Image Chooser for Magento2 widgets

ImageChooser.php

<?php
namespace Vendor\Module\Block\Adminhtml\Widget;

class ImageChooser extends \Magento\Backend\Block\Template
{
    /**
     * @var \Magento\Framework\Data\Form\Element\Factory
     */
    protected $_elementFactory;

    /**
     * @param \Magento\Backend\Block\Template\Context $context
     * @param \Magento\Framework\Data\Form\Element\Factory $elementFactory
     * @param array $data
     */
    public function __construct(
        \Magento\Backend\Block\Template\Context $context,
        \Magento\Framework\Data\Form\Element\Factory $elementFactory,
        array $data = []
    ) {
        $this->_elementFactory = $elementFactory;
        parent::__construct($context, $data);
    }

    /**
     * Prepare chooser element HTML
     *
     * @param \Magento\Framework\Data\Form\Element\AbstractElement $element Form Element
     * @return \Magento\Framework\Data\Form\Element\AbstractElement
     */
    public function prepareElementHtml(\Magento\Framework\Data\Form\Element\AbstractElement $element)
    {
        $config = $this->_getData('config');
        $sourceUrl = $this->getUrl('cms/wysiwyg_images/index',
            ['target_element_id' => $element->getId(), 'type' => 'file']);
        $chooser = $this->getLayout()->createBlock('Magento\Backend\Block\Widget\Button')
            ->setType('button')
            ->setClass('btn-chooser')
            ->setLabel($config['button']['open'])
            ->setOnClick('MediabrowserUtility.openDialog(\''. $sourceUrl .'\')')
            ->setDisabled($element->getReadonly());

        $input = $this->_elementFactory->create("text", ['data' => $element->getData()]);
        $input->setId($element->getId());
        $input->setForm($element->getForm());
        $input->setClass("widget-option input-text admin__control-text");
        if ($element->getRequired()) {
            $input->addClass('required-entry');
        }

        $element->setData('after_element_html', $input->getElementHtml() . $chooser->toHtml());
        return $element;
    }
}

widget.xml

<?xml version="1.0" encoding="UTF-8"?>
<widgets xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:noNamespaceSchemaLocation="urn:magento:module:Magento_Widget:etc/widget.xsd">
    <widget id="my_new_custom_widget" class="Magento\Framework\View\Element\Template">
        <label translate="true">My new custom widget</label>
        <description translate="true">My new custom widget description</description>
        <parameters>
            <parameter name="image" xsi:type="block" required="true" visible="true" sort_order="10">
                <label translate="true">Background image</label>
                <block class="Vendor\Module\Block\Adminhtml\Widget\ImageChooser">
                    <data>
                        <item name="button" xsi:type="array">
                            <item name="open" xsi:type="string">Choose Image...</item>
                        </item>
                    </data>
                </block>
            </parameter>
        </parameters>
    </widget>
</widgets>

Hi,
thank you guys for all your hints. I just tried the solution on Magento 2.4.2 and it works. I slightly modified the code, I removed the constructor because it says that the class \Magento\Backend\Helper\Data is deprecated. So here's my version

<?php

declare(strict_types=1);

namespace VENDOR\PACKAGE\Model;

use Magento\Widget\Model\Widget as MagentoWidget;

class Widget
{
    public function beforeGetWidgetDeclaration(
        MagentoWidget $subject,
        $type,
        $params = [],
        $asIs = true
    ): array
    {
        foreach ($params as $name => $value) {
            if (preg_match('/(___directive\/)([a-zA-Z0-9,_-]+)/', $value, $matches)) {
                $directive = base64_decode(strtr($matches[2], '-_,', '+/='));
                $params[$name] = str_replace(['{{media url="', '"}}'], ['', ''], $directive);
            }
        }

        return [$type, $params, $asIs];
    }
}

Hi Guys,
I was looking for a solution for ___directive issue and finally found the following simple way to fix the issue for Magento 2.3.5 and newer.
In the ImageChooser class, it is necessary to add the following line to the text input element definition:

$input->addCustomAttribute('data-force_static_path', 1);

That will force the Media Browser to generate static links related to the website root (starting from /media).