Create an image with a specific cropping variant in a TYPO3 user function or similar

cropVariantsInUserFunction.php

<?php

$contentObjectRenderer = \TYPO3\CMS\Core\Utility\GeneralUtility::makeInstance(\TYPO3\CMS\Frontend\ContentObject\ContentObjectRenderer::class);
$filesContent = \TYPO3\CMS\Core\Utility\GeneralUtility::makeInstance(\TYPO3\CMS\Frontend\ContentObject\FilesContentObject::class,
    $contentObjectRenderer);
$filesConfiguration = [
    'references' => '50', // this is a UID from sys_file_reference
    'renderObj' => 'IMAGE',
    'renderObj.' => [
        'file' => '50', // this is the same UID as above
        'file.' => [
            'treatIdAsReference' => true,
            'width' => '265c',
            'height' => '143c',
            'crop.' => [
                'data' => 'file:current:crop'
            ],
            'cropVariant' => 'xs' // the name of the crop variant
        ]
    ]
];
$imageTag = $filesContent->render($filesConfiguration);
echo $imageTag;

Works fine up to TYPO3 v11.
Breaks with v12. The problem is that I don't have a valid content object in my request, since I'm running the process as a user func.
If this is in extbase context where you initialize the process through a plugin, it probably also works fine in v12.

In my case, this solution works in v12 without initializing a frontend request:

$contentObjectRenderer = GeneralUtility::makeInstance(ContentObjectRenderer::class);
$imgResourceConf = [
    'file' => $publicUrl,   // file path or a file UID
    'file.' => [
        'treatIdAsReference' => true,
        'width' => $width,
        'height' => $height,
    ]
];
$url = $contentObjectRenderer->cObjGetSingle('IMG_RESOURCE', $imgResourceConf);