C# 在屏幕上画图效果的经典例子

C#实现在屏幕上画图的效果。

 

//DllImport所在的名字空间

using System.Runtime.InteropServices;

[DllImport("User32.dll")]

public extern static System.IntPtr GetDC(System.IntPtr hWnd);

private void button19_Click(object sender, EventArgs e)

{

System.IntPtr DesktopHandle = GetDC(System.IntPtr.Zero);

Graphics g = Graphics.FromHdc(DesktopHandle);

g.DrawRectangle(new Pen(Color.Red),new Rectangle(10,10,100,100));

}

附，c#画图的经典小例子

1.位图上绘制点和线

 

System.Drawing.Image MyImage=new System.Drawing.Bitmap (w,h)；//申请位图对象

System.Drawing.Graphics g=System.Drawing.Graphics.FromImage(MyImage); //申请画图对象

//用白色C清出除

Color C=Color.FromArgb(255,255,255);

g.Clear(C);

  

//画线

g.DrawLine(Pens.Black,x1,y1,x2,y2);

//画一个象素的点

//MyBitmap.SetPixel(x, y, Color.White);

g.DrawImage(MyImage,0,0,h,w); //pictureBox1在(0,0)到(h,w)范围画点

pictureBox1.Image=MyImage;     //这个图片贴到pictureBox1控件上

2.在窗体上绘制图形

 

System.Drawing.Pen myPen = new System.Drawing.Pen(System.Drawing.Color.Red);//画笔

System.Drawing.SolidBrush myBrush = new System.Drawing.SolidBrush(System.Drawing.Color.Red);//画刷

System.Drawing.Graphics formGraphics = this.CreateGraphics();

formGraphics.FillEllipse(myBrush, new Rectangle(0,0,100,200));//画实心椭圆

formGraphics.DrawEllipse(myPen, new Rectangle(0,0,100,200));//空心圆

formGraphics.FillRectangle(myBrush, new Rectangle(0,0,100,200));//画实心方

formGraphics.DrawRectangle(myPen, new Rectangle(0,0,100,200));//空心矩形

formGraphics.DrawLine(myPen, 0, 0, 200, 200);//画线

formGraphics.DrawPie(myPen,90,80,140,40,120,100); //画馅饼图形

//画多边形

formGraphics.DrawPolygon(myPen,new Point[]{ new Point(30,140), new Point(270,250), new Point(110,240), new Point

(200,170), new Point(70,350), new Point(50,200)});   

//清理使用的资源

myPen.Dispose();

myBrush.Dispose();

formGraphics.Dispose();

3.在窗体上绘制文本

 

//在窗体上绘制竖向文本

System.Drawing.Graphics formGraphics = this.CreateGraphics();

string drawString = "Text";

System.Drawing.Font drawFont = new System.Drawing.Font("Arial", 16);

System.Drawing.SolidBrush drawBrush = new System.Drawing.SolidBrush(System.Drawing.Color.Black);

float x = 150.0f;

float y = 50.0f;

System.Drawing.StringFormat drawFormat = new System.Drawing.StringFormat(StringFormatFlags.DirectionVertical);//文本

//垂直

formGraphics.DrawString(drawString, drawFont, drawBrush, x, y);//绘制文本

formGraphics.DrawString(drawString, drawFont, drawBrush, x, y, drawFormat);//绘制垂直文本

//清理使用的资源

drawFont.Dispose();

drawBrush.Dispose();

formGraphics.Dispose();

4.其他画笔

 

//该画刷的HatchStyle有DiagonalCross、 ForwardDiagonal、Horizontal、 Vertical、 Solid等不同风格

HatchStyle hs = HatchStyle.Cross; //十字

HatchBrush sb = new HatchBrush(hs,Color.Blue,Color.Red);

g.FillRectangle(sb,50,50,150,150);

Rectangle r = new Rectangle(500, 300, 100, 100);

LinearGradientBrush lb = new LinearGradientBrush(r, Color.Red, Color.Yellow, LinearGradientMode.BackwardDiagonal);

g.FillRectangle(lb, r);

//PathGradientBrush路径渐变，LinearGradientBrush线性渐变

Image bgimage = new Bitmap("E:2065215396.jpg");

brush = new TextureBrush(bgimage); //易一幅图作椭圆的背景

g.FillEllipse(brush,50,50,500,300);

5.其他技巧

 

复制代码代码示例:

//申请画图区域

System.Drawing.Rectangle rectangle = new System.Drawing.Rectangle(100, 100, 200, 200);

//创建笔

System.Drawing.Pen myPen = new System.Drawing.Pen(System.Drawing.Color.Black);

myPen.DashStyle=DashStyle.Dash //DashStyle有Dash、DashDot、DashDotDot、Dot、Solid等风格

//创建单色画刷

System.Drawing.SolidBrush myBrush = new System.Drawing.SolidBrush(System.Drawing.Color.Black);

//画图函数

protected override void OnPaint ( System.Windows.Forms.PaintEventArgs e )   

{

}

//颜色对话框

ColorDialog c = new ColorDialog();

c.ShowDialog();

textBox1.BackColor = c.Color;

//字体对话框

FontDialog f = new FontDialog();

f.ShowDialog();

textBox1.Font   = flg.Font;

//RGB的使用

int Red=(int)SelfPlaceKey.GetValue("Red");

int Green=(int)SelfPlaceKey.GetValue("Green");

int Blue=(int)SelfPlaceKey.GetValue("Blue");

BackColor=Color.FromArgb(Red,Green,Blue);

//字体

Font aFont=new Font("Arial",16,FontStyle.Bold|FontStyle.Italic);

rect=new Rectangle(0,y,400,aFont.Height);

g.DrawRectangle(Pens.Blue,rect);

StringFormat sf=new StringFormat();

sf.Alignment=StringAlignment.Far;

g.DrawString("This text is right justified.",aFont,Brushes.Blue,rect,sf);

y+=aFont.Height+20;

aFont.Dispose();