Modernize previews

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 */
@@ -373,6 +378,9 @@ public function data(): ?string {
 		if (!$this->valid()) {
 			return null;
 		}
+
+		$quality = $this->getQuality();
+
 		ob_start();
 		switch ($this->mimeType) {
 			case "image/png":
@@ -381,12 +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']);
@@ -398,6 +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.
 	 */
@@ -407,6 +444,8 @@ public function __toString() {
 
 	/**
 	 * @return int
+	 * 
+	 * @deprecated
 	 */
 	protected function getJpegQuality(): int {
 		$quality = $this->config->getAppValue('preview', 'jpeg_quality', (string) self::DEFAULT_JPEG_QUALITY);