diff --git a/lib/private/preview.php b/lib/private/preview.php
index 26016555a3..0187b4aacb 100755
--- a/lib/private/preview.php
+++ b/lib/private/preview.php
@@ -13,6 +13,8 @@
  */
 namespace OC;
 
+use OC\Preview\Provider;
+
 require_once 'preview/image.php';
 require_once 'preview/movies.php';
 require_once 'preview/mp3.php';
@@ -39,15 +41,16 @@ class Preview {
 	private $file;
 	private $maxX;
 	private $maxY;
-	private $scalingup;
-	private $mimetype;
+	private $scalingUp;
+	private $mimeType;
 
 	//filemapper used for deleting previews
 	// index is path, value is fileinfo
 	static public $deleteFileMapper = array();
 
-	//preview images object
 	/**
+	 * preview images object
+	 *
 	 * @var \OC_Image
 	 */
 	private $preview;
@@ -109,7 +112,7 @@ class Preview {
 	 * @brief returns the path of the file you want a thumbnail from
 	 * @return string
 	 */
-	public function    getFile() {
+	public function getFile() {
 		return $this->file;
 	}
 
@@ -134,7 +137,7 @@ class Preview {
 	 * @return bool
 	 */
 	public function getScalingUp() {
-		return $this->scalingup;
+		return $this->scalingUp;
 	}
 
 	/**
@@ -191,18 +194,18 @@ class Preview {
 		if ($file !== '') {
 			$this->getFileInfo();
 			if($this->info !== null && $this->info !== false) {
-				$this->mimetype = $this->info->getMimetype();
+				$this->mimeType = $this->info->getMimetype();
 			}
 		}
 		return $this;
 	}
 
 	/**
-	 * @brief set mimetype explicitely
-	 * @param string $mimetype
+	 * @brief set mime type explicitly
+	 * @param string $mimeType
 	 */
-	public function setMimetype($mimetype) {
-		$this->mimetype = $mimetype;
+	public function setMimetype($mimeType) {
+		$this->mimeType = $mimeType;
 	}
 
 	/**
@@ -254,7 +257,7 @@ class Preview {
 		if ($this->getMaxScaleFactor() === 1) {
 			$scalingUp = false;
 		}
-		$this->scalingup = $scalingUp;
+		$this->scalingUp = $scalingUp;
 		return $this;
 	}
 
@@ -314,81 +317,42 @@ class Preview {
 
 	/**
 	 * @brief check if thumbnail or bigger version of thumbnail of file is cached
-	 * @return mixed (bool / string)
-	 *                false if thumbnail does not exist
-	 *                path to thumbnail if thumbnail exists
+	 * @param int $fileId fileId of the original image
+	 * @return string|false path to thumbnail if it exists or false
 	 */
-	private function isCached() {
-		$file = $this->getFile();
-		$maxX = $this->getMaxX();
-		$maxY = $this->getMaxY();
-		$scalingUp = $this->getScalingUp();
-		$maxScaleFactor = $this->getMaxScaleFactor();
-
-		$fileInfo = $this->getFileInfo($file);
-		$fileId = $fileInfo->getId();
-
+	public function isCached($fileId) {
 		if (is_null($fileId)) {
 			return false;
 		}
+		
+		$maxX = $this->getMaxX();
+		$maxY = $this->getMaxY();
 
 		$previewPath = $this->getThumbnailsFolder() . '/' . $fileId . '/';
-		if (!$this->userView->is_dir($previewPath)) {
-			return false;
-		}
 
 		//does a preview with the wanted height and width already exist?
 		if ($this->userView->file_exists($previewPath . $maxX . '-' . $maxY . '.png')) {
 			return $previewPath . $maxX . '-' . $maxY . '.png';
 		}
 
-		$wantedAspectRatio = (float)($maxX / $maxY);
+		return $this->isCachedBigger($fileId);
+	}
 
-		//array for usable cached thumbnails
-		$possibleThumbnails = array();
+	/**
+	 * @brief check if a bigger version of thumbnail of file is cached
+	 * @param int $fileId fileId of the original image
+	 * @return string|false path to bigger thumbnail if it exists or false
+	*/
+	private function isCachedBigger($fileId) {
 
