Modernize previews

lib/private/Preview/Generator.php

@@ -51,6 +51,8 @@ class Generator {
 	public const SEMAPHORE_ID_ALL = 0x0a11;
 	public const SEMAPHORE_ID_NEW = 0x07ea;
 
+	private \OCP\ILogger $logger;
+
 	/** @var IPreview */
 	private $previewManager;
 	/** @var IConfig */
@@ -64,6 +66,14 @@ class Generator {
 	/** @var IEventDispatcher */
 	private $eventDispatcher;
 
+	/**
+	 * GD image type for the preview format setting
+	 * 
+	 * `null` if the preview format setting is not set (=> use default handling
+	 * instead).
+	 */
+	private null|int $previewImageType;
+
 	public function __construct(
 		IConfig $config,
 		IPreview $previewManager,
@@ -72,12 +82,49 @@ public function __construct(
 		EventDispatcherInterface $legacyEventDispatcher,
 		IEventDispatcher $eventDispatcher
 	) {
+		$this->logger = \OC::$server->getLogger();
+
 		$this->config = $config;
 		$this->previewManager = $previewManager;
 		$this->appData = $appData;
 		$this->helper = $helper;
 		$this->legacyEventDispatcher = $legacyEventDispatcher;
 		$this->eventDispatcher = $eventDispatcher;
+
+		$this->setPreviewImageType();
+	}
+
+	private function setPreviewImageType(): void {
+		// Only allow previews to be common image formats that there is a clear
+		// need for.
+		// See https://developer.mozilla.org/en-US/docs/Web/HTTP/Basics_of_HTTP/MIME_types#image_types
+		$ALLOWED_FORMATS = ['AVIF', 'GIF', 'JPEG', 'PNG', 'WEBP'];
+		$FALLBACK_MESSAGE = 'Falling back to the default preview format.';
+
+		$this->previewImageType = null;
+
+		$previewFormat = strtoupper(
+			$this->config->getAppValue('preview', 'format')
+		);
+
+		if (!$previewFormat) return;
+		if (!in_array($previewFormat, $ALLOWED_FORMATS)) {
+			$this->logger->error(
+				'Preview format must be one of [' .
+				implode(', ', $ALLOWED_FORMATS) .
+				"]; got $previewFormat. $FALLBACK_MESSAGE"
+			);
+			return;
+		}
+		if (!(imagetypes() & constant("IMG_$previewFormat"))) {
+			$this->logger->error(
+				'The installation does not support preview format ' .
+				"$previewFormat. $FALLBACK_MESSAGE"
+			);
+			return;
+		}
+
+		$this->previewImageType = constant("IMAGETYPE_$previewFormat");
 	}
 
 	/**
@@ -132,8 +179,14 @@ public function generatePreviews(File $file, array $specifications, $mimeType =
 			throw new NotFoundException('Cannot read file');
 		}
 
-		if ($mimeType === null) {
-			$mimeType = $file->getMimeType();
+		// `$mimeType` argument overrides preview format setting overrides
+		// default to the same MIME type as the file it is a preview for
+		if (!$mimeType) {
+			if (!is_null($this->previewImageType)) {
+				$mimeType = image_type_to_mime_type($this->previewImageType);
+			} else {
+				$mimeType = $file->getMimeType();
+			}
 		}
 
 		$previewFolder = $this->getPreviewFolder($file);
@@ -271,7 +324,7 @@ private function getSmallImagePreview(ISimpleFolder $previewFolder, File $file,
 					continue;
 				}
 
-				$preview = $this->helper->getThumbnail($provider, $file, 256, 256, $crop);
+				$preview = $this->helper->getThumbnail($provider, $file, 256, 256, $crop, $mimeType);
 
