nextcloud / server

lib/private/Preview/Generator.php

Indentation +432 added lines, -432 removed lines

@@ -43,450 +43,450 @@
 
 class Generator {
 
-	/** @var IPreview */
-	private $previewManager;
-	/** @var IConfig */
-	private $config;
-	/** @var IAppData */
-	private $appData;
-	/** @var GeneratorHelper */
-	private $helper;
-	/** @var EventDispatcherInterface */
-	private $eventDispatcher;
-
-	/**
-	 * @param IConfig $config
-	 * @param IPreview $previewManager
-	 * @param IAppData $appData
-	 * @param GeneratorHelper $helper
-	 * @param EventDispatcherInterface $eventDispatcher
-	 */
-	public function __construct(
-		IConfig $config,
-		IPreview $previewManager,
-		IAppData $appData,
-		GeneratorHelper $helper,
-		EventDispatcherInterface $eventDispatcher
-	) {
-		$this->config = $config;
-		$this->previewManager = $previewManager;
-		$this->appData = $appData;
-		$this->helper = $helper;
-		$this->eventDispatcher = $eventDispatcher;
-	}
-
-	/**
-	 * Returns a preview of a file
-	 *
-	 * The cache is searched first and if nothing usable was found then a preview is
-	 * generated by one of the providers
-	 *
-	 * @param File $file
-	 * @param int $width
-	 * @param int $height
-	 * @param bool $crop
-	 * @param string $mode
-	 * @param string $mimeType
-	 * @return ISimpleFile
-	 * @throws NotFoundException
-	 * @throws \InvalidArgumentException if the preview would be invalid (in case the original image is invalid)
-	 */
-	public function getPreview(File $file, $width = -1, $height = -1, $crop = false, $mode = IPreview::MODE_FILL, $mimeType = null) {
-		$specification = [
-			'width' => $width,
-			'height' => $height,
-			'crop' => $crop,
-			'mode' => $mode,
-		];
-		$this->eventDispatcher->dispatch(
-			IPreview::EVENT,
-			new GenericEvent($file, $specification)
-		);
-
-		// since we only ask for one preview, and the generate method return the last one it created, it returns the one we want
-		return $this->generatePreviews($file, [$specification], $mimeType);
-	}
-
-	/**
-	 * Generates previews of a file
-	 *
-	 * @param File $file
-	 * @param array $specifications
-	 * @param string $mimeType
-	 * @return ISimpleFile the last preview that was generated
-	 * @throws NotFoundException
-	 * @throws \InvalidArgumentException if the preview would be invalid (in case the original image is invalid)
-	 */
-	public function generatePreviews(File $file, array $specifications, $mimeType = null) {
-		//Make sure that we can read the file
-		if (!$file->isReadable()) {
-			throw new NotFoundException('Cannot read file');
-		}
-
-		if ($mimeType === null) {
-			$mimeType = $file->getMimeType();
-		}
-
-		$previewFolder = $this->getPreviewFolder($file);
-
-		$previewVersion = '';
-		if ($file instanceof IVersionedPreviewFile) {
-			$previewVersion = $file->getPreviewVersion() . '-';
-		}
-
-		// Get the max preview and infer the max preview sizes from that
-		$maxPreview = $this->getMaxPreview($previewFolder, $file, $mimeType, $previewVersion);
-		$maxPreviewImage = null; // only load the image when we need it
-		if ($maxPreview->getSize() === 0) {
-			$maxPreview->delete();
-			throw new NotFoundException('Max preview size 0, invalid!');
-		}
-
-		[$maxWidth, $maxHeight] = $this->getPreviewSize($maxPreview, $previewVersion);
-