-		$allThumbnails = $this->userView->getDirectoryContent($previewPath);
-		foreach ($allThumbnails as $thumbnail) {
-			$name = rtrim($thumbnail['name'], '.png');
-			$size = explode('-', $name);
-			$x = (int)$size[0];
-			$y = (int)$size[1];
-
-			$aspectRatio = (float)($x / $y);
-			if ($aspectRatio !== $wantedAspectRatio) {
-				continue;
-			}
-
-			if ($x < $maxX || $y < $maxY) {
-				if ($scalingUp) {
-					$scalefactor = $maxX / $x;
-					if ($scalefactor > $maxScaleFactor) {
-						continue;
-					}
-				} else {
-					continue;
-				}
-			}
-			$possibleThumbnails[$x] = $thumbnail['path'];
-		}
-
-		if (count($possibleThumbnails) === 0) {
+		if (is_null($fileId)) {
 			return false;
 		}
 
-		if (count($possibleThumbnails) === 1) {
-			return current($possibleThumbnails);
-		}
+		$maxX = $this->getMaxX();
 
-		ksort($possibleThumbnails);
-
-		if (key(reset($possibleThumbnails)) > $maxX) {
-			return current(reset($possibleThumbnails));
-		}
-
-		if (key(end($possibleThumbnails)) < $maxX) {
-			return current(end($possibleThumbnails));
-		}
+		//array for usable cached thumbnails
+		$possibleThumbnails = $this->getPossibleThumbnails($fileId);
 
 		foreach ($possibleThumbnails as $width => $path) {
 			if ($width < $maxX) {
@@ -397,6 +361,72 @@ class Preview {
 				return $path;
 			}
 		}
+
+		return false;
+	}
+
+	/**
+	 * @brief get possible bigger thumbnails of the given image
+	 * @param int $fileId fileId of the original image
+	 * @return array of paths to bigger thumbnails
+	*/
+	private function getPossibleThumbnails($fileId) {
+
+		if (is_null($fileId)) {
+			return array();
+		}
+
+		$previewPath = $this->getThumbnailsFolder() . '/' . $fileId . '/';
+
+		$wantedAspectRatio = (float) ($this->getMaxX() / $this->getMaxY());
+
+		//array for usable cached thumbnails
+		$possibleThumbnails = array();
+
+		$allThumbnails = $this->userView->getDirectoryContent($previewPath);
+		foreach ($allThumbnails as $thumbnail) {
+			$name = rtrim($thumbnail['name'], '.png');
+			list($x, $y, $aspectRatio) = $this->getDimensionsFromFilename($name);
+
+			if (abs($aspectRatio - $wantedAspectRatio) >= 0.000001
+				|| $this->unscalable($x, $y)
+			) {
+				continue;
+			}
+			$possibleThumbnails[$x] = $thumbnail['path'];
+		}
+
+		ksort($possibleThumbnails);
+
+		return $possibleThumbnails;
+	}
+
+	private function getDimensionsFromFilename($name) {
+			$size = explode('-', $name);
+			$x = (int) $size[0];
+			$y = (int) $size[1];
+			$aspectRatio = (float) ($x / $y);
+			return array($x, $y, $aspectRatio);
+	}
+
+	private function unscalable($x, $y) {
+		
+		$maxX = $this->getMaxX();
+		$maxY = $this->getMaxY();
+		$scalingUp = $this->getScalingUp();
+		$maxScaleFactor = $this->getMaxScaleFactor();
+		
+		if ($x < $maxX || $y < $maxY) {
+			if ($scalingUp) {
+				$scalefactor = $maxX / $x;
+				if ($scalefactor > $maxScaleFactor) {
+					return true;
+				}
+			} else {
+				return true;
+			}
+		}
+		return false;
 	}
 
 	/**
@@ -420,7 +450,7 @@ class Preview {
 		}
 		$fileId = $fileInfo->getId();
 
-		$cached = $this->isCached();
+		$cached = $this->isCached($fileId);
 
 		if ($cached) {
 			$stream = $this->userView->fopen($cached, 'r');
@@ -434,13 +464,14 @@ class Preview {
 		if (is_null($this->preview)) {
 			$preview = null;
 
