 that generally images are protected by copyright law regardless whether they contain such invisible metadata or not.</p>
      </dd>
    </dl>
<h2>Tools</h2>
    <p data-role="slow-tools">Zopfli and PNGOUT are very good PNG compressors, but are very slow. Disable them if you need to optimize PNG files quickly (leave only AdvPNG for fastest, but still good compression).</p>
    <p data-role="dirty-alpha-tools">Zopfli and OptiPNG will clean RGB values of transparent pixels (known as “dirty alpha”). Disab