-		$preview = null;
-
-		foreach ($specifications as $specification) {
-			$width = $specification['width'] ?? -1;
-			$height = $specification['height'] ?? -1;
-			$crop = $specification['crop'] ?? false;
-			$mode = $specification['mode'] ?? IPreview::MODE_FILL;
-
-			// If both width and height are -1 we just want the max preview
-			if ($width === -1 && $height === -1) {
-				$width = $maxWidth;
-				$height = $maxHeight;
-			}
-
-			// Calculate the preview size
-			[$width, $height] = $this->calculateSize($width, $height, $crop, $mode, $maxWidth, $maxHeight);
-
-			// No need to generate a preview that is just the max preview
-			if ($width === $maxWidth && $height === $maxHeight) {
-				// ensure correct return value if this was the last one
-				$preview = $maxPreview;
-				continue;
-			}
-
-			// Try to get a cached preview. Else generate (and store) one
-			try {
-				try {
-					$preview = $this->getCachedPreview($previewFolder, $width, $height, $crop, $maxPreview->getMimeType(), $previewVersion);
-				} catch (NotFoundException $e) {
-					if (!$this->previewManager->isMimeSupported($mimeType)) {
-						throw new NotFoundException();
-					}
-
-					if ($maxPreviewImage === null) {
-						$maxPreviewImage = $this->helper->getImage($maxPreview);
-					}
-
-					$preview = $this->generatePreview($previewFolder, $maxPreviewImage, $width, $height, $crop, $maxWidth, $maxHeight, $previewVersion);
-				}
-			} catch (\InvalidArgumentException $e) {
-				throw new NotFoundException("", 0, $e);
-			}
-
-			if ($preview->getSize() === 0) {
-				$preview->delete();
-				throw new NotFoundException('Cached preview size 0, invalid!');
-			}
-		}
-
-		// Free memory being used by the embedded image resource.  Without this the image is kept in memory indefinitely.
-		// Garbage Collection does NOT free this memory.  We have to do it ourselves.
-		if ($maxPreviewImage instanceof \OC_Image) {
-			$maxPreviewImage->destroy();
-		}
-
-		return $preview;
-	}
-
-	/**
-	 * @param ISimpleFolder $previewFolder
-	 * @param File $file
-	 * @param string $mimeType
-	 * @param string $prefix
-	 * @return ISimpleFile
-	 * @throws NotFoundException
-	 */
-	private function getMaxPreview(ISimpleFolder $previewFolder, File $file, $mimeType, $prefix) {
-		$nodes = $previewFolder->getDirectoryListing();
-
-		foreach ($nodes as $node) {
-			$name = $node->getName();
-			if (($prefix === '' || strpos($name, $prefix) === 0) && strpos($name, 'max')) {
-				return $node;
-			}
-		}
-
-		$previewProviders = $this->previewManager->getProviders();
-		foreach ($previewProviders as $supportedMimeType => $providers) {
-			if (!preg_match($supportedMimeType, $mimeType)) {
-				continue;
-			}
-
-			foreach ($providers as $providerClosure) {
-				$provider = $this->helper->getProvider($providerClosure);
-				if (!($provider instanceof IProviderV2)) {
-					continue;
-				}
-
-				if (!$provider->isAvailable($file)) {
-					continue;
-				}
-
-				$maxWidth = (int)$this->config->getSystemValue('preview_max_x', 4096);
-				$maxHeight = (int)$this->config->getSystemValue('preview_max_y', 4096);
-
-				$preview = $this->helper->getThumbnail($provider, $file, $maxWidth, $maxHeight);
-
-				if (!($preview instanceof IImage)) {
-					continue;
-				}
-
-				// Try to get the extention.
