Fast image loading code that can be used in a background thread. Essentially forces the image to be decompressed right away, not on the fly. Uses ImageIO framework.

UIImage+Decompressed.m

@implementation UIImage (Decompressed)
+ (UIImage *)decompressedImageWithContentsOfFile:(NSString *)path
{
    NSDictionary *dict = @{(id)kCGImageSourceShouldCache : @(YES)};
    
    NSData * data = [NSData dataWithContentsOfFile:path];
    
    if (data == nil) {
        return nil;
    }
    
    CGImageSourceRef source = CGImageSourceCreateWithData((__bridge CFDataRef)data, NULL);
    
    if (source == NULL) {
        return nil;
    }
    
    CGImageRef cgImage = CGImageSourceCreateImageAtIndex(source, 0, (__bridge CFDictionaryRef)dict);
    
    CFRelease(source);
    
    CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
    
    CGContextRef context = CGBitmapContextCreate(NULL,
                                                 CGImageGetWidth(cgImage),
                                                 CGImageGetHeight(cgImage),
                                                 8,
                                                 CGImageGetWidth(cgImage) * 4,
                                                 colorSpace,
                                                 // makes system not need to do extra conversion when displayed
                                                 kCGImageAlphaPremultipliedFirst | kCGBitmapByteOrder32Little);
    CGColorSpaceRelease(colorSpace);
    
    if (!context) {
        CGImageRelease(cgImage);
        return nil;
    }
    
    CGRect rect = (CGRect){CGPointZero, {CGImageGetWidth(cgImage), CGImageGetHeight(cgImage)}};
    CGContextDrawImage(context, rect, cgImage);
    CGImageRef decompressedImageRef = CGBitmapContextCreateImage(context);
    CGContextRelease(context);
    
    CGImageRelease(cgImage);
    
    UIImage *decompressedImage = [UIImage imageWithCGImage:decompressedImageRef scale:[UIScreen mainScreen].scale orientation:UIImageOrientationUp];
    CGImageRelease(decompressedImageRef);
    return decompressedImage;
}
@end