Loading UIImages automatically in high-resolution works fine for locally stored images – but if you want to fetch them via remote URL you have to code yourself.
A simple, blocking but backward compatible (iOS >= 3.0, maybe even 2.0 but untested) implementation could look like this:
1@implementation UIImage (MRORemote)
2
3// add the @2x filename suffix
4+(NSURL *)url2x:(NSURL *)url
5{
6 NSString *path = url.path;
7 NSAssert(path != nil, @"");
8 NSString *last = path.lastPathComponent;
9 NSString *ext = path.pathExtension;
10 NSAssert(last != nil, @"");
11 NSAssert(ext != nil, @"");
12 NSString *part = [last substringToIndex:MAX(0, last.length - ext.length - 1)];
13 return [NSURL URLWithString:[NSString stringWithFormat:@"%@@2x.%@", part, ext] relativeToURL:[url absoluteURL]];
14}
15
16+(UIImage *)imageWithContentsOfURL:(NSURL *)url probe2x:(BOOL)probe2x
17{
18 if ( url == nil )
19 return nil;
20 UIScreen *screen = [UIScreen mainScreen];
21 const CGFloat scale = [screen respondsToSelector:@selector(scale)] ? [screen scale] : 1.0f;
22 if ( probe2x && 2.0f == scale && [UIImage respondsToSelector:@selector(imageWithCGImage:scale:orientation:)] ) {
23 UIImage *img = nil;
24 NSData *raw = [NSData dataWithContentsOfURL:[UIImage url2x:url]];
25 if ( raw != nil )
26 img = [UIImage imageWithData:raw];
27 if ( img != nil )
28 img = [UIImage imageWithCGImage:img.CGImage scale:scale orientation:img.imageOrientation];
29 if ( img != nil )
30 return img;
31 NSAssert(raw == nil && img == nil, @"");
32 }
33 // MRLogD(@"loading %@", [url absoluteURL]);
34 NSData *raw = [NSData dataWithContentsOfURL:url];
35 if ( raw == nil )
36 return nil;
37 return [UIImage imageWithData:raw];
38}
39@endUse at your will but without any warranty.
