📄 “流”的利用--网络传输屏幕图像.htm
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width=593><FONT color=#306830> 建议分辨率:800X600</FONT></TD></TR>
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<p align=center>谈Delphi编程中“流”的利用--网络传输屏幕图像</p>
<p align=center>陈经韬</p>
五、实际应用之四：利用流实现网络传输屏幕图像<BR>
<BR>
大家应该见过很多网管程序，这类程序其中有一个功能就是监控远程电脑的屏幕。实际上，这也是利用流操作来实现的。下面我们给出一个例子，这个例子分两个程序，一个服务端，一个是客户端。程序编译后可以直接在单机、局部网或者互联网上使用。程序中已经给出相应注释。后面我们再来作具体分析。<BR>
新建一个工程，在Internet面版上拖一个ServerSocket控件到窗口，该控件主要用于监听客户端，用来与客户端建立连接和通讯。设置好监听端口后调用方法Open或者Active:=True即开始工作。注意：跟前面的NMUDP不同，当Socket开始监听后就不能再改变它的端口，要改变的话必须先调用Close或设置Active为False，否则将会产生异常。另外，如果该端口已经打开的话，就不能再用这个端口了。所以程序运行尚未退出就不能再运行这个程序，否则也会产生异常，即弹出出错窗口。实际应用中可以通过判断程序是否已经运行，如果已经运行就退出的方法来避免出错。<BR>
当客户端有数据传入，将触发ServerSocket1ClientRead事件，我们可以在这里对接收的数据进行处理。在本程序中，主要是接收客户端发送过来的字符信息并根据事先的约定来进行相应操作。<BR>程序全部代码如下：<BR><BR>unit
Unit1;{服务端程序}<BR>interface<BR>uses<BR>Windows, Messages, SysUtils,
Classes, Graphics, Controls, Forms, Dialogs, JPEG,ExtCtrls,
ScktComp;<BR>type<BR>TForm1 = class(TForm)<BR>ServerSocket1:
TServerSocket;<BR>procedure ServerSocket1ClientRead(Sender:
TObject;Socket: TCustomWinSocket);<BR>procedure FormCreate(Sender:
TObject);<BR>procedure FormClose(Sender: TObject; var Action:
TCloseAction);<BR>private<BR>procedure Cjt_GetScreen(var Mybmp: TBitmap;
DrawCur: Boolean);<BR>{自定义抓屏函数,DrawCur表示抓鼠标图像与否}<BR>{ Private declarations
}<BR>public<BR>{ Public declarations }<BR>end;<BR>var<BR>Form1:
TForm1;<BR>MyStream: TMemorystream;{内存流对象} <BR>implementation<BR>{$R
*.DFM}<BR>procedure TForm1.Cjt_GetScreen(var Mybmp: TBitmap; DrawCur:
Boolean);<BR>var<BR>Cursorx, Cursory: integer;<BR>dc: hdc;<BR>Mycan:
Tcanvas;<BR>R: TRect;<BR>DrawPos: TPoint;<BR>MyCursor: TIcon;<BR>hld:
hwnd;<BR>Threadld: dword;<BR>mp: tpoint;<BR>pIconInfo:
TIconInfo;<BR>begin<BR>Mybmp := Tbitmap.Create; {建立BMPMAP }<BR>Mycan :=
TCanvas.Create; {屏幕截取}<BR>dc := GetWindowDC(0);<BR>try<BR>Mycan.Handle :=
dc;<BR>R := Rect(0, 0, screen.Width, screen.Height);<BR>Mybmp.Width :=
R.Right;<BR>Mybmp.Height := R.Bottom;<BR>Mybmp.Canvas.CopyRect(R, Mycan,
R);<BR>finally<BR>releaseDC(0, DC);<BR>end;<BR>Mycan.Handle :=
0;<BR>Mycan.Free;<BR>if DrawCur then
{画上鼠标图象}<BR>begin<BR>GetCursorPos(DrawPos);<BR>MyCursor :=
TIcon.Create;<BR>getcursorpos(mp);<BR>hld :=
WindowFromPoint(mp);<BR>Threadld := GetWindowThreadProcessId(hld,
nil);<BR>AttachThreadInput(GetCurrentThreadId, Threadld,
True);<BR>MyCursor.Handle :=
Getcursor();<BR>AttachThreadInput(GetCurrentThreadId, threadld,
False);<BR>GetIconInfo(Mycursor.Handle, pIconInfo);<BR>cursorx :=
DrawPos.x - round(pIconInfo.xHotspot);<BR>cursory := DrawPos.y -
round(pIconInfo.yHotspot);<BR>Mybmp.Canvas.Draw(cursorx, cursory,
MyCursor); {画上鼠标}<BR>Mycursor.ReleaseHandle; {释放数组内存}<BR>MyCursor.Free;
{释放鼠标指针}<BR>end; <BR>end;<BR>procedure TForm1.FormCreate(Sender:
TObject);<BR>begin<BR>ServerSocket1.Port := 3000;
{端口}<BR>ServerSocket1.Open; {Socket开始侦听}<BR>end;<BR>procedure
TForm1.FormClose(Sender: TObject; var Action:
TCloseAction);<BR>begin<BR>if ServerSocket1.Active then
ServerSocket1.Close; {关闭Socket}<BR>end;<BR>procedure
TForm1.ServerSocket1ClientRead(Sender: TObject;<BR>Socket:
TCustomWinSocket);<BR>var<BR>S, S1: string;<BR>MyBmp: TBitmap;<BR>Myjpg:
TJpegimage;<BR>begin<BR>S := Socket.ReceiveText;<BR>if S = 'cap' then
{客户端发出抓屏幕指令}<BR>begin<BR>try<BR>MyStream :=
TMemorystream.Create;{建立内存流}<BR>MyBmp := TBitmap.Create;<BR>Myjpg :=
TJpegimage.Create;<BR>Cjt_GetScreen(MyBmp, True);
{True表示抓鼠标图像}<BR>Myjpg.Assign(MyBmp);
{将BMP图象转成JPG格式,便于在互联网上传输}<BR>Myjpg.CompressionQuality := 10;
{JPG文件压缩百分比设置,数字越大图像月清晰,但数据也越大}<BR>Myjpg.SaveToStream(MyStream);
{将JPG图象写入流中}<BR>Myjpg.free;<BR>MyStream.Position := 0;{注意:必须添加此句}<BR>s1 :=
inttostr(MyStream.size);{流的大小}<BR>Socket.sendtext(s1);
{发送流大小}<BR>finally<BR>MyBmp.free;<BR>end;<BR>end;<BR>if s = 'ready' then
{客户端已准备好接收图象}<BR>begin<BR>MyStream.Position :=
0;<BR>Socket.SendStream(MyStream);
{将流发送出去}<BR>end;<BR>end;<BR>end.<BR><BR>
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