C#Graphics 画图类操作

一、如何在桌面作图

1.引用

using System.Drawing;

using System.Runtime.InteropServices;

2.调用系统API

　　　　 [DllImport("user32.dll", CharSet = CharSet.Auto, ExactSpelling = true)]
        public static extern IntPtr GetDesktopWindow();
        [DllImport("user32.dll", EntryPoint = "GetDCEx", CharSet = CharSet.Auto, ExactSpelling = true)]
        private static extern IntPtr GetDCEx(IntPtr hWnd, IntPtr hrgnClip, int flags);

 3.初始化Graphics 类

            IntPtr desk = GetDesktopWindow();
            IntPtr deskDC = GetDCEx(desk, IntPtr.Zero, 0x403);
            Graphics g = Graphics.FromHdc(deskDC);

4.操作作图

            //Start point
            Point newPoint = new Point(0, 0);
            Pen p = new Pen(Color.Blue, 1);
            var Rectangle = new Rectangle(newPoint, new Size(500, 300));
            g.DrawRectangle(p, Rectangle);
            g.DrawString("测试", new Font("宋体", 50, FontStyle.Bold), Brushes.Red, new PointF(100, 100));