SDWebImage download image

                    /**
                     *  SDWebImage download images
                     */
                    SDWebImageDownloader *downloader = [SDWebImageDownloader sharedDownloader];
                    [downloader downloadImageWithURL:[NSURL URLWithString:[dic objectForKey:@"pic_url"]]
                                             options:0
                                            progress:^(NSInteger receivedSize, NSInteger expectedSize) {
                                                // progression tracking code
                                            }
                                           completed:^(UIImage *image, NSData *data, NSError *error, BOOL finished) {
                                               if (image && finished) {
                                                   
                                                   /**
                                                    *  将路径作为key
                                                    */
                                                   NSString *cacheImageKey = [[SDWebImageManager sharedManager] cacheKeyForURL:[NSURL URLWithString:[dic objectForKey:@"pic_url"]]];
                                                   
                                                   /**
                                                    *  通过路径的key获取沙盒图片的路径
                                                    */
                                                   NSString *cacheImagePath = [[SDImageCache sharedImageCache] defaultCachePathForKey:cacheImageKey];
                                                   
                                                   /**
                                                    *  拿到缓存到本地的图片
                                                    */
                                                   UIImage *normalImage = [[UIImage alloc]initWithContentsOfFile:cacheImagePath];
                                                   
                                                   /**
                                                    *  将UIImage转成@2x的尺寸大小
                                                    */
                                                   normalImage = [UIImage imageWithCGImage:normalImage.CGImage scale:2 orientation:normalImage.imageOrientation];
                                                   
                                                   
                                                   homeItem.image = [normalImage imageWithRenderingMode:UIImageRenderingModeAlwaysOriginal];
                                                   homeItem.selectedImage = [normalImage imageWithRenderingMode:UIImageRenderingModeAlwaysOriginal];
                                                   homeVC.tabBarItem = homeItem;
                                                   
                                                   NSLog(@"cacheImagePath:%@",cacheImagePath);
                                                   
                                                   // do something with image
                                               }
                                           }];
                    
                    /**
                     *  图片下载方法
                     */
                    [imageNormal sd_setImageWithURL:[NSURL URLWithString:[dic objectForKey:@"pic_url"]] completed:^(UIImage *image, NSError *error, SDImageCacheType cacheType, NSURL *imageURL) {
                        if (image) {
                            
                            imageNormal.frame = CGRectMake(0, 0, image.size.width/2, image.size.height/2);
                            homeItem.image = [imageNormal.image imageWithRenderingMode:UIImageRenderingModeAlwaysOriginal];
                            homeVC.tabBarItem = homeItem;
                        }
                    }];