-				try {
-					$ext = $this->getExtention($preview->dataMimeType());
-				} catch (\InvalidArgumentException $e) {
-					// Just continue to the next iteration if this preview doesn't have a valid mimetype
-					continue;
-				}
-
-				$path = $prefix . (string)$preview->width() . '-' . (string)$preview->height() . '-max.' . $ext;
-				try {
-					$file = $previewFolder->newFile($path);
-					$file->putContent($preview->data());
-				} catch (NotPermittedException $e) {
-					throw new NotFoundException();
-				}
-
-				return $file;
-			}
-		}
-
-		throw new NotFoundException();
-	}
-
-	/**
-	 * @param ISimpleFile $file
-	 * @param string $prefix
-	 * @return int[]
-	 */
-	private function getPreviewSize(ISimpleFile $file, string $prefix = '') {
-		$size = explode('-', substr($file->getName(), strlen($prefix)));
-		return [(int)$size[0], (int)$size[1]];
-	}
-
-	/**
-	 * @param int $width
-	 * @param int $height
-	 * @param bool $crop
-	 * @param string $mimeType
-	 * @param string $prefix
-	 * @return string
-	 */
-	private function generatePath($width, $height, $crop, $mimeType, $prefix) {
-		$path = $prefix . (string)$width . '-' . (string)$height;
-		if ($crop) {
-			$path .= '-crop';
-		}
-
-		$ext = $this->getExtention($mimeType);
-		$path .= '.' . $ext;
-		return $path;
-	}
-
-
-	/**
-	 * @param int $width
-	 * @param int $height
-	 * @param bool $crop
-	 * @param string $mode
-	 * @param int $maxWidth
-	 * @param int $maxHeight
-	 * @return int[]
-	 */
-	private function calculateSize($width, $height, $crop, $mode, $maxWidth, $maxHeight) {
-
-		/*
+    /** @var IPreview */
+    private $previewManager;
+    /** @var IConfig */
+    private $config;
+    /** @var IAppData */
+    private $appData;
+    /** @var GeneratorHelper */
+    private $helper;
+    /** @var EventDispatcherInterface */
+    private $eventDispatcher;
+
+    /**
+     * @param IConfig $config
+     * @param IPreview $previewManager
+     * @param IAppData $appData
+     * @param GeneratorHelper $helper
+     * @param EventDispatcherInterface $eventDispatcher
+     */
+    public function __construct(
+        IConfig $config,
+        IPreview $previewManager,
+        IAppData $appData,
+        GeneratorHelper $helper,
+        EventDispatcherInterface $eventDispatcher
+    ) {
+        $this->config = $config;
+        $this->previewManager = $previewManager;
+        $this->appData = $appData;
+        $this->helper = $helper;
+        $this->eventDispatcher = $eventDispatcher;
+    }
+
+    /**
+     * Returns a preview of a file
+     *
+     * The cache is searched first and if nothing usable was found then a preview is
+     * generated by one of the providers
+     *
+     * @param File $file
+     * @param int $width
+     * @param int $height
+     * @param bool $crop
+     * @param string $mode
+     * @param string $mimeType
+     * @return ISimpleFile
+     * @throws NotFoundException
+     * @throws \InvalidArgumentException if the preview would be invalid (in case the original image is invalid)
+     */
+    public function getPreview(File $file, $width = -1, $height = -1, $crop = false, $mode = IPreview::MODE_FILL, $mimeType = null) {
+        $specification = [
+            'width' => $width,
+            'height' => $height,
+            'crop' => $crop,
+            'mode' => $mode,
+        ];
+        $this->eventDispatcher->dispatch(
+            IPreview::EVENT,
+            new GenericEvent($file, $specification)
+        );
+
+        // since we only ask for one preview, and the generate method return the last one it created, it returns the one we want
+        return $this->generatePreviews($file, [$specification], $mimeType);
+    }
+
+    /**
+     * Generates previews of a file
+     *
+     * @param File $file
+     * @param array $specifications
+     * @param string $mimeType
+     * @return ISimpleFile the last preview that was generated
+     * @throws NotFoundException
+     * @throws \InvalidArgumentException if the preview would be invalid (in case the original image is invalid)
+     */
+    public function generatePreviews(File $file, array $specifications, $mimeType = null) {
+        //Make sure that we can read the file
+        if (!$file->isReadable()) {
+            throw new NotFoundException('Cannot read file');
+        }
+
+        if ($mimeType === null) {
+            $mimeType = $file->getMimeType();
+        }
+
+        $previewFolder = $this->getPreviewFolder($file);
+
+        $previewVersion = '';
+        if ($file instanceof IVersionedPreviewFile) {
+            $previewVersion = $file->getPreviewVersion() . '-';
