这个截图模仿QQ截图，左键单击开始截图，鼠标移动出现方框确定截图尺寸，放开时为最终尺寸，双击鼠标弹出保存对话框进行保存。

还有一点就是，如果截图尺寸方框已经确定，移动鼠标到所选区域内时，鼠标会变手型，可以拖动该方框到任意地方进行截图。

建立ScreenCutter解决方案，在其下建立两个windows窗体，一个为MainForm，一个为ScreenBody。

在MainForm中放一个按钮，点击按钮时，获取整个桌面为背景图片，调用ScreenBody。

MainForm的代码为：

using System.Data;using System.Drawing;using System.Linq;using System.Text;using System.Windows.Forms;namespace MainForm{    public partial class MainForm : Form    {        public MainForm()        {            InitializeComponent();        }        private void button1_Click(object sender, EventArgs e)        {            Image img = new Bitmap(Screen.AllScreens[0].Bounds.Width, Screen.AllScreens[0].Bounds.Height);            Graphics g = Graphics.FromImage(img);            g.CopyFromScreen(new Point(0, 0), new Point(0, 0), Screen.AllScreens[0].Bounds.Size);            ScreenBody body = new ScreenBody();            body.BackgroundImage = img;            body.Show();         }    }}

然后设计ScreenBody，设置FormBorderStyle属性为None，再调用load、mousedoubleclick、mousedown、mousemove和mouseup事件即可。

代码如下：

using System;using System.Data;using System.Drawing;using System.Drawing.Imaging;using System.Text;using System.Windows.Forms;namespace MainForm{    public partial class ScreenBody : Form    {        public ScreenBody()        {            InitializeComponent();        }        private Graphics MainPainter;   //主画面        private Pen pen;                //画笔        private bool isDowned;          //判断鼠标是否按下         private bool RectReady;         //矩形是否绘制完成         private Image baseImage;        //基本图形(原来的画面)         private Rectangle Rect;         //就是要保存的矩形         private Point downPoint;        //鼠标按下的点         int tmpx;        int tmpy;        //加载初始化        private void ScreenBody_Load(object sender, EventArgs e)        {            this.WindowState = FormWindowState.Maximized;            MainPainter = this.CreateGraphics();            pen = new Pen(Brushes.Blue);            isDowned = false;            baseImage = this.BackgroundImage;            Rect = new Rectangle();            RectReady = false;        }        //双击保存        private void ScreenBody_MouseDoubleClick(object sender, MouseEventArgs e)        {            if (e.Button == MouseButtons.Left && Rect.Contains(e.X, e.Y))            {                Image memory = new Bitmap(Rect.Width, Rect.Height);                Graphics g = Graphics.FromImage(memory);                g.CopyFromScreen(Rect.X + 1, Rect.Y + 1, 0, 0, Rect.Size);                //Clipboard.SetImage(memory);                string filePath = null;                SaveFileDialog saveFileDialog1 = new SaveFileDialog();                saveFileDialog1.RestoreDirectory = true;                saveFileDialog1.Filter = "Image files (JPeg, Gif, Bmp, etc.)|*.jpg;*.jpeg;*.gif;*.bmp;*.tif; *.tiff; *.png|" +                "JPeg files (*.jpg;*.jpeg)|*.jpg;*.jpeg |GIF files (*.gif)|*.gif |BMP files (*.b" +                "mp)|*.bmp|Tiff files (*.tif;*.tiff)|*.tif;*.tiff|Png files (*.png)| *.png |All f" +                "iles (*.*)|*.*";                if (saveFileDialog1.ShowDialog() == DialogResult.OK)                {                    filePath = saveFileDialog1.FileName.ToString();                    memory.Save(filePath, ImageFormat.Jpeg);                }                      this.Close();            }        }        //左击开始截图或移动，右击撤销        private void ScreenBody_MouseDown(object sender, MouseEventArgs e)        {            if (e.Button == MouseButtons.Left)            {                isDowned = true;                if (RectReady == false)                {                    Rect.X = e.X;                    Rect.Y = e.Y;                    downPoint = new Point(e.X, e.Y);                }                if (RectReady == true)                {                    tmpx = e.X;                    tmpy = e.Y;                }            }            if (e.Button == MouseButtons.Right)            {                this.Close();                return;            }        }        //左键放开，截图方框完成        private void ScreenBody_MouseUp(object sender, MouseEventArgs e)        {            if (e.Button == MouseButtons.Left)            {                isDowned = false;                RectReady = true;            }        }        //鼠标移动，画框或者拖动        private void ScreenBody_MouseMove(object sender, MouseEventArgs e)        {            if (RectReady == false)            {                if (isDowned == true)                {                    Image New = DrawScreen((Image)baseImage.Clone(), e.X, e.Y);                    MainPainter.DrawImage(New, 0, 0);                    New.Dispose();                }            }            if (RectReady == true)            {                if (Rect.Contains(e.X, e.Y))                {                    this.Cursor = Cursors.Hand;                    if (isDowned == true)                    {                        //和上一次的位置比较获取偏移量                         Rect.X = Rect.X + e.X - tmpx;                        Rect.Y = Rect.Y + e.Y - tmpy;                        //记录现在的位置                         tmpx = e.X;                        tmpy = e.Y;                        MoveRect((Image)baseImage.Clone(), Rect);                    }                }                else                 {                    this.Cursor = Cursors.Arrow;                }            }        }        //画屏幕        private Image DrawScreen(Image back, int Mouse_x, int Mouse_y)        {            Graphics Painter = Graphics.FromImage(back);            DrawRect(Painter, Mouse_x, Mouse_y);            return back;        }        //画矩形        private void DrawRect(Graphics Painter, int Mouse_x, int Mouse_y)        {            int width = 0;            int heigth = 0;            try            {                if (Mouse_y < Rect.Y)                {                    Rect.Y = Mouse_y;                    heigth = downPoint.Y - Mouse_y;                }                else                {                    heigth = Mouse_y - downPoint.Y;                }                if (Mouse_x < Rect.X)                {                    Rect.X = Mouse_x;                    width = downPoint.X - Mouse_x;                }                else                {                    width = Mouse_x - downPoint.X;                }            }            catch (Exception ee)            {                MessageBox.Show("cuo");            }            finally            {                Rect.Size = new Size(width, heigth);                Painter.DrawRectangle(pen, Rect);            }        }        //移动矩形        private void MoveRect(Image image, Rectangle Rect)        {            Graphics Painter = Graphics.FromImage(image);            Painter.DrawRectangle(pen, Rect.X, Rect.Y, Rect.Width, Rect.Height);            MainPainter.DrawImage(image, 0, 0);            image.Dispose();        }    }}

winform实现截图