title: QImage/QPixmap size limitations?
body: <p>Are there any known size/space limitation of <code>QPixmap</code> and/or <code>QImage</code> objects documented? I did not find any useful information regarding this. I'm currently using Qt 4.7.3 on OSX and Windows. Particulary I'm interested in:</p>
  
  <ul>
  <li>Width/Height limits?</li>
  <li>Limits depending on color format?</li>
  <li>Difference between 32/64 bit machines?</li>
  <li>Difference regarding OS?</li>
  </ul>
  
  <p>I would naively suspect that memory is the only limitation, so one could calculate max size by </p>
  
  <blockquote>
    <p>width x height x byte_per_pixel</p>
  </blockquote>
  
  <p>I assume that there is a more elaborate rule of thumb; also 32 bit machines may have addressing problems when you run into GB dimensions.</p>
  
  <p>In the end I want to store multiple RGBA images of about 16000x16000 pixel in size and render them using transparency onto each other within a <code>QGraphicsScene</code>. The workstation available can have a lot of RAM, let's say 16GB.</p>
  
  <p><strong>tl;dr: What size limits of QImage/QPixmap are you aware of, or where can I find such information?</strong></p>
  
  <p><strong>Edit:</strong> I'm aware of the tiling approach and I'm fine with that. Still it would be great to know the things described above.</p>
  
  <p>Thanks!</p>