根据图片的链接获取图片的宽高

//根据图片的链接获取图片的宽高
- (CGSize)downloadImageSizeWithURL:(id)imageURL
{
    NSURL *URL = nil;
    if([imageURL isKindOfClass:[NSURL class]]){
        URL = imageURL;
    }
    if([imageURL isKindOfClass:[NSString class]]){
        URL = [NSURL URLWithString:imageURL];
    }
    if(URL == nil)
        return CGSizeZero;

#ifdef dispatch_main_sync_safe
    if([[SDImageCache sharedImageCache] diskImageExistsWithKey:absoluteString]){
        UIImage* image = [[SDImageCache sharedImageCache] imageFromMemoryCacheForKey:absoluteString];
        if(!image){
            NSData* data = [[SDImageCache sharedImageCache] performSelector:@selector(diskImageDataBySearchingAllPathsForKey:) withObject:URL.absoluteString];
            image = [UIImage imageWithData:data];
        }
        if(image){
            return image.size;
        }
    }
#endif

    CGSize size = CGSizeZero;
    NSMutableURLRequest *request = [[NSMutableURLRequest alloc] initWithURL:URL];
    NSString *pathExtendsion = [URL.pathExtension lowercaseString];

    if([pathExtendsion isEqualToString:@"png"]){
        size = [self downloadPNGImageSizeWithRequest:request];
    }else if([pathExtendsion isEqual:@"gif"]){
        size = [self downloadGIFImageSizeWithRequest:request];
    }else{
        size = [self downloadJPGImageSizeWithRequest:request];
    }

    if(CGSizeEqualToSize(CGSizeZero, size)){
        NSData* data = [NSURLConnection sendSynchronousRequest:[NSURLRequest requestWithURL:URL] returningResponse:nil error:nil];
        UIImage* image = [UIImage imageWithData:data];
        if(image){
#ifdef dispatch_main_sync_safe
            [[SDImageCache sharedImageCache] storeImage:image recalculateFromImage:YES imageData:data forKey:URL.absoluteString toDisk:YES];
#endif
            size = image.size;
        }
    }
    return size;
}

原帖地址：http://blog.csdn.net/li6185377/article/details/26225799