Question

How could I load a picture from a resource on a background thread?

I am currently doing this and it slows things quite a bit on my UI:

image = [NSData dataWithContentsOfFile:imageName];

I would rather it load it on a background thread.

Answer 1

dispatch_queue_t backgroundQueue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);
dispatch_queue_t mainQueue = dispatch_get_main_queue();
dispatch_async(backgroundQueue,^{
  // background process
  image = [NSData dataWithContentsOfFile:imageName];
  dispatch_async(mainQueue,^{
    // always update GUI from the main thread
    // uiimageview.image = image.... etc
 });
});