magento-test/app/code/Magento/MediaGalleryRenditions/etc/adminhtml/system.xml

<?xml version="1.0"?>
<!--
/**
 * Copyright © Magento, Inc. All rights reserved.
 * See COPYING.txt for license details.
 */
-->
<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:module:Magento_Config:etc/system_file.xsd">
    <system>
        <section id="system">
            <group id="media_gallery_renditions" translate="label" type="text" sortOrder="1010" showInDefault="1" showInWebsite="0" showInStore="0">
                <label>Media Gallery Image Optimization</label>
                <field id="enabled" translate="label" type="select" sortOrder="10" showInDefault="1" showInWebsite="0" showInStore="0">
                    <label>Enable Image Optimization</label>
                    <source_model>Magento\Config\Model\Config\Source\Yesno</source_model>
                </field>
                <comment>Resize images to improve performance and decrease the file size. When you use an image from Media Gallery on the storefront, the smaller image is generated and placed instead of the original.
                    Changing these settings will update all generated images.</comment>
                <field id="width" translate="label" type="text" sortOrder="20" showInDefault="1" showInWebsite="0" showInStore="0">
                    <label>Maximum Width</label>
                    <validate>validate-zero-or-greater validate-digits</validate>
                    <comment>Enter the maximum width of an image in pixels.</comment>
                </field>
                <field id="height" translate="label" type="text" sortOrder="30" showInDefault="1" showInWebsite="0" showInStore="0">
                    <label>Maximum Height</label>
                    <validate>validate-zero-or-greater validate-digits</validate>
                    <comment>Enter the maximum height of an image in pixels.</comment>
                </field>
            </group>
        </section>
    </system>
</config>