用 GDI+ 画 Chord

来源：互联网发布：求三唑仑淘宝上输什么编辑：程序博客网时间：2024/05/23 02:19

GDI+并没有提供GDI中的Chord函数（其它的还有RoundRect函数，可参考BobPowell 的这篇文章），只好自己动手了：

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BOOL GDIplusChord(HDC hDC,INT x1,INT y1,INT x2,INT y2,INT x3,INT y3,INT x4,INT y4 )
{
    Graphics graphics(hDC);
    CRect rectBound(x1, y1, x2, y2);
    rectBound.NormalizeRect();
    Rect ellipseRect(rectBound.left, rectBound.top, rectBound.Width(), rectBound.Height());
 
    ////////////////////////////////////////////////////////////////////////////////
    // For testing only.
    BYTE        byAlpha = 200;
    SolidBrush  fillBrush(Color(byAlpha, 0, 0, 255));
    Pen         redPen(Color(byAlpha, 255, 0, 0), 3);
    ////////////////////////////////////////////////////////////////////////////////
    Status ret = InvalidParameter;
 
    if ( x3 == x4 && y3 == y4 )
    {
        // If the starting point and ending point of the curve are the same, a complete ellipse should be drawn.
        ret = graphics.FillEllipse(&fillBrush, ellipseRect);
        ret = graphics.DrawEllipse(&redPen, ellipseRect);
        return Gdiplus::Ok == ret;
    }
 
    CPoint ptCenter(rectBound.CenterPoint());
 
#define PI 3.1415926
 
    REAL startAngle = atan2(y3-ptCenter.y, x3-ptCenter.x ) * 180.0f / PI;
    REAL sweepAngle = (atan2(y4-ptCenter.y, x4-ptCenter.x ) * 180.0f / PI) - startAngle - 360.0f;
    if ( sweepAngle < -360.0f )
        sweepAngle += 360.0f;
     
    GraphicsPath path;
    path.StartFigure();
    path.AddArc(ellipseRect, startAngle, sweepAngle);
    path.CloseFigure();
 
    ret = graphics.FillPath(&fillBrush, &path);
    ret = graphics.DrawPath(&redPen, &path);
     
    return Gdiplus::Ok == ret;
}

转自：http://www.cnblogs.com/yonken/archive/2010/05/06/Implement_Chord_Function_Using_GDIplus.html