C#中利用GDI作圖解決異或問題

　　using System;

　　using SystemDrawing;

　　using SystemCollections;

　　using SystemComponentModel;

　　using SystemWindowsForms;

　　using SystemData;

　　using SystemRuntimeInteropServices;

　　namespace RubberBands

　　{

　　/// <summary>

　　/// Summary description for Form

　　/// </summary>

　　public class RubberBandForm : SystemWindowsFormsForm

　　{

　　/// API Declarations

　　private struct POINTAPI {

　　public int x;

　　public int y;

　　}

　　[DllImport(gdiDLL)]

　　private static extern Int SetROP(IntPtr hDC

　　int nDrawMode);

　　[DllImport(gdidll)]

　　private static extern bool MoveToEx(IntPtr hDC

　　int x

　　int y

　　POINTAPI lpPoint);

　　[DllImport(gdidll)]

　　private static extern bool LineTo(IntPtr hDC

　　int x

　　int y);

　　[DllImport(gdidll)]

　　private static extern IntPtr CreatePen(int nPenStyle

　　int nWidth

　　int crColor);

　　[DllImport(gdidll)]

　　private static extern IntPtr SelectObject(IntPtr hDC

　　IntPtr hObject);

　　[DllImport(gdidll)]

　　private static extern bool DeleteObject(IntPtr hObject);

　　private const int R_NOT = ;

　　private const int R_XORPEN = ;

　　private const int PS_DOT = ;

　　/// <summary>

　　/// Required designer variable

　　/// </summary>

　　private SystemComponentModelContainer components = null;

　　private SystemDrawingGraphics m_oDrawingSurface;

　　private POINTAPI m_ptsStart = new POINTAPI();

　　private POINTAPI m_ptsPrevious;

　　public RubberBandForm()

　　{

　　//

　　// Required for Windows Form Designer support

　　//

　　InitializeComponent();

　　//Add any initialization after the InitializeComponent() call

　　m_oDrawingSurface = thisCreateGraphics();

　　}

　　/// <summary>

　　/// Clean up any resources being used

　　/// </summary>

　　protected override void Dispose( bool disposing )

　　{

　　if( disposing )

　　{

　　if (components != null)

　　{

　　componentsDispose();

　　}

　　}

　　baseDispose( disposing );

　　}

　　protected override void OnMouseDown(MouseEventArgs e) {

　　// Check whether the left mouse button

　　// has generated the associated event

　　if (eButton == MouseButtonsLeft) {

　　// Store the starting point for your rubberband line

　　m_ptsStartx = eX;

　　m_ptsStarty = eY;

　　// Store the previous end point for your rubberband line

　　m_ptsPrevious = m_ptsStart;

　　}

　　baseOnMouseDown (e);

　　}

　　protected override void OnMouseMove(MouseEventArgs e) {

　　// Check if the left mouse button is pressed

　　if( eButton == MouseButtonsLeft) {

　　// Declare local variables

　　// handle to an appropriate device context obtained

　　// from m_oDrawingSurface

　　IntPtr hDC;

　　// previous mix mode; returned from SetROP

　　Int Mix ;

　　// temporary variables used for rubberbanding logic

　　POINTAPI ptsCurrent;

　　POINTAPI ptsOld = new POINTAPI();

　　// determines whether MoveToEx and LineTo calls are successful

　　Boolean Success;

　　// Store the current end point of your rubberband line

　　ptsCurrentx = eX;

　　ptsCurrenty = eY;

　　// Perform the requisite graphical operations

　　// Obtain a handle to an appropriate device context

　　hDC = m_oDrawingSurfaceGetHdc();

　　// Set the raster mode to invert the screen color

　　Mix = SetROP(hDC R_NOT);

　　// Move to the starting point of the rubberband line

　　Success = MoveToEx(hDC m_ptsStartx m_ptsStarty ptsOld);

　　// Erase the previous line

　　Success = LineTo(hDC m_ptsPreviousx m_ptsPreviousy);

　　// Move to the starting point of the rubberband line

　　Success = MoveToEx(hDC m_ptsStartx m_ptsStarty ptsOld);

　　// Draw the new line

　　Success = LineTo(hDC ptsCurrentx ptsCurrenty);

　　// Release the obtained handle to a device context

　　m_oDrawingSurfaceReleaseHdc(hDC);

　　// Store the current end point for the next erase operation

　　m_ptsPrevious = ptsCurrent;

　　}

　　baseOnMouseMove (e);

　　}

　　#region Windows Form Designer generated code

　　/// <summary>

　　/// Required method for Designer support do not modify

　　/// the contents of this method with the code editor

　　/// </summary>

　　private void InitializeComponent()

　　{

　　//

　　// RubberBandForm

　　//

　　thisAutoScaleBaseSize = new SystemDrawingSize( );

　　thisBackColor = SystemDrawingSystemColorsWindow;

　　thisClientSize = new SystemDrawingSize( );

　　thisName = RubberBandForm;

　　thisText = Using Unmanaged APIs;

　　}

　　#endregion

　　/// <summary>

　　/// The main entry point for the application

　　/// </summary>

　　[STAThread]

　　static void Main()

　　{

　　ApplicationRun(new RubberBandForm());

　　}

　　}

　　}

From:http://tw.wingwit.com/Article/program/ASP/201311/21870.html