 				if (!($preview instanceof IImage)) {
 					continue;
@@ -437,7 +490,17 @@ private function getMaxPreview(ISimpleFolder $previewFolder, File $file, $mimeTy
 				$previewConcurrency = $this->getNumConcurrentPreviews('preview_concurrency_new');
 				$sem = self::guardWithSemaphore(self::SEMAPHORE_ID_NEW, $previewConcurrency);
 				try {
-					$preview = $this->helper->getThumbnail($provider, $file, $maxWidth, $maxHeight);
+					// Although we know the provider here, and it *should* know
+					// its own MIME type, note that it actually doesn't - so we
+					// have to pass it.
+					// 
+					// *`IProviderV2->getMimeType`*
+					// 
+					// > Regex with the mimetypes that are supported by this
+					// provider
+					// 
+					// This is also the case for `$this->getSmallImagePreview`.
+					$preview = $this->helper->getThumbnail($provider, $file, $maxWidth, $maxHeight, false, $mimeType);
 				} finally {
 					self::unguardWithSemaphore($sem);
 				}
@@ -692,6 +755,9 @@ private function getPreviewFolder(File $file) {
 	 * @param string $mimeType
 	 * @return null|string
 	 * @throws \InvalidArgumentException
+	 * 
+	 * @deprecated this is goofy
+	 * @see https://www.php.net/manual/en/function.image-type-to-extension.php
 	 */
 	private function getExtention($mimeType) {
 		switch ($mimeType) {
@@ -701,6 +767,8 @@ private function getExtention($mimeType) {
 				return 'jpg';
 			case 'image/gif':
 				return 'gif';
+			case 'image/webp':
+				return 'webp';
 			default:
 				throw new \InvalidArgumentException('Not a valid mimetype: "' . $mimeType . '"');
 		}

lib/private/Preview/GeneratorHelper.php

@@ -57,11 +57,11 @@ public function __construct(IRootFolder $rootFolder, IConfig $config) {
 	 *
 	 * @return bool|IImage
 	 */
-	public function getThumbnail(IProviderV2 $provider, File $file, $maxWidth, $maxHeight, bool $crop = false) {
+	public function getThumbnail(IProviderV2 $provider, File $file, $maxWidth, $maxHeight, bool $crop = false, string $mimeType = null) {
 		if ($provider instanceof Imaginary) {
 			return $provider->getCroppedThumbnail($file, $maxWidth, $maxHeight, $crop) ?? false;
 		}
-		return $provider->getThumbnail($file, $maxWidth, $maxHeight) ?? false;
+		return $provider->getThumbnail($file, $maxWidth, $maxHeight, $mimeType) ?? false;
 	}
 
 	/**

lib/private/Preview/Image.php

@@ -36,7 +36,7 @@ abstract class Image extends ProviderV2 {
 	/**
 	 * {@inheritDoc}
 	 */
-	public function getThumbnail(File $file, int $maxX, int $maxY): ?IImage {
+	public function getThumbnail(File $file, int $maxX, int $maxY, string $mimeType = null): ?IImage {
 		$maxSizeForImages = \OC::$server->getConfig()->getSystemValueInt('preview_max_filesize_image', 50);
 		$size = $file->getSize();
 
@@ -55,6 +55,7 @@ public function getThumbnail(File $file, int $maxX, int $maxY): ?IImage {
 
 		if ($image->valid()) {
 			$image->scaleDownToFit($maxX, $maxY);
+			if ($mimeType) $image->setMimeType($mimeType);
 
 			return $image;
 		}

lib/private/PreviewManager.php

@@ -243,13 +243,15 @@ public function isMimeSupported($mimeType = '*') {
 	/**
 	 * Check if a preview can be generated for a file
 	 */
-	public function isAvailable(\OCP\Files\FileInfo $file): bool {
+	public function isAvailable(\OCP\Files\FileInfo $file, ?string $previewMimeType = null): bool {
+		if (!$previewMimeType) $previewMimeType = $file->getMimeType();
+
 		if (!$this->config->getSystemValue('enable_previews', true)) {
 			return false;
 		}
 
 		$this->registerCoreProviders();
-		if (!$this->isMimeSupported($file->getMimetype())) {
+		if (!$this->isMimeSupported($previewMimeType)) {
 			return false;
 		}
 
@@ -259,7 +261,7 @@ public function isAvailable(\OCP\Files\FileInfo $file): bool {
 		}
 
 		foreach ($this->providers as $supportedMimeType => $providers) {
-			if (preg_match($supportedMimeType, $file->getMimetype())) {
+			if (preg_match($supportedMimeType, $previewMimeType)) {
 				foreach ($providers as $providerClosure) {
 					$provider = $this->helper->getProvider($providerClosure);
 					if (!($provider instanceof IProviderV2)) {

lib/private/legacy/OC_Image.php

@@ -52,7 +52,12 @@ class OC_Image implements \OCP\IImage {
 	// Default memory limit for images to load (256 MBytes).
 	protected const DEFAULT_MEMORY_LIMIT = 256;
 
-	// Default quality for jpeg images
+	/**
+	 * Default quality for jpeg images
+	 * 
+	 * @deprecated this choice should be left to the image library
+	 * @see https://www.php.net/manual/en/function.imagejpeg.php#refsect1-function.imagejpeg-parameters
+	 */
 	protected const DEFAULT_JPEG_QUALITY = 80;
 
