title: Best way resize photo gallery for preview
body: <p>My app has more then 1000 photos and 50 galleries. It looks like as iphone Photos app. In preview list of gallery I have problem with performance. 
  In profile I saw what [sourceImage drawInRect:thumbnailRect] take 96% of time. 
  What is the best way to fix this issue?</p>
  
  <p>Duplicate with small size of images I did.
  Perhaps there is another solution?</p>