+        }
+
+        // Get the max preview and infer the max preview sizes from that
+        $maxPreview = $this->getMaxPreview($previewFolder, $file, $mimeType, $previewVersion);
+        $maxPreviewImage = null; // only load the image when we need it
+        if ($maxPreview->getSize() === 0) {
+            $maxPreview->delete();
+            throw new NotFoundException('Max preview size 0, invalid!');
+        }
+
+        [$maxWidth, $maxHeight] = $this->getPreviewSize($maxPreview, $previewVersion);
+
+        $preview = null;
+
+        foreach ($specifications as $specification) {
+            $width = $specification['width'] ?? -1;
+            $height = $specification['height'] ?? -1;
+            $crop = $specification['crop'] ?? false;
+            $mode = $specification['mode'] ?? IPreview::MODE_FILL;
+
+            // If both width and height are -1 we just want the max preview
+            if ($width === -1 && $height === -1) {
+                $width = $maxWidth;
+                $height = $maxHeight;
+            }
+
+            // Calculate the preview size
+            [$width, $height] = $this->calculateSize($width, $height, $crop, $mode, $maxWidth, $maxHeight);
+
+            // No need to generate a preview that is just the max preview
+            if ($width === $maxWidth && $height === $maxHeight) {
+                // ensure correct return value if this was the last one
+                $preview = $maxPreview;
+                continue;
+            }
+
+            // Try to get a cached preview. Else generate (and store) one
+            try {
+                try {
+                    $preview = $this->getCachedPreview($previewFolder, $width, $height, $crop, $maxPreview->getMimeType(), $previewVersion);
+                } catch (NotFoundException $e) {
+                    if (!$this->previewManager->isMimeSupported($mimeType)) {
+                        throw new NotFoundException();
+                    }
+
+                    if ($maxPreviewImage === null) {
+                        $maxPreviewImage = $this->helper->getImage($maxPreview);
+                    }
+
+                    $preview = $this->generatePreview($previewFolder, $maxPreviewImage, $width, $height, $crop, $maxWidth, $maxHeight, $previewVersion);
+                }
+            } catch (\InvalidArgumentException $e) {
+                throw new NotFoundException("", 0, $e);
+            }
+
+            if ($preview->getSize() === 0) {
+                $preview->delete();
+                throw new NotFoundException('Cached preview size 0, invalid!');
+            }
+        }
+
+        // Free memory being used by the embedded image resource.  Without this the image is kept in memory indefinitely.
+        // Garbage Collection does NOT free this memory.  We have to do it ourselves.
+        if ($maxPreviewImage instanceof \OC_Image) {
+            $maxPreviewImage->destroy();
+        }
+
+        return $preview;
+    }
+
+    /**
+     * @param ISimpleFolder $previewFolder
+     * @param File $file
+     * @param string $mimeType
+     * @param string $prefix
+     * @return ISimpleFile
+     * @throws NotFoundException
+     */
+    private function getMaxPreview(ISimpleFolder $previewFolder, File $file, $mimeType, $prefix) {
+        $nodes = $previewFolder->getDirectoryListing();
+
+        foreach ($nodes as $node) {
+            $name = $node->getName();
+            if (($prefix === '' || strpos($name, $prefix) === 0) && strpos($name, 'max')) {
+                return $node;
+            }
+        }
+
+        $previewProviders = $this->previewManager->getProviders();
+        foreach ($previewProviders as $supportedMimeType => $providers) {
+            if (!preg_match($supportedMimeType, $mimeType)) {
+                continue;
+            }
+
+            foreach ($providers as $providerClosure) {
+                $provider = $this->helper->getProvider($providerClosure);
+                if (!($provider instanceof IProviderV2)) {
+                    continue;
+                }
+
+                if (!$provider->isAvailable($file)) {
+                    continue;
+                }
+
+                $maxWidth = (int)$this->config->getSystemValue('preview_max_x', 4096);
+                $maxHeight = (int)$this->config->getSystemValue('preview_max_y', 4096);
+
+                $preview = $this->helper->getThumbnail($provider, $file, $maxWidth, $maxHeight);
+
+                if (!($preview instanceof IImage)) {
+                    continue;
+                }
+
+                // Try to get the extention.
