Code int width = Screen.PrimaryScreen.Bounds.Width; int height = Screen.PrimaryScreen.Bounds.Height; Bitmap bmp = new Bitmap(width, height); using (Graphics g = Graphics.FromImage(bmp)) {     g.CopyFromScreen(0, 0, 0, 0, new Size(width, height)); }

Code public partial class FullScreenForm : Form {     private Rectangle rectSelected = Rectangle.Empty;     private bool isClipping = false;     private Bitmap screen;     private Bitmap coverLayer = null;     private Color coverColor;     private Brush rectBrush = null;     private Bitmap resultBmp = null;     public FullScreenForm(Bitmap screen) {         InitializeComponent();         int width = Screen.PrimaryScreen.Bounds.Width;         int height = Screen.PrimaryScreen.Bounds.Height;         coverLayer = new Bitmap(width, height);         coverColor = Color.FromArgb(50, 200, 0, 0);         rectBrush = new SolidBrush(coverColor);         using (Graphics g = Graphics.FromImage(coverLayer)) {             g.Clear(coverColor);         }         this.Bounds = new Rectangle(0, 0, width, height);         this.screen = screen;         this.DoubleBuffered = true;     }     protected override void OnMouseDown(MouseEventArgs e) {         if (e.Button == MouseButtons.Left) {             isClipping = true;             rectSelected.Location = e.Location;         }         else if (e.Button == MouseButtons.Right) {             this.DialogResult = DialogResult.OK;         }     }     protected override void OnMouseMove(MouseEventArgs e) {         if (e.Button == MouseButtons.Left && isClipping) {             rectSelected.Width = e.X - rectSelected.X;             rectSelected.Height = e.Y - rectSelected.Y;             this.Invalidate();         }     }     protected override void OnMouseUp(MouseEventArgs e) {         if (e.Button == MouseButtons.Left && isClipping) {             rectSelected.Width = e.X - rectSelected.X;             rectSelected.Height = e.Y - rectSelected.Y;             this.Invalidate();             resultBmp = new Bitmap(rectSelected.Width, rectSelected.Height);             using (Graphics g = Graphics.FromImage(resultBmp)) {                 g.DrawImage(screen,new Rectangle(0, 0, rectSelected.Width, rectSelected.Height), rectSelected, GraphicsUnit.Pixel);             }             this.DialogResult = DialogResult.OK;         }     }     protected override void OnPaint(PaintEventArgs e) {         Graphics g = e.Graphics;         g.DrawImage(screen, 0, 0);         g.DrawImage(coverLayer, 0, 0);         PaintRectangle();     }     protected override void OnPaintBackground(PaintEventArgs e) {     }     protected override void OnKeyDown(KeyEventArgs e) {         if (e.KeyCode == Keys.Escape) {             this.DialogResult = DialogResult.Cancel;         }     }     private void PaintRectangle() {         using (Graphics g = Graphics.FromImage(coverLayer)) {             g.Clear(coverColor);             GraphicsPath path = new GraphicsPath();             path.AddRectangle(this.Bounds);             path.AddRectangle(rectSelected);             g.FillPath(rectBrush, path);             g.DrawRectangle(Pens.Blue, rectSelected);         }     }     public Bitmap ResultBitmap {         get { return resultBmp; }     } }