参数在Image中无效

Question

我想从不同的网址获取屏幕截图。对于此任务，我使用System.Net.WebRequest和System.Net.WebResponse并获取System.IO.StreamReader

但是按照以下代码给出错误：

System.Drawing.Image img = System.Drawing.Image.FromStream(ms);

  

参数无效。   

System.Drawing.Image.FromStream（Stream stream，Boolean useEmbeddedColorManagement，Boolean validateImageData）+397      System.Drawing.Image.FromStream（Stream stream）+9      E：\ Prectices \ WebApplication10 \ WebApplication10 \ WebForm1.aspx.cs中的WebApplication10.WebForm1.ConvertHtmlToImage（）：124      E：\ Prectices \ WebApplication10 \ WebApplication10 \ WebForm1.aspx.cs中的WebApplication10.WebForm1.Button1_Click（Object sender，EventArgs e）：104      System.Web.UI.WebControls.Button.OnClick（EventArgs e）+109      System.Web.UI.WebControls.Button.RaisePostBackEvent（String eventArgument）+109      System.Web.UI.WebControls.Button.System.Web.UI.IPostBackEventHandler.RaisePostBackEvent（String eventArgument）+10      System.Web.UI.Page.RaisePostBackEvent（IPostBackEventHandler sourceControl，String eventArgument）+13      System.Web.UI.Page.RaisePostBackEvent（NameValueCollection postData）+31      System.Web.UI.Page.ProcessRequestMain（Boolean includeStagesBeforeAsyncPoint，Boolean includeStagesAfterAsyncPoint）+3466

我的代码如下：

string content = "";
            string url = "http://www.contoso.com/PostAccepter.aspx";
            System.Net.WebRequest webRequest = WebRequest.Create(url);
            System.Net.WebResponse webResponse = webRequest.GetResponse();
            System.IO.StreamReader sr = new StreamReader(webResponse.GetResponseStream(), System.Text.Encoding.GetEncoding("UTF-8"));
            content = sr.ReadToEnd();
            //save to file
            //byte[] b = Convert.FromBase64String(content);
            byte[] b = Encoding.UTF8.GetBytes(content);
            System.IO.MemoryStream ms = new System.IO.MemoryStream(b);
            System.Drawing.Image img = System.Drawing.Image.FromStream(ms);
            img.Save(@"E:\Test1.png\image.png", System.Drawing.Imaging.ImageFormat.Jpeg);

            img.Dispose();
            ms.Close();