从在线图像计算 MD5 哈希

Question

我需要计算一张在线图片的MD5散列值

对于本地保存的图像，我尝试了这段代码，它按预期工作：

public static string GetHashFromFile(string fileName, HashAlgorithm algorithm)
{
    HashAlgorithm MD5 = new MD5CryptoServiceProvider();
    using (var stream = new BufferedStream(File.OpenRead(fileName), 100000))
    {
        return BitConverter.ToString(MD5.ComputeHash(stream)).Replace("-", string.Empty);
    }
}

如何获取在线文件的BufferedStream？

Answer 1

使用 WebClient class to download the data from a given address. Use the downloaded bytes array to create a MemoryStream object to be the source stream of the BufferedStream 对象。

您有两种下载方式：

1.同步方式

static string GetHashFromUrl(string url)
{
    using (var wc = new WebClient())
    {
        var bytes = wc.DownloadData(url);

        using (var md5 = new MD5CryptoServiceProvider())
        using (var ms = new MemoryStream(bytes))
        using (var bs = new BufferedStream(ms, 100_000))
            return BitConverter.ToString(md5.ComputeHash(bs)).Replace("-", string.Empty);
    }
}

...和来电者：

void TheCaller()
{
    try
    {
        var hash = GetHashFromUrl(url);
        //...
    }
    catch (Exception ex)
    {
        MessageBox.Show(ex.Message);
    }            
}

2。异步方式

static async Task<string> GetHashFromUrlAsync(string url)
{
    using (var wc = new WebClient())
    using (var md5 = new MD5CryptoServiceProvider())
    {
        byte[] bytes = await wc.DownloadDataTaskAsync(url);
                
        using (var ms = new MemoryStream(bytes))
        using (var bs = new BufferedStream(ms, 100_000))
            return BitConverter.ToString(md5.ComputeHash(bs)).Replace("-", string.Empty);
    }
}

...和一个 async 来电者：

async void TheCaller()
{
    try
    {
        var hash = await Task.Run(() => GetHashFromUrlAsync(url));
        //...
    }
    catch (Exception ex)
    {
        MessageBox.Show(ex.Message);
    }            
}

两个函数 return this 照片的 FA544EB95534BA35AE9D6EA0B3889934 散列，它的地址分配给调用方的 url 变量。

从在线图像计算 MD5 哈希

Calculate the MD5 hash from an online image

c#

url

buffer

md5

image