Issue with loading and caching retina images for UIImageView animation

问题:

What I have

For my game I'm creating several animations using view.animationImages = imagesArray; [view startAnimating];

In my animation helper class I use this

- (UIImage *)loadRetinaImageIfAvailable:(NSString *)path {     NSString *retinaPath = [[path stringByDeletingLastPathComponent] stringByAppendingPathComponent:[NSString stringWithFormat:@"%@@2x.%@", [[path lastPathComponent] stringByDeletingPathExtension], [path pathExtension]]];      if ([UIScreen mainScreen].scale == 2.0 && [[NSFileManager defaultManager] fileExistsAtPath:retinaPath] == YES)         return [[UIImage alloc] initWithCGImage:[[UIImage imageWithData:[NSData dataWithContentsOfFile:retinaPath]] CGImage] scale:2.0 orientation:UIImageOrientationUp];     else         return [UIImage imageWithContentsOfFile:path]; }  - (NSMutableArray *)generateCachedImageArrayWithFilename:(NSString *)filename extension:(NSString *)extension andImageCount:(int)count {     _imagesArray = [[NSMutableArray alloc] init];     _fileExtension = extension;     _imageName = filename;     _imageCount = count;      for (int i = 0; i < count; i++)     {         NSString *tempImageNames = [NSString stringWithFormat:@"%@%i", filename, i];         NSString *imagePath = [[NSBundle mainBundle] pathForResource:tempImageNames ofType:extension];          UIImage *frameImage = [self loadRetinaImageIfAvailable:imagePath];         UIGraphicsBeginImageContext(frameImage.size);         CGRect rect = CGRectMake(0, 0, frameImage.size.width, frameImage.size.height);         [frameImage drawInRect:rect];         UIImage *renderedImage = UIGraphicsGetImageFromCurrentImageContext();         UIGraphicsEndImageContext();          [_imagesArray addObject:renderedImage];          if (_isDoublingFrames)         {             [_imagesArray addObject:renderedImage];         }         else if (_isTriplingFrames)         {             [_imagesArray addObject:renderedImage];             [_imagesArray addObject:renderedImage];         }          NSLog(@"filename = %@", filename);     }      return _imagesArray; } 

Problem and facts

• Without caching images I got retina versions of images byt my animations are not fluent
• If I cache images this way, animations are ok, but uses non-retina versions of images

Please is there some other way to cache and get retina versions?

回答1:

Are these images located in your application bundle? If so this logic is all unnecessary because the imageWithContentsOfFile: method will already detect and load the @2x image on a retina device.

Also, you'd be better off using the [UIImage imageNamed:] method instead because this automatically caches the image for re-use, and decompresses it immediately, avoiding the need for manually caching the images, or for that trickery with drawing it into an offscreen CGContext.

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