C#编写ActiveX网页截图控件

故事背景：Java组的小伙伴需要一个能在IE（还是6。。。）下截图并返回给网页的功能，但是IE做起来很麻烦（可能根本做不到），于是找到我写一个ActiveX控件实现此功能，想着可能还有其他小伙伴需要这个功能，于是就PO出来，供需要的人使用，当然也可以作为学习C#编写ActiveX的一个简单入门教程（VC++效果更好）。
功能截图如下：

代码分为两个核心部分：1、C#屏幕截图；2、C#开发ActivX控件。
 1、屏幕截图，这个在网上找到了一个只需要5行代码的实现（超级精简），当然你也可以费点功夫实现自由区域截取图片，截图后保存到本地，然后使用二进制读取jpg文件，并编码为base64返回给网页

 public string PrintScreen()
    {
      Image baseImage = new Bitmap(Screen.PrimaryScreen.Bounds.Width, Screen.PrimaryScreen.Bounds.Height);
      Graphics g = Graphics.FromImage(baseImage);
      g.CopyFromScreen(new Point(0, 0), new Point(0, 0), Screen.AllScreens[0].Bounds.Size);
      g.Dispose();
      baseImage.Save("D:\\screen.jpg", ImageFormat.Jpeg);
      Stream file = new FileStream("D:\\screen.jpg", FileMode.Open);
      BinaryReader bw = new BinaryReader(file);
      var buffer = new byte[file.Length];
      bw.Read(buffer, 0, buffer.Length);
      bw.Close();
      string b64 = Convert.ToBase64String(buffer);
      return b64;
    }

2、c#开发ActiveX控件，网上示例比较多
先新建一个类库，并设置项目属性，COM可见

并为COM互注册，这样编译完了会自动注册COM控件

完成设置后，编写代码，如下：

using System;
using System.Collections.Generic;
using System.Text;
using System.Runtime.InteropServices;

namespace PrintScreenLib
{
 //为了让ActiveX控件获得客户端的信任，控件类需要实现一个名为“IObjectSafety”的接口。先创建该接口（注意，不能修改该接口的GUID值）
 [ComImport, Guid("CB5BDC81-93C1-11CF-8F20-00805F2CD064")]
 [InterfaceType(ComInterfaceType.InterfaceIsIUnknown)]
 public interface IObjectSafety
 {
 [PreserveSig]
 int GetInterfaceSafetyOptions(ref Guid riid, [MarshalAs(UnmanagedType.U4)] ref int pdwSupportedOptions, [MarshalAs(UnmanagedType.U4)] ref int pdwEnabledOptions);

 [PreserveSig()]
 int SetInterfaceSafetyOptions(ref Guid riid, [MarshalAs(UnmanagedType.U4)] int dwOptionSetMask, [MarshalAs(UnmanagedType.U4)] int dwEnabledOptions);
 }
}

新建用户控件，并派生IObjectSafe接口，接口实现是固定内容

 [Guid("61D7F413-A1B2-48A9-B851-5BFBCF50280C")] //使用VS工具里的GUID生成器生成唯一码
 public partial class PSLib : UserControl, IObjectSafety
 {
 #region IObjectSafety 成员
 private const string _IID_IDispatch = "{00020400-0000-0000-C000-000000000046}";
 private const string _IID_IDispatchEx = "{a6ef9860-c720-11d0-9337-00a0c90dcaa9}";
 private const string _IID_IPersistStorage = "{0000010A-0000-0000-C000-000000000046}";
 private const string _IID_IPersistStream = "{00000109-0000-0000-C000-000000000046}";
 private const string _IID_IPersistPropertyBag = "{37D84F60-42CB-11CE-8135-00AA004BB851}";

 private const int INTERFACESAFE_FOR_UNTRUSTED_CALLER = 0x00000001;
 private const int INTERFACESAFE_FOR_UNTRUSTED_DATA = 0x00000002;
 private const int S_OK = 0;
 private const int E_FAIL = unchecked((int)0x80004005);
 private const int E_NOINTERFACE = unchecked((int)0x80004002);

 private bool _fSafeForScripting = true;
 private bool _fSafeForInitializing = true;

 public int GetInterfaceSafetyOptions(ref Guid riid, ref int pdwSupportedOptions, ref int pdwEnabledOptions)
 {
  int Rslt = E_FAIL;

  string strGUID = riid.ToString("B");
  pdwSupportedOptions = INTERFACESAFE_FOR_UNTRUSTED_CALLER | INTERFACESAFE_FOR_UNTRUSTED_DATA;
  switch (strGUID)
  {
  case _IID_IDispatch:
  case _IID_IDispatchEx:
   Rslt = S_OK;
   pdwEnabledOptions = 0;
   if (_fSafeForScripting == true)
   pdwEnabledOptions = INTERFACESAFE_FOR_UNTRUSTED_CALLER;
   break;
  case _IID_IPersistStorage:
  case _IID_IPersistStream:
  case _IID_IPersistPropertyBag:
   Rslt = S_OK;
   pdwEnabledOptions = 0;
   if (_fSafeForInitializing == true)
   pdwEnabledOptions = INTERFACESAFE_FOR_UNTRUSTED_DATA;
   break;
  default:
   Rslt = E_NOINTERFACE;
   break;
  }

  return Rslt;
 }

 public int SetInterfaceSafetyOptions(ref Guid riid, int dwOptionSetMask, int dwEnabledOptions)
 {
  int Rslt = E_FAIL;

  string strGUID = riid.ToString("B");
  switch (strGUID)
  {
  case _IID_IDispatch:
  case _IID_IDispatchEx:
   if (((dwEnabledOptions & dwOptionSetMask) == INTERFACESAFE_FOR_UNTRUSTED_CALLER) &&
    (_fSafeForScripting == true))
   Rslt = S_OK;
   break;
  case _IID_IPersistStorage:
  case _IID_IPersistStream:
  case _IID_IPersistPropertyBag:
   if (((dwEnabledOptions & dwOptionSetMask) == INTERFACESAFE_FOR_UNTRUSTED_DATA) &&
    (_fSafeForInitializing == true))
   Rslt = S_OK;
   break;
  default:
   Rslt = E_NOINTERFACE;
   break;
  }

  return Rslt;
 }
 #endregion

IE调用ActiveX控件：

<!DOCTYPE html>
<html>
 <head>
 <title>测试</title>

 <meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
 <meta http-equiv="description" content="this is my page">
 <meta http-equiv="content-type" content="text/html; charset=UTF-8">
 <script>
 function jt(){
  var str="";
  try
  {
  var obj = document.getElementById("MyActiveX");
   str=obj.PrintScreen();
  }
  catch(e)
  {
  alert(e);
  return;
  }

  var img=document.getElementById("img");
  img.src="data:image/jpeg;base64,"+str;//接受base64编码后的图片
 }
 </script>
 </head>

 <body>
 <OBJECT ID="MyActiveX" WIDTH="120" HEIGHT=20" CLASSID="CLSID:61D7F413-A1B2-48A9-B851-5BFBCF50280C"></OBJECT>
 <input type="button" value="截图" onclick="jt();">
 <Image id ="img" />
 </body>
</html>

一个完整的ActvieX控件就完成了，这里没有使用到事件，如果使用事件的话会更加麻烦一点。

下载：屏幕截图ActivX控件

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