Question

I have some images I need to get from the web. Just using data from a URL.
They need to show correctly on Retina Display.
When I get the images from the web, they still look pixelated. I need to set the images’ scale to retina display (2.0), but I must be missing something.
Here’s what I did so far.

UIImage *img = [UIImage imageWithData:[NSData dataWithContentsOfURL:@"http://www.msdomains.com/tmp/test.png"];

CGRect labelFrame = CGRectMake(0,0,64,64);
UIImageView *imageView = [[UIImageView alloc] initWithFrame:labelFrame];
imageView.contentScaleFactor = [UIScreen mainScreen].scale;

[imageView setImage:img];
[self addSubview:imageView];
[imageView release];

Answer 1

Your code should work pretty much as-is. I don’t know what the original dimensions of your image were, but I’d guess they were 64×64 px. In order to scale down correctly, the original image would need to be 128×128 px.

As a test, the following code correctly displayed my photo in Retina resolution on the Simulator, and on my iPhone 4:

UIImage *img = [UIImage imageWithData:[NSData dataWithContentsOfURL:[NSURL URLWithString:@"http://www.seenobjects.org/images/mediumlarge/2006-08-19-native-lilac.jpg"]]];

CGRect labelFrame = CGRectMake(0, 0, 375, 249.5);
UIImageView *imageView = [[UIImageView alloc] initWithFrame:labelFrame];

[imageView setImage:img];
[self.view addSubview:imageView];

Note that the UIImageView is 375×249.5 points, which is half of the original (pixel) dimensions of the photo. Also, setting the contentScaleFactor didn’t seem to be necessary.

(As an aside, I can’t see that specifying @2x on the URL will help, in this case, as the call to dataWithContentsOfURL: will return an opaque blob of data, with no trace of the filename left. It’s that opaque data that’s then passed to imageWithData: to load the image.)