server/lib/private/Preview/Generator.php

<?php
/**
 * @copyright Copyright (c) 2016, Roeland Jago Douma <roeland@famdouma.nl>
 *
 * @author Roeland Jago Douma <roeland@famdouma.nl>
 *
 * @license GNU AGPL version 3 or any later version
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Affero General Public License as
 * published by the Free Software Foundation, either version 3 of the
 * License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Affero General Public License for more details.
 *
 * You should have received a copy of the GNU Affero General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 *
 */

namespace OC\Preview;

use OCP\Files\File;
use OCP\Files\IAppData;
use OCP\Files\NotFoundException;
use OCP\Files\NotPermittedException;
use OCP\Files\SimpleFS\ISimpleFile;
use OCP\Files\SimpleFS\ISimpleFolder;
use OCP\IConfig;
use OCP\IImage;
use OCP\IPreview;
use OCP\Preview\IProvider;
use Symfony\Component\EventDispatcher\EventDispatcherInterface;
use Symfony\Component\EventDispatcher\GenericEvent;

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) {
		$this->eventDispatcher->dispatch(
			IPreview::EVENT,
			new GenericEvent($file,[
				'width' => $width,
				'height' => $height,
				'crop' => $crop,
				'mode' => $mode
			])
		);

		if ($mimeType === null) {
			$mimeType = $file->getMimeType();
		}
		if (!$this->previewManager->isMimeSupported($mimeType)) {
			throw new NotFoundException();
		}

		$previewFolder = $this->getPreviewFolder($file);

		// Get the max preview and infer the max preview sizes from that
		$maxPreview = $this->getMaxPreview($previewFolder, $file, $mimeType);
		list($maxWidth, $maxHeight) = $this->getPreviewSize($maxPreview);

		// Calculate the preview size
		list($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) {
			return $maxPreview;
		}

		// Try to get a cached preview. Else generate (and store) one
		try {
			$file = $this->getCachedPreview($previewFolder, $width, $height, $crop);
		} catch (NotFoundException $e) {
			$file = $this->generatePreview($previewFolder, $maxPreview, $width, $height, $crop, $maxWidth, $maxHeight);
		}

		return $file;
	}

	/**
	 * @param ISimpleFolder $previewFolder
	 * @param File $file
	 * @param string $mimeType
	 * @return ISimpleFile
	 * @throws NotFoundException
	 */
	private function getMaxPreview(ISimpleFolder $previewFolder, File $file, $mimeType) {
		$nodes = $previewFolder->getDirectoryListing();

		foreach ($nodes as $node) {
			if (strpos($node->getName(), 'max')) {
				return $node;
			}
		}

		$previewProviders = $this->previewManager->getProviders();
		foreach ($previewProviders as $supportedMimeType => $providers) {
			if (!preg_match($supportedMimeType, $mimeType)) {
				continue;
			}

			foreach ($providers as $provider) {
				$provider = $this->helper->getProvider($provider);
				if (!($provider instanceof IProvider)) {
					continue;
				}

				$maxWidth = (int)$this->config->getSystemValue('preview_max_x', 2048);
				$maxHeight = (int)$this->config->getSystemValue('preview_max_y', 2048);

				$preview = $this->helper->getThumbnail($provider, $file, $maxWidth, $maxHeight);

				if (!($preview instanceof IImage)) {
					continue;
				}

				$path = (string)$preview->width() . '-' . (string)$preview->height() . '-max.png';
				try {
					$file = $previewFolder->newFile($path);
					$file->putContent($preview->data());
				} catch (NotPermittedException $e) {
					throw new NotFoundException();
				}

				return $file;
			}
		}

		throw new NotFoundException();
	}

	/**
	 * @param ISimpleFile $file
	 * @return int[]
	 */
	private function getPreviewSize(ISimpleFile $file) {
		$size = explode('-', $file->getName());
		return [(int)$size[0], (int)$size[1]];
	}

	/**
	 * @param int $width
	 * @param int $height
	 * @param bool $crop
	 * @return string
	 */
	private function generatePath($width, $height, $crop) {
		$path = (string)$width . '-' . (string)$height;
		if ($crop) {
			$path .= '-crop';
		}
		$path .= '.png';
		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 ($width === -1) {
				$width = $height / $ratio;
			}
			if ($height === -1) {
				$height = $width * $ratio;
			}

			$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 / $ratio;
				}
			} else if ($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 two
			 */
			$pow2height = 2 ** ceil(log($height) / log(2));
			$pow2width = 2 ** ceil(log($width) / log(2));

			$ratioH = $height / $pow2height;
			$ratioW = $width / $pow2width;

			if ($ratioH < $ratioW) {
				$width = $pow2width;
				$height /= $ratioW;
			} else {
				$height = $pow2height;
				$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
	 * @return ISimpleFile
	 * @throws NotFoundException
	 * @throws \InvalidArgumentException if the preview would be invalid (in case the original image is invalid)
	 */
	private function generatePreview(ISimpleFolder $previewFolder, ISimpleFile $maxPreview, $width, $height, $crop, $maxWidth, $maxHeight) {
		$preview = $this->helper->getImage($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;
				}
				$preview->preciseResize(round($scaleW), round($scaleH));
			}
			$cropX = floor(abs($width - $preview->width()) * 0.5);
			$cropY = 0;
			$preview->crop($cropX, $cropY, $width, $height);
		} else {
			$preview->resize(max($width, $height));
		}


		$path = $this->generatePath($width, $height, $crop);
		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
	 * @return ISimpleFile
	 *
	 * @throws NotFoundException
	 */
	private function getCachedPreview(ISimpleFolder $previewFolder, $width, $height, $crop) {
		$path = $this->generatePath($width, $height, $crop);

		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;
	}
}