-			foreach (self::$providers as $supportedMimetype => $provider) {
-				if (!preg_match($supportedMimetype, $this->mimetype)) {
+			foreach (self::$providers as $supportedMimeType => $provider) {
+				if (!preg_match($supportedMimeType, $this->mimeType)) {
 					continue;
 				}
 
 				\OC_Log::write('core', 'Generating preview for "' . $file . '" with "' . get_class($provider) . '"', \OC_Log::DEBUG);
 
+				/** @var $provider Provider */
 				$preview = $provider->getThumbnail($file, $maxX, $maxY, $scalingUp, $this->fileView);
 
 				if (!($preview instanceof \OC_Image)) {
@@ -484,7 +515,6 @@ class Preview {
 			$this->getPreview();
 		}
 		$this->preview->show('image/png');
-		return;
 	}
 
 	/**
@@ -493,7 +523,6 @@ class Preview {
 	 */
 	public function show() {
 		$this->showPreview();
-		return;
 	}
 
 	/**
@@ -505,7 +534,7 @@ class Preview {
 		$x = $this->getMaxX();
 		$y = $this->getMaxY();
 		$scalingUp = $this->getScalingUp();
-		$maxscalefactor = $this->getMaxScaleFactor();
+		$maxScaleFactor = $this->getMaxScaleFactor();
 
 		if (!($image instanceof \OC_Image)) {
 			\OC_Log::write('core', '$this->preview is not an instance of OC_Image', \OC_Log::DEBUG);
@@ -514,16 +543,16 @@ class Preview {
 
 		$image->fixOrientation();
 
-		$realx = (int)$image->width();
-		$realy = (int)$image->height();
+		$realX = (int)$image->width();
+		$realY = (int)$image->height();
 
-		if ($x === $realx && $y === $realy) {
+		if ($x === $realX && $y === $realY) {
 			$this->preview = $image;
 			return;
 		}
 
-		$factorX = $x / $realx;
-		$factorY = $y / $realy;
+		$factorX = $x / $realX;
+		$factorY = $y / $realY;
 
 		if ($factorX >= $factorY) {
 			$factor = $factorX;
@@ -537,25 +566,25 @@ class Preview {
 			}
 		}
 
-		if (!is_null($maxscalefactor)) {
-			if ($factor > $maxscalefactor) {
-				\OC_Log::write('core', 'scalefactor reduced from ' . $factor . ' to ' . $maxscalefactor, \OC_Log::DEBUG);
-				$factor = $maxscalefactor;
+		if (!is_null($maxScaleFactor)) {
+			if ($factor > $maxScaleFactor) {
+				\OC_Log::write('core', 'scale factor reduced from ' . $factor . ' to ' . $maxScaleFactor, \OC_Log::DEBUG);
+				$factor = $maxScaleFactor;
 			}
 		}
 
-		$newXsize = (int)($realx * $factor);
-		$newYsize = (int)($realy * $factor);
+		$newXSize = (int)($realX * $factor);
+		$newYSize = (int)($realY * $factor);
 
-		$image->preciseResize($newXsize, $newYsize);
+		$image->preciseResize($newXSize, $newYSize);
 
-		if ($newXsize === $x && $newYsize === $y) {
+		if ($newXSize === $x && $newYSize === $y) {
 			$this->preview = $image;
 			return;
 		}
 
-		if ($newXsize >= $x && $newYsize >= $y) {
-			$cropX = floor(abs($x - $newXsize) * 0.5);
+		if ($newXSize >= $x && $newYSize >= $y) {
+			$cropX = floor(abs($x - $newXSize) * 0.5);
 			//don't crop previews on the Y axis, this sucks if it's a document.
 			//$cropY = floor(abs($y - $newYsize) * 0.5);
 			$cropY = 0;
@@ -566,36 +595,36 @@ class Preview {
 			return;
 		}
 
