FAL handling in FlexForms

flexform.xml

<settings.test>
	<TCEforms>
		<label>LLL:EXT:my_ext/Resources/Private/Language/locallang_db.xlf:flexform.my_ext.root.test</label>
		<config>
			<type>inline</type>
			<maxitems>1</maxitems>
			<foreign_table>sys_file_reference</foreign_table>
			<!--<foreign_field>uid_foreign</foreign_field>-->
			<foreign_table_field>tablenames</foreign_table_field>
			<foreign_label>uid_local</foreign_label>
			<foreign_sortby>sorting_foreign</foreign_sortby>
			<foreign_selector>uid_local</foreign_selector>
			<foreign_selector_fieldTcaOverride type="array">
				<config>
					<appearance>
						<elementBrowserType>file</elementBrowserType>
						<elementBrowserAllowed>jpg,png</elementBrowserAllowed>
					</appearance>
				</config>
			</foreign_selector_fieldTcaOverride>
			<foreign_match_fields type="array">
				<fieldname>image</fieldname>
			</foreign_match_fields>
			<appearance type="array">
				<newRecordLinkAddTitle>1</newRecordLinkAddTitle>
				<headerThumbnail>
					<field>uid_local</field>
					<height>64</height>
					<width>64</width>
				</headerThumbnail>
			</appearance>
		</config>
	</TCEforms>
</settings.test>

MyController.php

public function indexAction() {
	/** @var \TYPO3\CMS\Core\Resource\ResourceFactory $resourceFactory */
	$resourceFactory = GeneralUtility::makeInstance('TYPO3\\CMS\\Core\\Resource\\ResourceFactory');
	$fileReference = $resourceFactory->getFileReferenceObject($this->settings['test']);
	$fileArray = $fileReference->getProperties();
	$this->view->assign('image', $fileArray);
}

Teamplate.html

<f:image src="{image.uid}" treatIdAsReference="1" alt="{image.title}" maxWidth="200" />

For TYPO3 8.7.7 an update for Controller and Fluid template:

(Controller)

/** @var \TYPO3\CMS\Core\Resource\ResourceFactory $resourceFactory */
$resourceFactory = GeneralUtility::makeInstance('TYPO3\\CMS\\Core\\Resource\\ResourceFactory');
$fileReference = $resourceFactory->getFileReferenceObject($this->settings['test']);
$this->view->assign('image', $fileReference);

(Fluid template)

<f:image image="{image}" />