title: How to get depth data from depth image?
body: <p>everyone!
  I have an depth image, now i want to get depth data from this image, so i use following codes:</p>
  <pre><code>//Read an depth image sample01.jpg
  Mat img = imread(&quot;D:\\2d-3d\\sample01.jpg&quot;);
  System.out.println(img);
  </code></pre>
  <p>But i get following result:</p>
  <pre><code>org.bytedeco.opencv.opencv_core.Mat[width=1536,height=2048,depth=8,channels=3]
  </code></pre>
  <p>Why is it just 3-channel data? Instead of a 4-channel one? How can I get the depth data on the fourth channel?</p>