title: Copy part of scaled UIImage
body: <p>I want to be able to scale and position an image, and then save just part of that image. I currently have a UIImageView inside a UIScrollView. After zooming and positioning the image I hit a button and then have the following code.</p>
  
  <pre><code>// imageScale = current scale of UIView
  // get the new width and height of the scaled UIView
  float scaledImageWidth = [scrollView viewWithTag:1].frame.size.width;
  float scaledImageHeight = [scrollView viewWithTag:1].frame.size.height;
  
  // get starting X and Y coords of target in relation to UIView 
  // target is a box in the middle of the screen, 210x255px
  float imageY = scaledImageHeight / 2 - (scrollView.contentOffset.y * imageScale);
  imageY = (imageY &lt; 0) ? (140 * imageScale) + ((imageY * -1) + (scrollView.contentOffset.y *imageScale)) : (140 * imageScale) - imageY;
  
  float imageX = scaledImageWidth / 2 - (scrollView.contentOffset.x * imageScale);
  imageX = (imageX &lt; 0) ? (56 * imageScale) + ((imageX * -1) + (scrollView.contentOffset.x *imageScale)) : (56 * imageScale) - imageX;
  
  // image = original unscaled UIImage
  // create new UIImage that matches the size of the scaled UIView we have been working with
  UIGraphicsBeginImageContext( CGSizeMake(scaledImageWidth, scaledImageHeight) );
  [image drawInRect:CGRectMake(0,0,scaledImageWidth, scaledImageHeight)];
  UIImage* newImage = UIGraphicsGetImageFromCurrentImageContext();
  UIGraphicsEndImageContext();
  
  // now with the UIImage that is the size we want, copy a piece of the image 
  CGImageRef imageRef = CGImageCreateWithImageInRect([newImage CGImage], CGRectMake(imageX,imageY,210, 255));
  UIImage* myThumbnail = [UIImage imageWithCGImage:imageRef];
  CGImageRelease(imageRef);
  </code></pre>
  
  <p>This seems to work mostly ok. The problem I see is that when I make the final copy of just a piece of the image, the copy (myThumbnail) isn't scaled. However, the source (newImage) appears to scale without problems. Does anyone know what I am missing, or if there would be a different approach to this problem?</p>
  
  <p><strong>Edit:</strong>
  Ok, I was a little off. The copy is scaling. The problem I'm having is its position is off. So if the image position is too far in one direction, the new copy wont be in the right position. For example, if I move the image so that I'm cropping the bottom left, it might give me a sliver on the right instead of that bottom left portion of the image.</p>