如何使用ImageFormatConverter.ConvertFromString包含HTML响应图像的字符串转换？ [英] How can I use ImageFormatConverter.ConvertFromString to convert a string containing HTML response to an image?

问题描述

这是什么实现，帮助请：

在页面加载

  {
    panelmain.Controls.Add（ABC）;
    panelmain.Controls.Add（GRID1）;
    串toexport;
    toexport = RenderControl（panelmain）;    ImageFormatConverter IMGC =新ImageFormatConverter（）;
    为System.Drawing.Image convertedimage;
    convertedimage =（System.Drawing.Image对象）imgc.ConvertFromString（toexport）;
    Response.ContentType =图像/ JPG
    Response.AppendHeader（内容处置，内联;文件名= tm.jpeg）;
    Response.BufferOutput =真;
    Response.Charset的=UTF-8;
    的Response.Write（convertedimage）;
    到Response.End（）;
    //form1.Controls.Add(abc）;
}公共字符串RenderControl（控制CTRL）
{
    StringBuilder的SB =新的StringBuilder（）;
    StringWriter的TW =新的StringWriter（某人）;
    HtmlTextWriter的HW =新的HtmlTextWriter（TW）;
    ctrl.RenderControl（HW）;
    回复于（某人）;
    返回sb.ToString（）;
}
 

该错误是：

  

ImageFormatConverter不能从System.String转换。

解决方案

您可能misinter preTED的文档 ConvertFromString 在这里，解释：

您使用的是 ImageformatConverter 类，它继承并重写 的TypeConverter 。这意味着 ConvertFromString 从超类继承的，但因为没有办法，你可以将字符串转换为图像（除非你有一个生动的想象力），此方法始终返回null （根据文档），或抛出一个引发NotSupportedException 。这是基类的默认行为和压倒一切的类可以定义自定义的行为，而你的情况，的尚未完成。

要从一个字符串，你首先必须定义你想要的转换。即，是字符串图像的路径？它是一段文字，并要渲染从一个图像？它是一个Base64编码的连接包含图像codeD字符串？它是一个呈现的HTML页面或它包含的RTF文档？一旦你有了这些问题的答案，就可以选择正确的转换器或图像构造。

编辑：因为你的问题似乎是有关呈现HTML作为一个图像，请这个职位在SO ，也是由 rchern上面提到

This is what achieved, help please:

in pageload

{
    panelmain.Controls.Add(abc);
    panelmain.Controls.Add(grid1);
    string toexport;
    toexport = RenderControl(panelmain);

    ImageFormatConverter imgc = new ImageFormatConverter();
    System.Drawing.Image convertedimage;
    convertedimage = (System.Drawing.Image) imgc.ConvertFromString(toexport);
    Response.ContentType = "image/jpg";
    Response.AppendHeader("Content-Disposition", "inline;filename=tm.jpeg");
    Response.BufferOutput = true;
    Response.Charset = "utf-8";
    Response.Write(convertedimage);
    Response.End();
    //form1.Controls.Add(abc);
}

public string RenderControl(Control ctrl)
{
    StringBuilder sb = new StringBuilder();
    StringWriter tw = new StringWriter(sb);
    HtmlTextWriter hw = new HtmlTextWriter(tw);
    ctrl.RenderControl(hw);
    Response.Write(sb);
    return sb.ToString();
}

The error is:

ImageFormatConverter cannot convert from System.String.

解决方案

You may have misinterpreted the documentation of ConvertFromString here, explanation:

You are using an ImageformatConverter class which inherits and overrides TypeConverter. This means that ConvertFromString is inherited from the superclass, but because there's no way you can convert a string to an image (unless you have a vivid imagination), this method always returns null (according to documentation), or throws a NotSupportedException. This is the default behavior of the base class and an overriding class can define custom behavior, which in your case, has not been done.

To convert from a string you will first have to define what you want. I.e., is the string a path to an image? Is it a piece of text and you want to render an image from that? Is it a Base64 encoded string that contains an image? Is it a rendered HTML page or does it contain an RTF document? Once you have an answer to these questions, you can choose the correct converter or image constructor.

EDIT: because your question seems to be about rendering HTML as an image, check out this post at SO, as also mentioned by rchern above.

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