title: text color in div with filter brightness background
body: <p>i have child div text problem.
  here is code.</p>
  
  <pre><code>&lt;div style="background-image:url(http://imgnews.naver.net/image/001/2014/07/01/PAP20140701204901034_P2_99_20140701204206.jpg); background-repeat:no-repeat; background-size:    cover; filter:brightness(0.7); -webkit-filter:brightness(0.7);"&gt;
  
       &lt;div&gt;
           &lt;h2&gt;this is text.&lt;/h2&gt;                      
       &lt;/div&gt;
  
  &lt;/div&gt;
  </code></pre>
  
  <p>and this is code output image with filter:brightness.</p>
  
  <p><img src="https://i.stack.imgur.com/f0Q8q.png" alt="enter image description here"></p>
  
  <p>but i want this.</p>
  
  <p><img src="https://i.stack.imgur.com/elnmn.png" alt="enter image description here"></p>
  
  <p>how can i fix this problem?</p>
  
  <p>how can childnode text be white with filter:brightness?</p>