title: Creating a simple black image with opencv using cvcreateimage
body: <p>Very basic question coming from a newbie in OpenCV. I just want to create an image with every pixel set to <code>0</code> (black). I have used the following code in the main() function:</p>
  
  <pre><code>IplImage* imgScribble = cvCreateImage(cvSize(320, 240), 8, 3);
  </code></pre>
  
  <p>And what I get is a solid gray image, instead of the black one.</p>
  
  <p>Thanks in advance !</p>