-		if ($newXsize < $x || $newYsize < $y) {
-			if ($newXsize > $x) {
-				$cropX = floor(($newXsize - $x) * 0.5);
-				$image->crop($cropX, 0, $x, $newYsize);
+		if ($newXSize < $x || $newYSize < $y) {
+			if ($newXSize > $x) {
+				$cropX = floor(($newXSize - $x) * 0.5);
+				$image->crop($cropX, 0, $x, $newYSize);
 			}
 
-			if ($newYsize > $y) {
-				$cropY = floor(($newYsize - $y) * 0.5);
-				$image->crop(0, $cropY, $newXsize, $y);
+			if ($newYSize > $y) {
+				$cropY = floor(($newYSize - $y) * 0.5);
+				$image->crop(0, $cropY, $newXSize, $y);
 			}
 
-			$newXsize = (int)$image->width();
-			$newYsize = (int)$image->height();
+			$newXSize = (int)$image->width();
+			$newYSize = (int)$image->height();
 
 			//create transparent background layer
-			$backgroundlayer = imagecreatetruecolor($x, $y);
-			$white = imagecolorallocate($backgroundlayer, 255, 255, 255);
-			imagefill($backgroundlayer, 0, 0, $white);
+			$backgroundLayer = imagecreatetruecolor($x, $y);
+			$white = imagecolorallocate($backgroundLayer, 255, 255, 255);
+			imagefill($backgroundLayer, 0, 0, $white);
 
 			$image = $image->resource();
 
-			$mergeX = floor(abs($x - $newXsize) * 0.5);
-			$mergeY = floor(abs($y - $newYsize) * 0.5);
+			$mergeX = floor(abs($x - $newXSize) * 0.5);
+			$mergeY = floor(abs($y - $newYSize) * 0.5);
 
-			imagecopy($backgroundlayer, $image, $mergeX, $mergeY, 0, 0, $newXsize, $newYsize);
+			imagecopy($backgroundLayer, $image, $mergeX, $mergeY, 0, 0, $newXSize, $newYSize);
 
 			//$black = imagecolorallocate(0,0,0);
 			//imagecolortransparent($transparentlayer, $black);
 
-			$image = new \OC_Image($backgroundlayer);
+			$image = new \OC_Image($backgroundLayer);
 
 			$this->preview = $image;
 			return;
@@ -630,6 +659,7 @@ class Preview {
 			$class = $provider['class'];
 			$options = $provider['options'];
 
+			/** @var $object Provider */
 			$object = new $class($options);
 
 			self::$providers[$object->getMimeType()] = $object;
@@ -676,9 +706,9 @@ class Preview {
 	}
 
 	/**
-	 * @param string $mimetype
+	 * @param string $mimeType
 	 */
-	public static function isMimeSupported($mimetype) {
+	public static function isMimeSupported($mimeType) {
 		if (!\OC_Config::getValue('enable_previews', true)) {
 			return false;
 		}
@@ -690,8 +720,8 @@ class Preview {
 
 		//remove last element because it has the mimetype *
 		$providers = array_slice(self::$providers, 0, -1);
-		foreach ($providers as $supportedMimetype => $provider) {
-			if (preg_match($supportedMimetype, $mimetype)) {
+		foreach ($providers as $supportedMimeType => $provider) {
+			if (preg_match($supportedMimeType, $mimeType)) {
 				return true;
 			}
 		}
diff --git a/tests/lib/preview.php b/tests/lib/preview.php
index 353b66fd6d..4ef61fb825 100644
--- a/tests/lib/preview.php
+++ b/tests/lib/preview.php
@@ -10,66 +10,73 @@ namespace Test;
 
 class Preview extends \PHPUnit_Framework_TestCase {
 
+	/**
+	 * @var string
+	 */
+	private $user;
+
+	/**
+	 * @var \OC\Files\View
+	 */
+	private $rootView;
+
+	public function setUp() {
+		$this->user = $this->initFS();
+
+		$this->rootView = new \OC\Files\View('');
+		$this->rootView->mkdir('/'.$this->user);
+		$this->rootView->mkdir('/'.$this->user.'/files');
+	}
+
 	public function testIsPreviewDeleted() {
-		$user = $this->initFS();
 