 	/** @var false|resource|\GdImage */
@@ -123,6 +128,19 @@ public function mimeType(): ?string {
 		return $this->valid() ? $this->mimeType : null;
 	}
 
+	public function setMimeType(string $mimeType): void {
+		$this->mimeType = $mimeType;
+	}
+
+	/**
+	 * Goofy alias for `mimeType`
+	 * 
+	 * @deprecated in favor of `mimeType`
+	 */
+	public function dataMimeType(): ?string {
+		return $this->mimeType();
+	}
+
 	/**
 	 * Returns the width of the image or -1 if no image is loaded.
 	 *
@@ -352,23 +370,6 @@ public function resource() {
 		return $this->resource;
 	}
 
-	/**
-	 * @return string Returns the mimetype of the data. Returns null if the data is not valid.
-	 */
-	public function dataMimeType(): ?string {
-		if (!$this->valid()) {
-			return null;
-		}
-
-		switch ($this->mimeType) {
-			case 'image/png':
-			case 'image/jpeg':
-			case 'image/gif':
-				return $this->mimeType;
-			default:
-				return 'image/png';
-		}
-	}
 
 	/**
 	 * @return null|string Returns the raw image data.
@@ -377,6 +378,9 @@ public function data(): ?string {
 		if (!$this->valid()) {
 			return null;
 		}
+
+		$quality = $this->getQuality();
+
 		ob_start();
 		switch ($this->mimeType) {
 			case "image/png":
@@ -385,12 +389,14 @@ public function data(): ?string {
 			case "image/jpeg":
 				/** @psalm-suppress InvalidScalarArgument */
 				imageinterlace($this->resource, (PHP_VERSION_ID >= 80000 ? true : 1));
-				$quality = $this->getJpegQuality();
-				$res = imagejpeg($this->resource, null, $quality);
+				$res = imagejpeg($this->resource, null, $this->getJpegQuality());
 				break;
 			case "image/gif":
 				$res = imagegif($this->resource);
 				break;
+			case "image/webp":
+				$res = imagewebp($this->resource, null, $quality);
+				break;
 			default:
 				$res = imagepng($this->resource);
 				$this->logger->info('OC_Image->data. Could not guess mime-type, defaulting to png', ['app' => 'core']);
@@ -402,6 +408,33 @@ public function data(): ?string {
 		return ob_get_clean();
 	}
 
+	/**
+	 * Gets the image quality with which to write lossy image previews
+	 * 
+	 * @return int the image quality on a scale of 0-100, or -1 for the default
+	 */
+	private function getQuality(): int {
+		$quality = $this->config->getAppValue('preview', 'quality');
+
+		if ($quality && (!intval($quality) || $quality < 0 || $quality > 100)) {
+			$this->logger->error(
+				'Preview quality must be an integer from 0 to 100; got ' .
+				"$quality. Falling back to the default preview quality."
+			);
+		}
+
+		// If quality is not set by the user or is invalid, then set it to the
+		// GD default value to entrust choosing a well-optimized default
+		// quality to the image library (which should make a much more educated
+		// choice than we would make). Hopefully GD doesn't mangle this idea...
+		// but it appears they do - WebP default should be 75 yet is 80.
+		// 
+		// See https://developers.google.com/speed/webp/docs/cwebp#options
+		if (!$quality) $quality = -1;
+
+		return (int) $quality;
+	}
+
 	/**
 	 * @return string - base64 encoded, which is suitable for embedding in a VCard.
 	 */
@@ -411,6 +444,8 @@ public function __toString() {
 
 	/**
 	 * @return int
+	 * 
+	 * @deprecated
 	 */
 	protected function getJpegQuality(): int {
 		$quality = $this->config->getAppValue('preview', 'jpeg_quality', (string) self::DEFAULT_JPEG_QUALITY);

lib/public/IPreview.php

@@ -108,10 +108,11 @@ public function isMimeSupported($mimeType = '*');
 	 * Check if a preview can be generated for a file
 	 *
 	 * @param \OCP\Files\FileInfo $file
+	 * @param ?string $previewMimeType MIME type of the preview to be generated
 	 * @return bool
 	 * @since 8.0.0
 	 */
-	public function isAvailable(\OCP\Files\FileInfo $file);
+	public function isAvailable(\OCP\Files\FileInfo $file, string $previewMimeType);
 
 	/**
 	 * Generates previews of a file