title: iOS: ImageIO resizing on a rectangular image
body: <p>I'm trying to create thumbnails of images for my app. I'm using <em>CGImageSourceCreateThumbnailAtIndex</em> to do it. One problem I'm seeing is that for the options, <em>kCGImageSourceThumbnailMaxPixelSize</em> is the max pixel size for both width and height.</p>
  
  <p>The problem I'm having is: I have an image that is 500w x 1000h and I want to scale it down to say 250w x 500h. When I use <em>CGImageSourceCreateThumbnailAtIndex</em> I want to specify the width to be 250 but instead it seems to be making my height 250 instead.</p>
  
  <p>How can I use this to scale down a rectangular image by width?</p>
  
  <p>Thanks!</p>