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:
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; }