:orphan:

=====================================================
Legacy: thumbnails via headless.php (ImageViewHelper)
=====================================================

    Status: **SUPERSEDED by declarative image variants** — for File fields of a Content Block, replace this pattern with `headless.yaml <../Howto/DefineImageVariants.rst>`__. Kept as the historical reference for migrating existing blocks; production sites carry many copies of this file (13 on the site this extension was built for). One case is **not** yet replaceable: images inside Collection items — see the `migration guide <../Howto/MigrateLegacyThumbnails.rst>`__.

The pattern
===========

`your_extension/ContentBlocks/ContentElements/your-content-block-element/headless.php` with thumbnail generation through the Fluid `ImageViewHelper`:

..  code-block:: php

    <?php

    use TYPO3\CMS\Fluid\ViewHelpers\Uri\ImageViewHelper;

    $generateThumbnail = function (array $arguments): string {
        if (array_key_exists('absolute', $arguments) === false) {
            $arguments['absolute'] = true;
        }

        $imageViewHelper = new ImageViewHelper();

        foreach ($imageViewHelper->prepareArguments() as $argumentKey => $argumentDefinition) {
            if (array_key_exists($argumentKey, $arguments) === false) {
                $arguments[$argumentKey] = $argumentDefinition->getDefaultValue();
            }
        }

        $imageViewHelper->setArguments($arguments);

        return $imageViewHelper->initializeArgumentsAndRender();

    };

    foreach ($data['items'] ?? [] as $itemKey => $item) {

        if ($item['image']) {
            $image = $item['image'];

            $data['items'][$itemKey]['image']['thumbnails'] = [
                'mobile' => $generateThumbnail(['src' => $image['id'], 'treatIdAsReference' => true, 'width' => 320]),
                'desktop' => $generateThumbnail(['src' => $image['id'], 'treatIdAsReference' => true, 'width' => 800]),
            ];
        }
    }

    return $data;

Why it was replaced
===================

*   Every Content Block repeated the same generator with different widths — pure duplication across site packages.
*   Driving a Fluid ViewHelper from PHP for URL generation is an abuse of the ViewHelper API (no DI, awkward argument filling, hidden dependencies).
*   Nothing about the variants was declarative or reviewable — widths hid in PHP closures.

The declarative replacement produces the same `thumbnails` map next to the frozen `id/alt/title/publicUrl` shape: `Define image variants <../Howto/DefineImageVariants.rst>`__.