title: CGBitmapContextCreateImage on flipped context
body: <p>I've got a context, on which i've performed some drawing. Now i want to save a result. Because of inverted context y-axis first i want to flip everything, then create image:</p>
  
  <pre><code>// 1. Flip Y
  CGContextTranslateCTM(context, 0, height);
  CGContextScaleCTM(context, 1.0, -1.0);
  
  // 2. Create image
  CGImageRef rawMask = CGBitmapContextCreateImage(context);
  </code></pre>
  
  <p>However the image is not flipped. Even if i change the order of action 1 with 2, the image still is not flipped. I can't understand why and how to fix it. More important is 'why', because in my logic, if i flip the context with upside down drawing, it should be ok.</p>