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