iOS开发中，获取图片之后保存或下载到本地相册中

#pragma mark 先获取本地图片或者网络图片
- (void)saveHeaderImageWith:(NSString *)path
{
    UIImage *img = [UIImage imageWithContentsOfFile:path];
    //这里img也可以是从网络获取的图片
    [self saveImageToPhotos:img];
}

#pragma mark 保存图片
- (void)saveImageToPhotos:(UIImage*)savedImage
{
    UIImageWriteToSavedPhotosAlbum(savedImage, self, @selector(image:didFinishSavingWithError:contextInfo:), NULL);
}

#pragma mark 系统的完成保存图片的方法
- (void)image: (UIImage *) image didFinishSavingWithError: (NSError *) error contextInfo: (void *) contextInfo
{
    NSString *msg = nil ;
    if (error != NULL) {
        msg = @"保存图片失败" ;
    } else {
        msg = @"保存图片成功" ;
    }
    UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"保存图片结果提示" message:msg delegate:self cancelButtonTitle:@"确定" otherButtonTitles:nil];
    [alert show];
}