PreviewService refactoring

1 files changed, 351 insertions, 0 deletions

diff --git a/preview/preview.php b/preview/preview.php
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--- /dev/null
+++ b/preview/preview.php
@@ -0,0 +1,351 @@
+<?php
+/**
+ * ownCloud - galleryplus
+ *
+ * This file is licensed under the Affero General Public License version 3 or
+ * later. See the COPYING file.
+ *
+ * @author Olivier Paroz <owncloud@interfasys.ch>
+ *
+ * @copyright Olivier Paroz 2014-2015
+ */
+
+namespace OCA\GalleryPlus\Preview;
+
+use OCP\Files\File;
+
+use OCP\AppFramework\Http;
+
+use OCA\GalleryPlus\Utility\SmarterLogger;
+
+/**
+ * Generates previews
+ *
+ * @todo On OC8.1, replace \OC\Preview with OC::$server->getPreviewManager()
+ *
+ * @package OCA\GalleryPlus\Preview
+ */
+class Preview {
+
+	/**
+	 * @type SmarterLogger
+	 */
+	private $logger;
+	/**
+	 * @type string
+	 */
+	private $owner;
+	/**
+	 * @type \OC\Preview
+	 */
+	private $preview;
+	/**
+	 * @type File
+	 */
+	private $file;
+
+	/**
+	 * Constructor
+	 *
+	 * @param SmarterLogger $logger
+	 */
+	public function __construct(
+		SmarterLogger $logger
+	) {
+		$this->logger = $logger;
+	}
+
+	/**
+	 * Initialises the object
+	 *
+	 * @fixme Private API, but can't use the PreviewManager yet as it's incomplete
+	 *
+	 * @param string $owner
+	 * @param File $file
+	 * @param string $imagePathFromFolder
+	 */
+	public function setupView($owner, $file, $imagePathFromFolder) {
+		$this->owner = $owner;
+		$this->file = $file;
+		$this->preview = new \OC\Preview($owner, 'files', $imagePathFromFolder);
+	}
+
+	/**
+	 * Decides if we should download the file instead of generating a preview
+	 *
+	 * @param bool $animatedPreview
+	 * @param bool $download
+	 *
+	 * @return bool
+	 */
+	public function previewRequired($animatedPreview, $download) {
+		$svgPreviewRequired = $this->isSvgPreviewRequired($this->preview);
+		$gifPreviewRequired = $this->isGifPreviewRequired($animatedPreview);
+
+		return $svgPreviewRequired && $gifPreviewRequired && !$download;
+	}
+
+	/**
+	 * Decides if we should download the SVG or generate a preview
+	 *
+	 * @param \OC\Preview $preview
+	 *
+	 * @return bool
+	 */
+	private function isSvgPreviewRequired($preview) {
+		$mime = $this->file->getMimeType();
+
+		/**
+		 * SVGs are downloaded if the SVG converter is disabled
+		 * Files of any media type are downloaded if requested by the client
+		 */
+		if ($mime === 'image/svg+xml' && !$preview->isMimeSupported($mime)) {
+			return false;
+		}
+
+		return true;
+	}
+
+	/**
+	 * Decides if we should download the GIF or generate a preview
+	 *
+	 * @param bool $animatedPreview
+	 *
+	 * @return bool
+	 */
+	private function isGifPreviewRequired($animatedPreview) {
+		$mime = $this->file->getMimeType();
+		$animatedGif = $this->isGifAnimated($this->file);
+
+		/**
+		 * GIFs are downloaded if they're animated and we want to show
+		 * animations
+		 */
+		if ($mime === 'image/gif' && $animatedPreview && $animatedGif) {
+			return false;
+		}
+
+		return true;
+	}
+
+	/**
+	 * Tests if a GIF is animated
+	 *
+	 * An animated gif contains multiple "frames", with each frame having a
+	 * header made up of:
+	 *    * a static 4-byte sequence (\x00\x21\xF9\x04)
+	 *    * 4 variable bytes
