IOS-网络图片保存到本地（PNG和GIF）

1，获取图片类型
jpg 和 gif 的保存 方式不同。

//获取图片类型
    NSString * imageType = [self.slide_pic componentsSeparatedByString:@"."].lastObject;

2，下载图片

/**
 *  下载新图片，根据类型不同使用不同的保存方式
 */
- (void)downloadAdImageWithUrl:(NSString *)imageUrl imageName:(NSString *)imageName
{
    //保存 gif 类型
    __weak typeof(self) weakSelf = self;
    
    if([[_imageType lowercaseString] isEqualToString:@"gif"]){
        NSString *filePath = [self getFilePathWithImageName:imageName];
        NSURLSessionConfiguration *config = [NSURLSessionConfiguration defaultSessionConfiguration];
        NSURLSession *session = [NSURLSession sessionWithConfiguration:config];
        NSURL *url = [NSURL URLWithString:_imgUrl];
        
        
        NSURLSessionDownloadTask *task = [session downloadTaskWithURL:url completionHandler:^(NSURL * _Nullable location, NSURLResponse * _Nullable response, NSError * _Nullable error) {
                    if (error) {
                        NSLog(@"gif download error:%@", error);
                    } else {
                         NSLog(@"gif download success, file path:%@",location.path);
        //                这个方法下载的图片在 tmp 目录，移动到缓存目录下。
                        [self savaSuccess:imageName];
                        NSFileManager *manager = [NSFileManager defaultManager];
                        [manager moveItemAtPath:location.path toPath:filePath error:nil];
                     
                    }
                }];
        [task resume];

    }else if(_imageType != nil){
        dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{

            SDWebImageManager *sdimage = [[SDWebImageManager alloc]init];
            [sdimage loadImageWithURL:[NSURL URLWithString:imageUrl] options:SDWebImageRetryFailed context:nil progress:nil completed:^(UIImage * _Nullable image, NSData * _Nullable data, NSError * _Nullable error, SDImageCacheType cacheType, BOOL finished, NSURL * _Nullable imageURL) {
                __strong typeof(self) strongSelf = weakSelf;
                NSString *filePath = [self getFilePathWithImageName:imageName];
                if ([UIImagePNGRepresentation(image) writeToFile:filePath atomically:YES]) {
                    // 保存成功
                    [strongSelf savaSuccess:imageName];
                }else{
                    NSLog(@"保存失败");
                }
                
            }];
        });
    }
}
/// 保存图片后的操作
/// @param imageName  图片名
-(void)savaSuccess:(NSString *)imageName{
    NSLog(@"保存成功");
    //删除旧广告图片
    [self deleteOldImage];
    //设置新图片
    [UserDefaults setValue:imageName forKey:adImageName];
    //设置广告链接
    [UserDefaults setValue:_adUrl forKey:adUrl];
    [UserDefaults setValue:_adOpenType forKey:adOpen];
    [UserDefaults synchronize];
}

/**
 *  根据图片名拼接文件路径
 */
- (NSString *)getFilePathWithImageName:(NSString *)imageName
{

    if (imageName) {
        NSString *cachesPath = [NSSearchPathForDirectoriesInDomains(NSCachesDirectory,NSUserDomainMask, YES) firstObject];
        NSString *imgPath =[cachesPath stringByAppendingPathComponent:imageName];
        return imgPath;
    }
    return nil;
}


/**
 *  删除旧图片
 */
- (void)deleteOldImage
{
    NSString *imageName = [UserDefaults valueForKey:adImageName];
    if (imageName) {
        NSString *imgPath = [self getFilePathWithImageName:imageName];
        NSFileManager *fileManager = [NSFileManager defaultManager];
        [fileManager removeItemAtPath:imgPath error:nil];
    }
}

3，显示图片
sdwebimage 可以加载 gif 会动，imageview 直接加载 gif 不会动。

[_adView sd_setImageWithURL:[NSURL fileURLWithPath:_imgPath]];