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<?php
declare(strict_types=1);
/**
* SPDX-FileCopyrightText: 2024 Nextcloud GmbH and Nextcloud contributors
* SPDX-License-Identifier: AGPL-3.0-or-later
*/
namespace OC\Blurhash\Listener;
use GdImage;
use kornrunner\Blurhash\Blurhash;
use OC\Files\Node\File;
use OCP\EventDispatcher\Event;
use OCP\EventDispatcher\IEventDispatcher;
use OCP\EventDispatcher\IEventListener;
use OCP\Files\GenericFileException;
use OCP\Files\NotPermittedException;
use OCP\FilesMetadata\AMetadataEvent;
use OCP\FilesMetadata\Event\MetadataBackgroundEvent;
use OCP\FilesMetadata\Event\MetadataLiveEvent;
use OCP\IPreview;
use OCP\Lock\LockedException;
/**
* Generate a Blurhash string as metadata when image file is uploaded/edited.
*
* @template-implements IEventListener<AMetadataEvent>
*/
class GenerateBlurhashMetadata implements IEventListener {
private const COMPONENTS_X = 4;
private const COMPONENTS_Y = 3;
public function __construct(
private IPreview $preview,
) {
}
/**
* @throws NotPermittedException
* @throws GenericFileException
* @throws LockedException
*/
public function handle(Event $event): void {
if (!($event instanceof MetadataLiveEvent)
&& !($event instanceof MetadataBackgroundEvent)) {
return;
}
$file = $event->getNode();
if (!($file instanceof File)) {
return;
}
$currentEtag = $file->getEtag();
$metadata = $event->getMetadata();
if ($metadata->getEtag('blurhash') === $currentEtag) {
return;
}
// too heavy to run on the live thread, request a rerun as a background job
if ($event instanceof MetadataLiveEvent) {
$event->requestBackgroundJob();
return;
}
if (!str_starts_with($file->getMimetype(), 'image/')) {
return;
}
// Preview are disabled, so we skip generating the blurhash.
if (!$this->preview->isAvailable($file)) {
return;
}
$preview = $this->preview->getPreview($file, 64, 64, cacheResult: false);
$image = @imagecreatefromstring($preview->getContent());
if (!$image) {
return;
}
$metadata->setString('blurhash', $this->generateBlurHash($image))
->setEtag('blurhash', $currentEtag);
}
/**
* @param GdImage $image
*
* @return string
*/
public function generateBlurHash(GdImage $image): string {
$width = imagesx($image);
$height = imagesy($image);
$pixels = [];
for ($y = 0; $y < $height; ++$y) {
$row = [];
for ($x = 0; $x < $width; ++$x) {
$index = imagecolorat($image, $x, $y);
$colors = imagecolorsforindex($image, $index);
$row[] = [$colors['red'], $colors['green'], $colors['blue']];
}
$pixels[] = $row;
}
return Blurhash::encode($pixels, self::COMPONENTS_X, self::COMPONENTS_Y);
}
/**
* @param IEventDispatcher $eventDispatcher
*
* @return void
*/
public static function loadListeners(IEventDispatcher $eventDispatcher): void {
$eventDispatcher->addServiceListener(MetadataLiveEvent::class, self::class);
$eventDispatcher->addServiceListener(MetadataBackgroundEvent::class, self::class);
}
}
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