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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