+	 *    * a static 2-byte sequence (\x00\x2C) (Photoshop uses \x00\x21)
+	 *
+	 * We read through the file until we reach the end of the file, or we've
+	 * found at least 2 frame headers
+	 *
+	 * @link http://php.net/manual/en/function.imagecreatefromgif.php#104473
+	 *
+	 * @param File $file
+	 *
+	 * @return bool
+	 */
+	private function isGifAnimated($file) {
+		$fileHandle = $file->fopen('rb');
+		$count = 0;
+		while (!feof($fileHandle) && $count < 2) {
+			$chunk = fread($fileHandle, 1024 * 100); //read 100kb at a time
+			$count += preg_match_all(
+				'#\x00\x21\xF9\x04.{4}\x00(\x2C|\x21)#s', $chunk, $matches
+			);
+		}
+
+		fclose($fileHandle);
+
+		return $count > 1;
+	}
+
+	/**
+	 * Returns a preview based on OC's preview class and our custom methods
+	 *
+	 * We don't throw an exception when the preview generator fails,
+	 * instead, until the Preview class is fixed, we send the mime
+	 * icon along with a 415 error code.
+	 *
+	 * @fixme setKeepAspect is missing from public interface.
+	 *     https://github.com/owncloud/core/issues/12772
+	 *
+	 * @param int $maxX
+	 * @param int $maxY
+	 * @param bool $keepAspect
+	 *
+	 * @return array
+	 */
+	public function preparePreview($maxX, $maxY, $keepAspect) {
+		$this->preview->setMaxX($maxX);
+		$this->preview->setMaxY($maxY);
+		$this->preview->setScalingUp(false); // TODO: Need to read from settings
+		$this->preview->setKeepAspect($keepAspect);
+		$this->logger->debug("[PreviewService] Generating a new preview");
+		/** @type \OC_Image $previewData */
+		$previewData = $this->preview->getPreview();
+
+		if ($previewData->valid()) {
+			$perfectPreview = $this->previewValidator($maxX, $maxY);
+		} else {
+			$this->logger->debug("[PreviewService] ERROR! Did not get a preview");
+			$perfectPreview = array(
+				'preview' => $this->getMimeIcon(),
+				'status'  => Http::STATUS_UNSUPPORTED_MEDIA_TYPE
+			);
+		}
+		$perfectPreview['mimetype'] = 'image/png'; // Previews are always sent as PNG
+
+		return $perfectPreview;
+	}
+
+	/**
+	 * Makes sure we return previews of the asked dimensions and fix the cache
+	 * if necessary
+	 *
+	 * The Preview class of OC7 sometimes return previews which are either
+	 * wider or smaller than the asked dimensions. This happens when one of the
+	 * original dimension is smaller than what is asked for
+	 *
+	 * @param int $maxX
+	 * @param int $maxY
+	 *
+	 * @return array<resource,int>
+	 */
+	private function previewValidator($maxX, $maxY) {
+		$previewData = $this->preview->getPreview();
+		$previewX = $previewData->width();
+		$previewY = $previewData->height();
+		$minWidth = 200; // Only fixing the square thumbnails
+
+		if (($previewX > $maxX
+			 || ($previewX < $maxX || $previewY < $maxY)
+				&& $maxX === $minWidth)
+		) {
+			$fixedPreview = $this->fixPreview($previewData, $maxX, $maxY);
+			$previewData = $this->fixPreviewCache($fixedPreview);
+		}
+
+		return array(
+			'preview' => $previewData,
+			'status'  => Http::STATUS_OK
+		);
+	}
+
+	/**
+	 * Makes a preview fit in the asked dimension and fills the empty space
+	 *
+	 * @param \OC_Image $previewData
+	 * @param int $maxX
+	 * @param int $maxY
+	 *
+	 * @return resource
+	 */
+	private function fixPreview($previewData, $maxX, $maxY) {
+		$previewWidth = $previewData->width();
