HEIC previews as JPG rather than PNGs to save space.

lib/private/Preview/HEIC.php

@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 /**
  * @author Thomas Müller <[email protected]>
  *
@@ -22,19 +23,118 @@
 
 namespace OC\Preview;
 
-class HEIC extends Bitmap {
+use OCP\ILogger;
+
+/**
+ * Creates a JPG preview using ImageMagick via the PECL extension
+ *
+ * @package OC\Preview
+ */
+class HEIC extends Provider {
 	/**
 	 * {@inheritDoc}
 	 */
-	public function getMimeType() {
+	public function getMimeType(): string {
 		return '/image\/hei(f|c)/';
 	}
 
 	/**
 	 * {@inheritDoc}
 	 */
-	public function isAvailable(\OCP\Files\FileInfo $file) {
-		return in_array("HEIC", \Imagick::queryFonts("HEI*") );
+	public function isAvailable(\OCP\Files\FileInfo $file): bool {
+		return in_array('HEIC', \Imagick::queryFormats("HEI*"));
+	}
+
+	/**
+	 * {@inheritDoc}
+	 */
+	public function getThumbnail($path, $maxX, $maxY, $scalingup, $fileview) {
+		$tmpPath = $fileview->toTmpFile($path);
+		if (!$tmpPath) {
+			return false;
+		}
+
+		// Creates \Imagick object from the heic file
+		try {
+			$bp = $this->getResizedPreview($tmpPath, $maxX, $maxY);
+			$bp->setFormat('jpg');
+		} catch (\Exception $e) {
+			\OC::$server->getLogger()->logException($e, [
+				'message' => 'File: ' . $fileview->getAbsolutePath($path) . ' Imagick says:',
+				'level' => ILogger::ERROR,
+				'app' => 'core',
+			]);
+			return false;
+		}
+
+		unlink($tmpPath);
+
+		//new bitmap image object
+		$image = new \OC_Image();
+		$image->loadFromData($bp);
+		//check if image object is valid
+		return $image->valid() ? $image : false;
+	}
+
+	/**
+	 * Returns a preview of maxX times maxY dimensions in JPG format
+	 *
+	 *    * The default resolution is already 72dpi, no need to change it for a bitmap output
+	 *    * It's possible to have proper colour conversion using profileimage().
+	 *    ICC profiles are here: http://www.color.org/srgbprofiles.xalter
+	 *    * It's possible to Gamma-correct an image via gammaImage()
+	 *
+	 * @param string $tmpPath the location of the file to convert
+	 * @param int $maxX
+	 * @param int $maxY
+	 *
+	 * @return \Imagick
+	 */
+	private function getResizedPreview($tmpPath, $maxX, $maxY) {
+		$bp = new \Imagick();
+
+		// Layer 0 contains either the bitmap or a flat representation of all vector layers
+		$bp->readImage($tmpPath . '[0]');
+
+		$bp->setImageFormat('jpg');
+
+		$bp = $this->resize($bp, $maxX, $maxY);
+
+		return $bp;
+	}
+
+	/**
+	 * Returns a resized \Imagick object
+	 *
+	 * If you want to know more on the various methods available to resize an
+	 * image, check out this link : @link https://stackoverflow.com/questions/8517304/what-the-difference-of-sample-resample-scale-resize-adaptive-resize-thumbnail-im
+	 *
+	 * @param \Imagick $bp
+	 * @param int $maxX
+	 * @param int $maxY
+	 *
+	 * @return \Imagick
+	 */
+	private function resize($bp, $maxX, $maxY) {
+		list($previewWidth, $previewHeight) = array_values($bp->getImageGeometry());
+
+		// We only need to resize a preview which doesn't fit in the maximum dimensions
+		if ($previewWidth > $maxX || $previewHeight > $maxY) {
+			// If we want a small image (thumbnail) let's be most space- and time-efficient
+			if ($maxX <= 500 && $maxY <= 500) {
+				$bp->thumbnailImage($maxY, $maxX, true);
+				$bp->stripImage();
+			} else {
+				// A bigger image calls for some better resizing algorithm
+				// According to http://www.imagemagick.org/Usage/filter/#lanczos
+				// the catrom filter is almost identical to Lanczos2, but according
+				// to http://php.net/manual/en/imagick.resizeimage.php it is
+				// significantly faster
+				$bp->resizeImage($maxX, $maxY, \Imagick::FILTER_CATROM, 1, true);
+			}
+		}
+
+		return $bp;
 	}
 
 }