-		$rootView = new \OC\Files\View('');
-		$rootView->mkdir('/'.$user);
-		$rootView->mkdir('/'.$user.'/files');
+		$sampleFile = '/'.$this->user.'/files/test.txt';
 
-		$samplefile = '/'.$user.'/files/test.txt';
-
-		$rootView->file_put_contents($samplefile, 'dummy file data');
+		$this->rootView->file_put_contents($sampleFile, 'dummy file data');
 		
 		$x = 50;
 		$y = 50;
 
-		$preview = new \OC\Preview($user, 'files/', 'test.txt', $x, $y);
+		$preview = new \OC\Preview($this->user, 'files/', 'test.txt', $x, $y);
 		$preview->getPreview();
 
-		$fileinfo = $rootView->getFileInfo($samplefile);
-		$fileid = $fileinfo['fileid'];
+		$fileInfo = $this->rootView->getFileInfo($sampleFile);
+		$fileId = $fileInfo['fileid'];
 
-		$thumbcachefile = '/' . $user . '/' . \OC\Preview::THUMBNAILS_FOLDER . '/' . $fileid . '/' . $x . '-' . $y . '.png';
+		$thumbCacheFile = '/' . $this->user . '/' . \OC\Preview::THUMBNAILS_FOLDER . '/' . $fileId . '/' . $x . '-' . $y . '.png';
 		
-		$this->assertEquals($rootView->file_exists($thumbcachefile), true);
+		$this->assertEquals($this->rootView->file_exists($thumbCacheFile), true);
 
 		$preview->deletePreview();
 
-		$this->assertEquals($rootView->file_exists($thumbcachefile), false);
+		$this->assertEquals($this->rootView->file_exists($thumbCacheFile), false);
 	}
 
 	public function testAreAllPreviewsDeleted() {
-		$user = $this->initFS();
 
-		$rootView = new \OC\Files\View('');
-		$rootView->mkdir('/'.$user);
-		$rootView->mkdir('/'.$user.'/files');
+		$sampleFile = '/'.$this->user.'/files/test.txt';
 
-		$samplefile = '/'.$user.'/files/test.txt';
-
-		$rootView->file_put_contents($samplefile, 'dummy file data');
+		$this->rootView->file_put_contents($sampleFile, 'dummy file data');
 		
 		$x = 50;
 		$y = 50;
 
-		$preview = new \OC\Preview($user, 'files/', 'test.txt', $x, $y);
+		$preview = new \OC\Preview($this->user, 'files/', 'test.txt', $x, $y);
 		$preview->getPreview();
 
-		$fileinfo = $rootView->getFileInfo($samplefile);
-		$fileid = $fileinfo['fileid'];
+		$fileInfo = $this->rootView->getFileInfo($sampleFile);
+		$fileId = $fileInfo['fileid'];
 		
-		$thumbcachefolder = '/' . $user . '/' . \OC\Preview::THUMBNAILS_FOLDER . '/' . $fileid . '/';
+		$thumbCacheFolder = '/' . $this->user . '/' . \OC\Preview::THUMBNAILS_FOLDER . '/' . $fileId . '/';
 		
-		$this->assertEquals($rootView->is_dir($thumbcachefolder), true);
+		$this->assertEquals($this->rootView->is_dir($thumbCacheFolder), true);
 
 		$preview->deleteAllPreviews();
 
-		$this->assertEquals($rootView->is_dir($thumbcachefolder), false);
+		$this->assertEquals($this->rootView->is_dir($thumbCacheFolder), false);
 	}
 
 	public function testIsMaxSizeWorking() {
-		$user = $this->initFS();
 
 		$maxX = 250;
 		$maxY = 250;
@@ -77,15 +84,11 @@ class Preview extends \PHPUnit_Framework_TestCase {
 		\OC_Config::setValue('preview_max_x', $maxX);
 		\OC_Config::setValue('preview_max_y', $maxY);
 
-		$rootView = new \OC\Files\View('');
-		$rootView->mkdir('/'.$user);
-		$rootView->mkdir('/'.$user.'/files');
+		$sampleFile = '/'.$this->user.'/files/test.txt';
 
