如何调用Api画图

[luke91]

如何调用Api函数直接在窗体上画图？

[duan17]

/// API Declarations
private struct POINTAPI {
public int x;
public int y;
}

[DllImport("gdi32.DLL")]
private static extern Int32 SetROP2(IntPtr hDC,
int nDrawMode);

[DllImport("gdi32.dll")]
private static extern bool MoveToEx(IntPtr hDC,
int x,
int y,
POINTAPI lpPoint);

[DllImport("gdi32.dll")]
private static extern bool LineTo(IntPtr hDC,
int x,
int y);

[DllImport("gdi32.dll")]
private static extern IntPtr CreatePen(int nPenStyle,
int nWidth,
int crColor);

[DllImport("gdi32.dll")]
private static extern IntPtr SelectObject(IntPtr hDC,
IntPtr hObject);

[DllImport("gdi32.dll")]
private static extern bool DeleteObject(IntPtr hObject);

private const int R2_NOT = 6;
private const int R2_XORPEN = 7;

private const int PS_DOT = 2;

/// <summary>
/// Required designer variable.
/// </summary>
private System.ComponentModel.Container components = null;
private System.Drawing.Graphics 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 = this.CreateGraphics();

}

/// <summary>
/// Clean up any resources being used.
/// </summary>
protected override void Dispose( bool disposing )
{
if( disposing )
{
if (components != null)
{
components.Dispose();
}
}
base.Dispose( disposing );
}

protected override void OnMouseDown(MouseEventArgs e) {
// Check whether the left mouse button
// has generated the associated event.
if (e.Button == MouseButtons.Left) {
// Store the starting point for your rubber-band line.
m_ptsStart.x = e.X;
m_ptsStart.y = e.Y;
// Store the previous end point for your rubber-band line.
m_ptsPrevious = m_ptsStart;
}

base.OnMouseDown (e);
}

protected override void OnMouseMove(MouseEventArgs e) {
// Check if the left mouse button is pressed.

if( e.Button == MouseButtons.Left) {
// Declare local variables.
// handle to an appropriate device context obtained
// from m_oDrawingSurface
IntPtr hDC;
// previous mix mode; returned from SetROP2
Int32 Mix ;
// temporary variables used for rubber-banding logic
POINTAPI ptsCurrent;
POINTAPI ptsOld = new POINTAPI();
// determines whether MoveToEx and LineTo calls are successful
Boolean Success;

// Store the current end point of your rubber-band line.
ptsCurrent.x = e.X;
ptsCurrent.y = e.Y;

// Perform the requisite graphical operations.
// Obtain a handle to an appropriate device context
hDC = m_oDrawingSurface.GetHdc();
// Set the raster mode to invert the screen color
Mix = SetROP2(hDC, R2_NOT);
// Move to the starting point of the rubber-band line
Success = MoveToEx(hDC, m_ptsStart.x, m_ptsStart.y, ptsOld);
// Erase the previous line
Success = LineTo(hDC, m_ptsPrevious.x, m_ptsPrevious.y);
// Move to the starting point of the rubber-band line
Success = MoveToEx(hDC, m_ptsStart.x, m_ptsStart.y, ptsOld);
// Draw the new line
Success = LineTo(hDC, ptsCurrent.x, ptsCurrent.y);
// Release the obtained handle to a device context
m_oDrawingSurface.ReleaseHdc(hDC);

// Store the current end point for the next erase operation
m_ptsPrevious = ptsCurrent;
}

base.OnMouseMove (e);
}