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129 lines
3.6 KiB
PHP
129 lines
3.6 KiB
PHP
<?php
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/**
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* SPDX-FileCopyrightText: 2016-2024 Nextcloud GmbH and Nextcloud contributors
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* SPDX-FileCopyrightText: 2016 ownCloud, Inc.
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* SPDX-License-Identifier: AGPL-3.0-only
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*/
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namespace OC\Preview;
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use Imagick;
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use OCP\Files\File;
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use OCP\IImage;
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use Psr\Log\LoggerInterface;
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/**
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* Creates a PNG preview using ImageMagick via the PECL extension
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*
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* @package OC\Preview
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*/
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abstract class Bitmap extends ProviderV2 {
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/**
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* List of MIME types that this preview provider is allowed to process.
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*
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* These should correspond to the MIME types *identified* by Imagemagick
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* for files to be processed by this provider. These do / will not
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* necessarily need to match the MIME types stored in the database
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* (which are identified by IMimeTypeDetector).
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*
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* @return string Regular expression
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*/
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abstract protected function getAllowedMimeTypes(): string;
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/**
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* {@inheritDoc}
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*/
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public function getThumbnail(File $file, int $maxX, int $maxY): ?IImage {
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$tmpPath = $this->getLocalFile($file);
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if ($tmpPath === false) {
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\OC::$server->get(LoggerInterface::class)->error(
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'Failed to get thumbnail for: ' . $file->getPath(),
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['app' => 'core']
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);
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return null;
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}
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// Creates \Imagick object from bitmap or vector file
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try {
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$bp = $this->getResizedPreview($tmpPath, $maxX, $maxY);
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} catch (\Exception $e) {
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\OC::$server->get(LoggerInterface::class)->info(
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'File: ' . $file->getPath() . ' Imagick says:',
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[
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'exception' => $e,
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'app' => 'core',
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]
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);
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return null;
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}
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$this->cleanTmpFiles();
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//new bitmap image object
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$image = new \OCP\Image();
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$image->loadFromData((string)$bp);
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//check if image object is valid
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return $image->valid() ? $image : null;
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}
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/**
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* Returns a preview of maxX times maxY dimensions in PNG format
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*
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* * The default resolution is already 72dpi, no need to change it for a bitmap output
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* * It's possible to have proper colour conversion using profileimage().
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* ICC profiles are here: http://www.color.org/srgbprofiles.xalter
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* * It's possible to Gamma-correct an image via gammaImage()
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*
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* @param string $tmpPath the location of the file to convert
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* @param int $maxX
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* @param int $maxY
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*
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* @return \Imagick
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*
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* @throws \Exception
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*/
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private function getResizedPreview($tmpPath, $maxX, $maxY) {
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$bp = new Imagick();
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// Validate mime type
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$bp->pingImage($tmpPath . '[0]');
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$mimeType = $bp->getImageMimeType();
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if (!preg_match($this->getAllowedMimeTypes(), $mimeType)) {
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throw new \Exception('File mime type does not match the preview provider: ' . $mimeType);
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}
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// Layer 0 contains either the bitmap or a flat representation of all vector layers
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$bp->readImage($tmpPath . '[0]');
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$bp = $this->resize($bp, $maxX, $maxY);
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$bp->setImageFormat('png');
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return $bp;
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}
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/**
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* Returns a resized \Imagick object
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*
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* If you want to know more on the various methods available to resize an
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* image, check out this link : @link https://stackoverflow.com/questions/8517304/what-the-difference-of-sample-resample-scale-resize-adaptive-resize-thumbnail-im
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*
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* @param \Imagick $bp
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* @param int $maxX
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* @param int $maxY
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*
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* @return \Imagick
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*/
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private function resize($bp, $maxX, $maxY) {
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[$previewWidth, $previewHeight] = array_values($bp->getImageGeometry());
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// We only need to resize a preview which doesn't fit in the maximum dimensions
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if ($previewWidth > $maxX || $previewHeight > $maxY) {
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// TODO: LANCZOS is the default filter, CATROM could bring similar results faster
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$bp->resizeImage($maxX, $maxY, imagick::FILTER_LANCZOS, 1, true);
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}
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return $bp;
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}
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}
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