title: Rotate image retaining center?
body: <p>I have this sample image</p>
  
  <p><img src="https://i.stack.imgur.com/tBJZX.png" alt="enter image description here"></p>
  
  <p>i need to block the center in the middle of the circle when i rotate.<br>
  What's the anchor point? It's the anchor point the problem?  </p>
  
  <p>Now the image rotate, unconsidering the anchor point.</p>
  
  <pre><code>_Image.layer.anchorPoint = CGPointMake(0.5, 0.5); //?
  [...]
  CGFloat wAngle = Degrees2Radians([_Weight.text intValue]/300.0*360);
  _Image.layer.transform = CATransform3DMakeRotation (wAngle+M_PI, 0, 0, 1);
  </code></pre>
  
  <p>I need to make a test, like an inverse clockwise starting from 0 to 300, retaining the center.</p>
  
  <blockquote>
    <p>0, arrow to bottom<br>
    150, arrow to top<br>
    300, arrow to bottom<br>
    etc...</p>
  </blockquote>
  
  <p>thanks.</p>