title: PNG image is getting corrupted in Itext7
body: <pre><code>import static com.itextpdf.kernel.xmp.XMPUtils.decodeBase64;
  import com.itextpdf.io.image.ImageData;
  import com.itextpdf.io.image.ImageDataFactory;
  
  public  void testPngImage() throws XMPException {
      String orignalImage =  https://gist.github.com/nil96/d9d54200e5329211d2d7455492716500;
      String base64Image = orignalImage.replaceFirst("data:image/png;base64,","");
      byte[] decodedBytes = decodeBase64(base64Image);
      ImageData imageData = ImageDataFactory.create(decodedBytes,true);
      imageData.getData();
  }
  </code></pre>
  
  <p>when I print <code>imageData.getData()</code> I get byte array containing -1 only. Whereas expected png byte array should start with <code>{-119, 80, 78, 71}</code>. This is only happening for PNG images. I can create jpeg images successfully. I have attached png in gist <a href="https://gist.github.com/nil96/d9d54200e5329211d2d7455492716500" rel="nofollow noreferrer">https://gist.github.com/nil96/d9d54200e5329211d2d7455492716500</a></p>
  
  <p>Am I missing something for initializing Image or is it a bug?</p>
  
  <p>Dependency</p>
  
  <pre class="lang-xml prettyprint-override"><code>&lt;dependency&gt;
      &lt;groupId&gt;com.itextpdf&lt;/groupId&gt;
      &lt;artifactId&gt;itext7-core&lt;/artifactId&gt;
      &lt;version&gt;7.0.7&lt;/version&gt;
      &lt;!--&lt;version&gt;7.1.8&lt;/version&gt;--&gt;
      &lt;type&gt;pom&lt;/type&gt;
  &lt;/dependency&gt;
  </code></pre>