using System;
using System.Windows.Forms;
using System.Drawing;//绘图要用
using System.Threading;//延时函数要用

namespace 截屏
{
  public partial class Form1 : Form
  {
    bool mouseDown = false, havePainted = false;
    Point start, end;
    Point start1, end1;
    Size size = new Size(0, 0);
    bool saveFile = true;
    public Form1()
    {
      InitializeComponent();
    }

    private void button1_Click(object sender, EventArgs e)
    {
      ReadyToCaptrue();
      saveFile = true;
    }

    private void Form1_MouseDown(object sender, MouseEventArgs e)
    {
      start = e.Location;
      mouseDown = true;
    }

    private void Form1_MouseUp(object sender, MouseEventArgs e)
    {
      if (size.Width != 0 && size.Height != 0)
      {
        ControlPaint.DrawReversibleFrame(new Rectangle(start1, size), Color.Transparent, FrameStyle.Dashed);
        havePainted = false;
      }
      end = e.Location;
      if (start.X > end.X)
      {
        int temp = end.X;
        end.X = start.X;
        start.X = temp;
      }

      if (start.Y > end.Y)
      {
        int temp = end.Y;
        end.Y = start.Y;
        start.Y = temp;
      }
      this.Opacity = 0.0;
      Thread.Sleep(200);
      if (end.X - start.X > 0 && end.Y - start.Y > 0)
      {
        Bitmap bit = new Bitmap(end.X - start.X, end.Y - start.Y);
        Graphics g = Graphics.FromImage(bit);
        g.CopyFromScreen(start, new Point(0, 0), bit.Size);
        if (saveFile)
        {
          SaveFileDialog saveFileDialog = new SaveFileDialog();
          saveFileDialog.Filter = "png|*.png|bmp|*.bmp|jpg|*.jpg|gif|*.gif";
          if (saveFileDialog.ShowDialog() != DialogResult.Cancel)
          {
            bit.Save(saveFileDialog.FileName);
          }
        }
        else
        {
          Clipboard.SetImage(bit);
        }
        g.Dispose();
      }
      this.WindowState = FormWindowState.Normal;
      this.FormBorderStyle = FormBorderStyle.FixedSingle;
      panel1.Visible = true;
      this.Opacity = 1;
      mouseDown = false;
    }

    private void Form1_MouseMove(object sender, MouseEventArgs e)
    {
      if (mouseDown)
      {
        if (size.Width != 0 && size.Height != 0 && havePainted)
        {
          ControlPaint.DrawReversibleFrame(new Rectangle(start1, size), Color.Transparent, FrameStyle.Dashed);
        }
        end1 = e.Location;
        size.Width = Math.Abs(end1.X - start.X);
        size.Height = Math.Abs(end1.Y - start.Y);
        start1.X = (start.X > end1.X) ? end1.X : start.X;
        start1.Y = (start.Y > end1.Y) ? end1.Y : start.Y;

        if (size.Width != 0 && size.Height != 0)
        {
          ControlPaint.DrawReversibleFrame(new Rectangle(start1, size), Color.Transparent, FrameStyle.Dashed);
          havePainted = true;
        }
      }
    }

    private void button2_Click(object sender, EventArgs e)
    {
      ReadyToCaptrue();
      saveFile = false;
    }

    private void Form1_Load(object sender, EventArgs e)
    {

    }

    private void ReadyToCaptrue()
    {
      this.Opacity = 0.1;
      panel1.Visible = false;
      this.FormBorderStyle = FormBorderStyle.None;
      this.WindowState = FormWindowState.Maximized;
    }
  }
}