GDI+画圆角矩形

GraphicsPath* MakeRoundRect(Point topLeft, Point bottomRight, INT percentageRounded)
{
	ASSERT (percentageRounded >= 1 && percentageRounded <= 100);

	INT left  = min(topLeft.X, bottomRight.X);
	INT right = max(topLeft.X, bottomRight.X);

	INT top    = min(topLeft.Y, bottomRight.Y);
	INT bottom = max(topLeft.Y, bottomRight.Y);

	INT offsetX = (right-left)*percentageRounded/100;  
	INT offsetY = (bottom-top)*percentageRounded/100;

	GraphicsPath pt;
	GraphicsPath * path = pt.Clone();

	path->AddArc(right-offsetX, top, offsetX, offsetY, 270, 90);
	path->AddArc(right-offsetX, bottom-offsetY, offsetX, offsetY, 0, 90);
	path->AddArc(left, bottom - offsetY, offsetX, offsetY, 90, 90);
	path->AddArc(left, top, offsetX, offsetY, 180, 90);
	path->AddLine(left + offsetX, top, right - offsetX/2, top);
	return path;
}

原文： http://www.vckbase.com/document/viewdoc/?id=1428