+                try {
+                    $ext = $this->getExtention($preview->dataMimeType());
+                } catch (\InvalidArgumentException $e) {
+                    // Just continue to the next iteration if this preview doesn't have a valid mimetype
+                    continue;
+                }
+
+                $path = $prefix . (string)$preview->width() . '-' . (string)$preview->height() . '-max.' . $ext;
+                try {
+                    $file = $previewFolder->newFile($path);
+                    $file->putContent($preview->data());
+                } catch (NotPermittedException $e) {
+                    throw new NotFoundException();
+                }
+
+                return $file;
+            }
+        }
+
+        throw new NotFoundException();
+    }
+
+    /**
+     * @param ISimpleFile $file
+     * @param string $prefix
+     * @return int[]
+     */
+    private function getPreviewSize(ISimpleFile $file, string $prefix = '') {
+        $size = explode('-', substr($file->getName(), strlen($prefix)));
+        return [(int)$size[0], (int)$size[1]];
+    }
+
+    /**
+     * @param int $width
+     * @param int $height
+     * @param bool $crop
+     * @param string $mimeType
+     * @param string $prefix
+     * @return string
+     */
+    private function generatePath($width, $height, $crop, $mimeType, $prefix) {
+        $path = $prefix . (string)$width . '-' . (string)$height;
+        if ($crop) {
+            $path .= '-crop';
+        }
+
+        $ext = $this->getExtention($mimeType);
+        $path .= '.' . $ext;
+        return $path;
+    }
+
+
+    /**
+     * @param int $width
+     * @param int $height
+     * @param bool $crop
+     * @param string $mode
+     * @param int $maxWidth
+     * @param int $maxHeight
+     * @return int[]
+     */
+    private function calculateSize($width, $height, $crop, $mode, $maxWidth, $maxHeight) {
+
+        /*
 		 * If we are not cropping we have to make sure the requested image
 		 * respects the aspect ratio of the original.
 		 */
-		if (!$crop) {
-			$ratio = $maxHeight / $maxWidth;
+        if (!$crop) {
+            $ratio = $maxHeight / $maxWidth;
 
-			if ($width === -1) {
-				$width = $height / $ratio;
-			}
-			if ($height === -1) {
-				$height = $width * $ratio;
-			}
+            if ($width === -1) {
+                $width = $height / $ratio;
+            }
+            if ($height === -1) {
+                $height = $width * $ratio;
+            }
 
-			$ratioH = $height / $maxHeight;
-			$ratioW = $width / $maxWidth;
+            $ratioH = $height / $maxHeight;
+            $ratioW = $width / $maxWidth;
 
-			/*
+            /*
 			 * Fill means that the $height and $width are the max
 			 * Cover means min.
 			 */
-			if ($mode === IPreview::MODE_FILL) {
-				if ($ratioH > $ratioW) {
-					$height = $width * $ratio;
-				} else {
-					$width = $height / $ratio;
-				}
-			} elseif ($mode === IPreview::MODE_COVER) {
-				if ($ratioH > $ratioW) {
-					$width = $height / $ratio;
-				} else {
-					$height = $width * $ratio;
-				}
-			}
-		}
-
-		if ($height !== $maxHeight && $width !== $maxWidth) {
-			/*
+            if ($mode === IPreview::MODE_FILL) {
+                if ($ratioH > $ratioW) {
+                    $height = $width * $ratio;
+                } else {
+                    $width = $height / $ratio;
+                }
+            } elseif ($mode === IPreview::MODE_COVER) {
+                if ($ratioH > $ratioW) {
+                    $width = $height / $ratio;
+                } else {
+                    $height = $width * $ratio;
+                }
+            }
+        }
+
+        if ($height !== $maxHeight && $width !== $maxWidth) {
+            /*
 			 * Scale to the nearest power of four
 			 */
-			$pow4height = 4 ** ceil(log($height) / log(4));
-			$pow4width = 4 ** ceil(log($width) / log(4));
-
-			// Minimum size is 64
-			$pow4height = max($pow4height, 64);
-			$pow4width = max($pow4width, 64);
-
-			$ratioH = $height / $pow4height;
-			$ratioW = $width / $pow4width;
-
-			if ($ratioH < $ratioW) {
-				$width = $pow4width;
-				$height /= $ratioW;
-			} else {
-				$height = $pow4height;
-				$width /= $ratioH;
-			}
-		}
-
-		/*
+            $pow4height = 4 ** ceil(log($height) / log(4));
+            $pow4width = 4 ** ceil(log($width) / log(4));
+
+            // Minimum size is 64
+            $pow4height = max($pow4height, 64);
+            $pow4width = max($pow4width, 64);
+
+            $ratioH = $height / $pow4height;
+            $ratioW = $width / $pow4width;
+
+            if ($ratioH < $ratioW) {
+                $width = $pow4width;
+                $height /= $ratioW;
+            } else {
+                $height = $pow4height;
+                $width /= $ratioH;
+            }
+        }
+
+        /*
 		 * Make sure the requested height and width fall within the max
 		 * of the preview.
