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>