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，这里就不啰嗦了
转载大萝卜控博客