 		 */
-		if ($height > $maxHeight) {
-			$ratio = $height / $maxHeight;
-			$height = $maxHeight;
-			$width /= $ratio;
-		}
-		if ($width > $maxWidth) {
-			$ratio = $width / $maxWidth;
-			$width = $maxWidth;
-			$height /= $ratio;
-		}
-
-		return [(int)round($width), (int)round($height)];
-	}
-
-	/**
-	 * @param ISimpleFolder $previewFolder
-	 * @param ISimpleFile $maxPreview
-	 * @param int $width
-	 * @param int $height
-	 * @param bool $crop
-	 * @param int $maxWidth
-	 * @param int $maxHeight
-	 * @param string $prefix
-	 * @return ISimpleFile
-	 * @throws NotFoundException
-	 * @throws \InvalidArgumentException if the preview would be invalid (in case the original image is invalid)
-	 */
-	private function generatePreview(ISimpleFolder $previewFolder, IImage $maxPreview, $width, $height, $crop, $maxWidth, $maxHeight, $prefix) {
-		$preview = $maxPreview;
-		if (!$preview->valid()) {
-			throw new \InvalidArgumentException('Failed to generate preview, failed to load image');
-		}
-
-		if ($crop) {
-			if ($height !== $preview->height() && $width !== $preview->width()) {
-				//Resize
-				$widthR = $preview->width() / $width;
-				$heightR = $preview->height() / $height;
-
-				if ($widthR > $heightR) {
-					$scaleH = $height;
-					$scaleW = $maxWidth / $heightR;
-				} else {
-					$scaleH = $maxHeight / $widthR;
-					$scaleW = $width;
-				}
-				$preview = $preview->preciseResizeCopy((int)round($scaleW), (int)round($scaleH));
-			}
-			$cropX = (int)floor(abs($width - $preview->width()) * 0.5);
-			$cropY = (int)floor(abs($height - $preview->height()) * 0.5);
-			$preview = $preview->cropCopy($cropX, $cropY, $width, $height);
-		} else {
-			$preview = $maxPreview->resizeCopy(max($width, $height));
-		}
-
-
-		$path = $this->generatePath($width, $height, $crop, $preview->dataMimeType(), $prefix);
-		try {
-			$file = $previewFolder->newFile($path);
-			$file->putContent($preview->data());
-		} catch (NotPermittedException $e) {
-			throw new NotFoundException();
-		}
-
-		return $file;
-	}
-
-	/**
-	 * @param ISimpleFolder $previewFolder
-	 * @param int $width
-	 * @param int $height
-	 * @param bool $crop
-	 * @param string $mimeType
-	 * @param string $prefix
-	 * @return ISimpleFile
-	 *
-	 * @throws NotFoundException
-	 */
-	private function getCachedPreview(ISimpleFolder $previewFolder, $width, $height, $crop, $mimeType, $prefix) {
-		$path = $this->generatePath($width, $height, $crop, $mimeType, $prefix);
-
-		return $previewFolder->getFile($path);
-	}
-
-	/**
-	 * Get the specific preview folder for this file
-	 *
-	 * @param File $file
-	 * @return ISimpleFolder
-	 */
-	private function getPreviewFolder(File $file) {
-		try {
-			$folder = $this->appData->getFolder($file->getId());
-		} catch (NotFoundException $e) {
-			$folder = $this->appData->newFolder($file->getId());
-		}
-
-		return $folder;
-	}
-
-	/**
-	 * @param string $mimeType
-	 * @return null|string
-	 * @throws \InvalidArgumentException
-	 */
-	private function getExtention($mimeType) {
-		switch ($mimeType) {
-			case 'image/png':
-				return 'png';
-			case 'image/jpeg':
-				return 'jpg';
-			case 'image/gif':
-				return 'gif';
-			default:
-				throw new \InvalidArgumentException('Not a valid mimetype: "' . $mimeType . '"');
-		}
-	}
+        if ($height > $maxHeight) {
+            $ratio = $height / $maxHeight;
+            $height = $maxHeight;
+            $width /= $ratio;
+        }
+        if ($width > $maxWidth) {
+            $ratio = $width / $maxWidth;
+            $width = $maxWidth;
+            $height /= $ratio;
+        }
+
