在 .NET、c# 中绘制形状的形状线问题

我想画一个有正方形、菱形和十字形的形状。方线实心细腻。但是，菱形和十字形的线条看起来像虚线或虚线。我希望所有形状都有实线。

有什么想法吗？

下面是代码和形状：

http://www.sendspace.com/file/n3wljs

private void CreateVariousShapes()
{
    Bitmap bitmap = new Bitmap(17, 17);
    Graphics graphics = Graphics.FromImage(bitmap);
    Pen pen = new Pen(Color.Black);
    pen.Width = 1;
    pen.DashStyle = DashStyle.Solid;
    Brush brush = new SolidBrush(Color.White);
    //graphics.FillRectangle(brush, 0, 0, 16, 16);
    //graphics.DrawRectangle(pen, 0, 0, 16, 16);
    FillDiamond(brush, graphics);
    DrawDiamond(pen, graphics);
    DrawCross(pen, graphics);
    //bitmap.Save(MapPath("SquareDiamondCross.png"),ImageFormat.Png);
    //bitmap.Save(MapPath("SquareCross.png"), ImageFormat.Png);
    //bitmap.Save(MapPath("SquareDiamond.png"), ImageFormat.Png);
    bitmap.Save(MapPath("DiamondCross.png"), ImageFormat.Png);
}
private void FillDiamond(Brush brush, Graphics graphics)
{
    Point[] points = new Point[]
                        { new Point(0,8), 
                        new Point(8,16), 
                        new Point(16,8), 
                        new Point(8,0), 
                        };
    graphics.FillPolygon(brush, points);
}
private void DrawDiamond(Pen pen, Graphics graphics)
{
    Point[] points = new Point[]
                        { new Point(0,8), 
                        new Point(8,16), 
                        new Point(16,8), 
                        new Point(8,0), 
                        };
    graphics.DrawPolygon(pen, points);
}
private void DrawCross(Pen pen, Graphics graphics)
{
    graphics.DrawLine(pen, 4, 2, 2, 4);
    graphics.DrawLine(pen, 2, 12, 4, 14);
    graphics.DrawLine(pen, 12, 14, 14, 12);
    graphics.DrawLine(pen, 12, 2, 14, 4);
    graphics.DrawLine(pen, 2, 4, 6, 8);
    graphics.DrawLine(pen, 2, 12, 6, 8);
    graphics.DrawLine(pen, 4, 14, 8, 10);
    graphics.DrawLine(pen, 12, 14, 8, 10);
    graphics.DrawLine(pen, 14, 12, 10, 8);
    graphics.DrawLine(pen, 14, 4, 10, 8);
    graphics.DrawLine(pen, 12, 2, 8, 6);
    graphics.DrawLine(pen, 4, 2, 8, 6);
}

graphics.InterpolationMode = InterpolationMode.HighQualityBicubic;
graphics.SmoothingMode = SmoothingMode.HighQuality;