C#编程：创建直角坐标系的步骤解析

 string[] month = new string[12] { "一月", "二月", "三月", "四月", "五月", "六月", "七月", "八月", "九月", "十月", "十一月", "十二月" };
            float[] d = new float[12] { 20.5F, 60, 10.8F, 15.6F, 30, 70.9F, 50.3F, 30.7F, 70, 50.4F, 30.8F, 20 };
            //画图初始化    
            Bitmap bMap = new Bitmap(500, 500);
            Graphics gph = Graphics.FromImage(bMap);
            gph.Clear(Color.White);

            PointF cPt = new PointF(40, 420);//中心点    
            PointF[] xPt = new PointF[3]{
             new   PointF(cPt.Y+15,cPt.Y),
             new   PointF(cPt.Y,cPt.Y-8),
             new   PointF(cPt.Y,cPt.Y+8)};//X轴三角形    
            PointF[] yPt = new PointF[3]{
             new   PointF(cPt.X,cPt.X-15),
             new   PointF(cPt.X+8,cPt.X),
             new   PointF(cPt.X-8,cPt.X)};//Y轴三角形    
            gph.DrawString("某工厂某产品月生产量图表", new Font("宋体", 14),
             Brushes.Black, new PointF(cPt.X + 12, cPt.X));//图表标题    
            //画X轴    
            gph.DrawLine(Pens.Black, cPt.X, cPt.Y, cPt.Y, cPt.Y);
            gph.DrawPolygon(Pens.Black, xPt);
            gph.FillPolygon(new SolidBrush(Color.Black), xPt);
            gph.DrawString("月份", new Font("宋体", 12),
             Brushes.Black, new PointF(cPt.Y + 12, cPt.Y - 10));
            //画Y轴    
            gph.DrawLine(Pens.Black, cPt.X, cPt.Y, cPt.X, cPt.X);
            gph.DrawPolygon(Pens.Black, yPt);
            gph.FillPolygon(new SolidBrush(Color.Black), yPt);
            gph.DrawString("单位(万)", new Font("宋体", 12), Brushes.Black, new PointF(6, 7));
            for (int i = 1; i <= 12; i++)