+        return [(int)round($width), (int)round($height)];
+    }
+
+    /**
+     * @param ISimpleFolder $previewFolder
+     * @param ISimpleFile $maxPreview
+     * @param int $width
+     * @param int $height
+     * @param bool $crop
+     * @param int $maxWidth
+     * @param int $maxHeight
+     * @param string $prefix
+     * @return ISimpleFile
+     * @throws NotFoundException
+     * @throws \InvalidArgumentException if the preview would be invalid (in case the original image is invalid)
+     */
+    private function generatePreview(ISimpleFolder $previewFolder, IImage $maxPreview, $width, $height, $crop, $maxWidth, $maxHeight, $prefix) {
+        $preview = $maxPreview;
+        if (!$preview->valid()) {
+            throw new \InvalidArgumentException('Failed to generate preview, failed to load image');
+        }
+
+        if ($crop) {
+            if ($height !== $preview->height() && $width !== $preview->width()) {
+                //Resize
+                $widthR = $preview->width() / $width;
+                $heightR = $preview->height() / $height;
+
+                if ($widthR > $heightR) {
+                    $scaleH = $height;
+                    $scaleW = $maxWidth / $heightR;
+                } else {
+                    $scaleH = $maxHeight / $widthR;
+                    $scaleW = $width;
+                }
+                $preview = $preview->preciseResizeCopy((int)round($scaleW), (int)round($scaleH));
+            }
+            $cropX = (int)floor(abs($width - $preview->width()) * 0.5);
+            $cropY = (int)floor(abs($height - $preview->height()) * 0.5);
+            $preview = $preview->cropCopy($cropX, $cropY, $width, $height);
+        } else {
+            $preview = $maxPreview->resizeCopy(max($width, $height));
+        }
+
+
+        $path = $this->generatePath($width, $height, $crop, $preview->dataMimeType(), $prefix);
+        try {
+            $file = $previewFolder->newFile($path);
+            $file->putContent($preview->data());
+        } catch (NotPermittedException $e) {
+            throw new NotFoundException();
+        }
+
+        return $file;
+    }
+
+    /**
+     * @param ISimpleFolder $previewFolder
+     * @param int $width
+     * @param int $height
+     * @param bool $crop
+     * @param string $mimeType
+     * @param string $prefix
+     * @return ISimpleFile
+     *
+     * @throws NotFoundException
+     */
+    private function getCachedPreview(ISimpleFolder $previewFolder, $width, $height, $crop, $mimeType, $prefix) {
+        $path = $this->generatePath($width, $height, $crop, $mimeType, $prefix);
+
+        return $previewFolder->getFile($path);
+    }
+
+    /**
+     * Get the specific preview folder for this file
+     *
+     * @param File $file
+     * @return ISimpleFolder
+     */
+    private function getPreviewFolder(File $file) {
+        try {
+            $folder = $this->appData->getFolder($file->getId());
+        } catch (NotFoundException $e) {
+            $folder = $this->appData->newFolder($file->getId());
+        }
+
+        return $folder;
+    }
+
+    /**
+     * @param string $mimeType
+     * @return null|string
+     * @throws \InvalidArgumentException
+     */
+    private function getExtention($mimeType) {
+        switch ($mimeType) {
+            case 'image/png':
+                return 'png';
+            case 'image/jpeg':
+                return 'jpg';
+            case 'image/gif':
+                return 'gif';
+            default:
+                throw new \InvalidArgumentException('Not a valid mimetype: "' . $mimeType . '"');
+        }
+    }
 }