保存图片到沙盒

+ (void)saveImagePermanent:(UIImage *)currentImage withName:(NSString *)imageName{

    //高保真压缩图片可可将图片压缩，但图片质量基本保持不变，第二个参数即图片高保真参数。

    NSData *imageData=UIImageJPEGRepresentation(currentImage, 0.3);

     NSFileManager *fileManager = [[NSFileManager alloc] init];

     NSString *createPath=[[NSSearchPathForDirectoriesInDomains(NSDocumentDirectory,       NSUserDomainMask, YES) lastObject] stringByAppendingPathComponent:@"filePath"];

    NSString *fullPath=[createPath stringByAppendingPathComponent:imageName];

    // 判断文件夹是否存在，若是不存在，则建立

    if (![[NSFileManager defaultManager] fileExistsAtPath:createPath]) {

        [fileManager createDirectoryAtPath:createPath withIntermediateDirectories:YES attributes:nil error:nil];

    } else { 

        NSLog(@"FileDir is exists.");

    }

    //图片写入文件

    [imageData writeToFile:fullPath atomically:NO];

}