ext_localconf.php

<?php

$configuration = unserialize($GLOBALS['TYPO3_CONF_VARS']['EXT']['extConf']['imageoptimizer']);

if (!isset($signalSlotDispatcher)) {
	$signalSlotDispatcher = \TYPO3\CMS\Core\Utility\GeneralUtility::makeInstance('TYPO3\CMS\Extbase\SignalSlot\Dispatcher');
}

if ((isset($configuration['jpgOnUpload']) && (bool)$configuration['jpgOnUpload'] === TRUE) ||
	(isset($configuration['pngOnUpload']) && (bool)$configuration['pngOnUpload'] === TRUE) ||
	(isset($configuration['gifOnUpload']) && (bool)$configuration['gifOnUpload'] === TRUE) ||
	(isset($configuration['svgOnUpload']) && (bool)$configuration['svgOnUpload'] === TRUE)) {
	$signalSlotDispatcher->connect(
		'TYPO3\\CMS\\Core\\Resource\\ResourceStorage',
		\TYPO3\CMS\Core\Resource\ResourceStorage::SIGNAL_PreFileAdd,
		'Lemming\\Imageoptimizer\\FileAspects',
		'addFile'
	);

	$signalSlotDispatcher->connect(
		'TYPO3\\CMS\\Core\\Resource\\ResourceStorage',
		\TYPO3\CMS\Core\Resource\ResourceStorage::SIGNAL_PreFileReplace,
		'Lemming\\Imageoptimizer\\FileAspects',
		'replaceFile'
	);
}

if ((isset($configuration['jpgOnProcessing']) && (bool)$configuration['jpgOnProcessing'] === TRUE) ||
	(isset($configuration['pngOnProcessing']) && (bool)$configuration['pngOnProcessing'] === TRUE) ||
	(isset($configuration['gifOnProcessing']) && (bool)$configuration['gifOnProcessing'] === TRUE)) {
	$signalSlotDispatcher->connect(
		'TYPO3\\CMS\\Core\\Resource\\ResourceStorage',
		\TYPO3\CMS\Core\Resource\Service\FileProcessingService::SIGNAL_PostFileProcess,
		'Lemming\\Imageoptimizer\\FileAspects',
		'processFile'
	);
}

if (TYPO3_MODE === 'BE') {
	$GLOBALS['TYPO3_CONF_VARS']['SC_OPTIONS']['reports']['tx_reports']['status']['providers']['ImageOptimizer'][] =
		\Lemming\Imageoptimizer\StatusReport::class;
}