-		$samplefile = '/'.$user.'/files/test.txt';
+		$this->rootView->file_put_contents($sampleFile, 'dummy file data');
 
-		$rootView->file_put_contents($samplefile, 'dummy file data');
-
-		$preview = new \OC\Preview($user, 'files/', 'test.txt', 1000, 1000);
+		$preview = new \OC\Preview($this->user, 'files/', 'test.txt', 1000, 1000);
 		$image = $preview->getPreview();
 
 		$this->assertEquals($image->width(), $maxX);
@@ -108,18 +111,13 @@ class Preview extends \PHPUnit_Framework_TestCase {
 	 * @dataProvider txtBlacklist
 	 */
 	public function testIsTransparent($extension, $data, $expectedResult) {
-		$user = $this->initFS();
-
-		$rootView = new \OC\Files\View('');
-		$rootView->mkdir('/'.$user);
-		$rootView->mkdir('/'.$user.'/files');
 
 		$x = 32;
 		$y = 32;
 
-		$sample = '/'.$user.'/files/test.'.$extension;
-		$rootView->file_put_contents($sample, $data);
-		$preview = new \OC\Preview($user, 'files/', 'test.'.$extension, $x, $y);
+		$sample = '/'.$this->user.'/files/test.'.$extension;
+		$this->rootView->file_put_contents($sample, $data);
+		$preview = new \OC\Preview($this->user, 'files/', 'test.'.$extension, $x, $y);
 		$image = $preview->getPreview();
 		$resource = $image->resource();
 
@@ -133,6 +131,64 @@ class Preview extends \PHPUnit_Framework_TestCase {
 		);
 	}
 
+	public function testCreationFromCached() {
+
+		$sampleFile = '/'.$this->user.'/files/test.txt';
+
+		$this->rootView->file_put_contents($sampleFile, 'dummy file data');
+
+		// create base preview
+		$x = 150;
+		$y = 150;
+
+		$preview = new \OC\Preview($this->user, 'files/', 'test.txt', $x, $y);
+		$preview->getPreview();
+
+		$fileInfo = $this->rootView->getFileInfo($sampleFile);
+		$fileId = $fileInfo['fileid'];
+
+		$thumbCacheFile = '/' . $this->user . '/' . \OC\Preview::THUMBNAILS_FOLDER . '/' . $fileId . '/' . $x . '-' . $y . '.png';
+
+		$this->assertEquals($this->rootView->file_exists($thumbCacheFile), true);
+
+
+		// create smaller previews
+		$preview = new \OC\Preview($this->user, 'files/', 'test.txt', 50, 50);
+		$isCached = $preview->isCached($fileId);
+
+		$this->assertEquals($this->user . '/' . \OC\Preview::THUMBNAILS_FOLDER . '/' . $fileId . '/150-150.png', $isCached);
+	}
+
+	/*
+	public function testScalingUp() {
+
+		$sampleFile = '/'.$this->user.'/files/test.txt';
+
+		$this->rootView->file_put_contents($sampleFile, 'dummy file data');
+
+		// create base preview
+		$x = 150;
+		$y = 150;
+
+		$preview = new \OC\Preview($this->user, 'files/', 'test.txt', $x, $y);
+		$preview->getPreview();
+
+		$fileInfo = $this->rootView->getFileInfo($sampleFile);
+		$fileId = $fileInfo['fileid'];
+
+		$thumbCacheFile = '/' . $this->user . '/' . \OC\Preview::THUMBNAILS_FOLDER . '/' . $fileId . '/' . $x . '-' . $y . '.png';
+
+		$this->assertEquals($this->rootView->file_exists($thumbCacheFile), true);
+
+
+		// create bigger previews - with scale up
+		$preview = new \OC\Preview($this->user, 'files/', 'test.txt', 250, 250);
+		$isCached = $preview->isCached($fileId);
+
+		$this->assertEquals($this->user . '/' . \OC\Preview::THUMBNAILS_FOLDER . '/' . $fileId . '/150-150.png', $isCached);
+	}
+	*/
+
 	private function initFS() {
 		// create a new user with his own filesystem view
 		// this gets called by each test in this test class