit\Framework\MockObject\MockObject */
+	/** @var IPreview&\PHPUnit\Framework\MockObject\MockObject */
 	private $previewManager;
 
-	/** @var IAppData|\PHPUnit\Framework\MockObject\MockObject */
+	/** @var IAppData&\PHPUnit\Framework\MockObject\MockObject */
 	private $appData;
 
-	/** @var GeneratorHelper|\PHPUnit\Framework\MockObject\MockObject */
+	/** @var GeneratorHelper&\PHPUnit\Framework\MockObject\MockObject */
 	private $helper;
 
-	/** @var IEventDispatcher|\PHPUnit\Framework\MockObject\MockObject */
+	/** @var IEventDispatcher&\PHPUnit\Framework\MockObject\MockObject */
 	private $eventDispatcher;
 
 	/** @var Generator */
 	private $generator;
 
-	private LoggerInterface|\PHPUnit\Framework\MockObject\MockObject $logger;
+	private LoggerInterface&\PHPUnit\Framework\MockObject\MockObject $logger;
 
 	protected function setUp(): void {
 		parent::setUp();
@@ -196,18 +196,10 @@ class GeneratorTest extends \Test\TestCase {
 		$previewFolder->method('getDirectoryListing')
 			->willReturn([]);
 		$previewFolder->method('newFile')
-			->willReturnCallback(function ($filename) use ($maxPreview, $previewFile) {
-				if ($filename === '2048-2048-max.png') {
-					return $maxPreview;
-				} elseif ($filename === '256-256.png') {
-					return $previewFile;
-				}
-				$this->fail('Unexpected file');
-			});
-
-		$maxPreview->expects($this->once())
-			->method('putContent')
-			->with($this->equalTo('my data'));
+			->willReturnMap([
+				['2048-2048-max.png', 'my data', $maxPreview],
+				['256-256.png', 'my resized data', $previewFile],
+			]);
 
 		$previewFolder->method('getFile')
 			->with($this->equalTo('256-256.png'))
@@ -218,10 +210,6 @@ class GeneratorTest extends \Test\TestCase {
 			->with($this->equalTo($maxPreview))
 			->willReturn($image);
 
-		$previewFile->expects($this->once())
-			->method('putContent')
-			->with('my resized data');
-
 		$this->eventDispatcher->expects($this->once())
 			->method('dispatchTyped')
 			->with(new BeforePreviewFetchedEvent($file, 100, 100, false, IPreview::MODE_FILL, null));