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<?php
/**
* Nextcloud - Gallery
*
* This file is licensed under the Affero General Public License version 3 or
* later. See the COPYING file.
*
* @author Olivier Paroz <galleryapps@oparoz.com>
*
* @copyright Olivier Paroz 2017
*/
namespace OCA\Gallery\Service;
use OCP\Files\File;
use OCP\Image;
use OCP\IPreview;
use OCP\ILogger;
use OCA\Gallery\Environment\Environment;
/**
* Generates previews
*
* @package OCA\Gallery\Service
*/
class PreviewService extends Service {
use Base64Encode;
/** @var IPreview */
private $previewManager;
/**
* Constructor
*
* @param string $appName
* @param Environment $environment
* @param IPreview $previewManager
* @param ILogger $logger
*/
public function __construct(
$appName,
Environment $environment,
IPreview $previewManager,
ILogger $logger
) {
parent::__construct($appName, $environment, $logger);
$this->previewManager = $previewManager;
}
/**
* Decides if we should download the file instead of generating a preview
*
* @param File $file
* @param bool $animatedPreview
*
* @return bool
*/
public function isPreviewRequired($file, $animatedPreview) {
$mime = $file->getMimeType();
if ($mime === 'image/svg+xml') {
return $this->isSvgPreviewRequired();
}
if ($mime === 'image/gif') {
return $this->isGifPreviewRequired($file, $animatedPreview);
}
return true;
}
/**
* Returns an array containing everything needed by the client to be able to display a preview
*
* * fileid: the file's ID
* * mimetype: the file's media type
* * preview: the preview's content
*
* Example logger
* $this->logger->debug(
* "[PreviewService] Path : {path} / mime: {mimetype} / fileid: {fileid}",
* [
* 'path' => $preview['data']['path'],
* 'mimetype' => $preview['data']['mimetype'],
* 'fileid' => $preview['fileid']
* ]
* );
*
* @todo Get the max size from the settings
*
* @param File $file
* @param int $maxX asked width for the preview
* @param int $maxY asked height for the preview
* @param bool $keepAspect
* @param bool $base64Encode
*
* @return string|\OC_Image|string|false preview data
* @throws InternalServerErrorServiceException
*/
public function createPreview(
$file, $maxX = 0, $maxY = 0, $keepAspect = true, $base64Encode = false
) {
try {
$preview = $this->previewManager->getPreview($file, $maxX, $maxY, !$keepAspect);
$img = new Image($preview->getContent());
$mimeType = $img->mimeType();
if ($img && $base64Encode) {
$img = $this->encode($img);
}
return [
'preview' => $img,
'mimetype' => $mimeType
];
} catch (\Exception $exception) {
throw new InternalServerErrorServiceException('Preview generation has failed');
}
}
/**
* Returns true if the passed mime type is supported
*
* In case of a failure, we just return that the media type is not supported
*
* @param string $mimeType
*
* @return boolean
*/
private function isMimeSupported($mimeType = '*') {
try {
return $this->previewManager->isMimeSupported($mimeType);
} catch (\Exception $exception) {
unset($exception);
return false;
}
}
/**
* Decides if we should download the SVG or generate a preview
*
* SVGs are downloaded if the SVG converter is disabled
* Files of any media type are downloaded if requested by the client
*
* @return bool
*/
private function isSvgPreviewRequired() {
return $this->isMimeSupported('image/svg+xml');
}
/**
* Decides if we should download the GIF or generate a preview
*
* GIFs are downloaded if they're animated and we want to show
* animations
*
* @param File $file
* @param bool $animatedPreview
*
* @return bool
*/
private function isGifPreviewRequired($file, $animatedPreview) {
$gifSupport = $this->isMimeSupported('image/gif');
$animatedGif = $this->isGifAnimated($file);
return $gifSupport && !($animatedGif && $animatedPreview);
}
/**
* 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) {
$count = 0;
$fileHandle = $this->isFileReadable($file);
if ($fileHandle) {
while (!feof($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;
}
/**
* Determines if we can read the content of the file and returns a file pointer resource
*
* We can't use something like $node->isReadable() as it's too unreliable
* Some storage classes just check for the presence of the file
*
* @param File $file
*
* @return resource
* @throws InternalServerErrorServiceException
*/
private function isFileReadable($file) {
try {
$fileHandle = $file->fopen('rb');
if (!$fileHandle) {
throw new \Exception();
}
} catch (\Exception $exception) {
throw new InternalServerErrorServiceException(
'Something went wrong when trying to read' . $file->getPath()
);
}
return $fileHandle;
}
}