+		$previewHeight = $previewData->height();
+		$fixedPreview = imagecreatetruecolor($maxX, $maxY); // Creates the canvas
+
+		// We make the background transparent
+		imagealphablending($fixedPreview, false);
+		$transparency = imagecolorallocatealpha($fixedPreview, 0, 0, 0, 127);
+		imagefill($fixedPreview, 0, 0, $transparency);
+		imagesavealpha($fixedPreview, true);
+
+		$newDimensions = $this->calculateNewDimensions($previewWidth, $previewHeight, $maxX, $maxY);
+
+		imagecopyresampled(
+			$fixedPreview, $previewData->resource(), $newDimensions['newX'], $newDimensions['newY'],
+			0, 0, $newDimensions['newWidth'], $newDimensions['newHeight'],
+			$previewWidth, $previewHeight
+		);
+
+		return $fixedPreview;
+	}
+
+	/**
+	 * Calculates the new dimensions so that it fits in the dimensions requested by the client
+	 *
+	 * @link https://stackoverflow.com/questions/3050952/resize-an-image-and-fill-gaps-of-proportions-with-a-color
+	 *
+	 * @param int $previewWidth
+	 * @param int $previewHeight
+	 * @param int $maxX
+	 * @param int $maxY
+	 *
+	 * @return array
+	 */
+	private function calculateNewDimensions($previewWidth, $previewHeight, $maxX, $maxY) {
+		if (($previewWidth / $previewHeight) >= ($maxX / $maxY)) {
+			$newWidth = $maxX;
+			$newHeight = $previewHeight * ($maxX / $previewWidth);
+			$newX = 0;
+			$newY = round(abs($maxY - $newHeight) / 2);
+		} else {
+			$newWidth = $previewWidth * ($maxY / $previewHeight);
+			$newHeight = $maxY;
+			$newX = round(abs($maxX - $newWidth) / 2);
+			$newY = 0;
+		}
+
+		return array(
+			'newX'      => $newX,
+			'newY'      => $newY,
+			'newWidth'  => $newWidth,
+			'newHeight' => $newHeight,
+		);
+	}
+
+	/**
+	 * Fixes the preview cache by replacing the broken thumbnail with ours
+	 *
+	 * @param resource $fixedPreview
+	 *
+	 * @return mixed
+	 */
+	private function fixPreviewCache($fixedPreview) {
+		$owner = $this->owner;
+		$file = $this->file;
+		$preview = $this->preview;
+		$fixedPreviewObject = new \OC_Image($fixedPreview); // FIXME: Private API
+		$previewData = $preview->getPreview();
+
+		// Get the location where the broken thumbnail is stored
+		// FIXME: Private API
+		$thumbnailFolder = \OC::$SERVERROOT . '/data/' . $owner . '/';
+		$thumbnail = $thumbnailFolder . $preview->isCached($file->getId());
+
+		// Caching it for next time
+		if ($fixedPreviewObject->save($thumbnail)) {
+			$previewData = $fixedPreviewObject->data();
+		}
+
+		return $previewData;
+	}
+
+	/**
+	 * Returns the media type icon when the server fails to generate a preview
+	 *
+	 * It's not more efficient for the browser to download the mime icon
+	 * directly and won't be necessary once the Preview class sends the mime
+	 * icon when it can't generate a proper preview
+	 * https://github.com/owncloud/core/pull/12546
+	 *
+	 * @return \OC_Image
+	 */
+	private function getMimeIcon() {
+		$mime = $this->file->getMimeType();
+		$iconData = new \OC_Image(); // FIXME: Private API
+
+		// FIXME: private API
+		$image = \OC::$SERVERROOT . mimetype_icon($mime);
+		// OC8 version
+		//$image = $this->serverRoot() . \OCP\Template::mimetype_icon($mime);
+
+		$iconData->loadFromFile($image);
+
+		return $iconData;
+	}
+
+}
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