{
        Rectangle bounds = new Rectangle(this.Location, this.Size);
        Bitmap bitmap = new Bitmap(bounds.Width, bounds.Height);
        Graphics g = Graphics.FromImage(bitmap);
        g.CopyFromScreen(this.Location, Point.Empty, bounds.Size);
        Bitmap bp2 = new Bitmap(bitmap); //  local copy of image...
        pictureBox1.Image = bp2;
    }

{
        this.StartPosition = FormStartPosition.Manual;  // get current window location
        Point cur = this.Location;
        this.Location = new Point(-500, -500);  //  hide the active app off screen.

        Rectangle bounds = new Rectangle(cur, this.Size);
        Bitmap bitmap = new Bitmap(bounds.Width, bounds.Height);
        Graphics g = Graphics.FromImage(bitmap);
        g.CopyFromScreen(cur, Point.Empty, bounds.Size);
        Bitmap bp2 = new Bitmap(bitmap); //  local copy of image...
        pictureBox1.Image = bp2;

        this.Location = cur;  // restore application location
    }

using System;
using System.ComponentModel;
using System.Drawing;
using System.Windows.Forms;
using System.Runtime.InteropServices;

class Magnifier : Control {
    public Magnifier() {
        if (!MagInitialize()) throw new NotSupportedException();
        timer = new Timer { Interval = 45 };
        timer.Tick += (o, ea) => { if (trackMouse) setSource(false); else Invalidate(); };
    }
    [DefaultValue(false)]
    public bool TrackMouse {
        get { return trackMouse; }
        set { trackMouse = value; setSource(false); }
    }
    [DefaultValue(2.0f)]
    public float Magnification {
        get { return magnification; }
        set { magnification = Math.Max(1, value); setSource(true); }
    }

    protected override CreateParams CreateParams {
        get {
            var cp = base.CreateParams;
            if (!this.DesignMode) {
                cp.ClassName = "Magnifier";
                //cp.Style |= MS_SHOWMAGNIFIEDCURSOR;
                this.SetStyle(ControlStyles.UserPaint, true);
            }
            return cp;
        }
    }

    protected override void OnHandleCreated(EventArgs e) {
        base.OnHandleCreated(e);
        if (!this.DesignMode) {
            setSource(true);
            this.FindForm().LocationChanged += ParentLocationChanged;
            timer.Start();
        }
    }
    protected override void Dispose(bool disposing) {
        if (disposing) {
            var frm = this.FindForm();
            if (frm != null) frm.LocationChanged -= ParentLocationChanged;
            timer.Dispose();
            MagUninitialize();
        }
        base.Dispose(disposing);
    }

    private void ParentLocationChanged(object sender, EventArgs e) {
        if (!trackMouse) setSource(false);
    }
    protected override void OnSizeChanged(EventArgs e) {
        setSource(false);
        base.OnSizeChanged(e);
    }
    protected override void OnMouseWheel(MouseEventArgs e) {
        this.Magnification += e.Delta / 100f;
        ((HandledMouseEventArgs)e).Handled = true;
    }

    private void setSource(bool newmag) {
        if (!this.IsHandleCreated || this.DesignMode) return;
        if (newmag) {
            var xform = new MAGTRANSFORM();
            xform.v11 = xform.v22 = magnification;
            xform.v33 = 1.0f;
            MagSetWindowTransform(this.Handle, ref xform);
        }
        Point center;
        if (trackMouse) center = Cursor.Position;
        else {
            var rc = this.RectangleToScreen(this.Bounds);
            center = new Point(rc.Left + rc.Width / 2, rc.Top + rc.Height / 2);
        }
        var scr = Screen.FromPoint(center);
        var rect = new RECT();
        rect.left = Math.Max(scr.Bounds.Left, center.X - (int)(this.Width / magnification / 2));
        rect.top = Math.Max(scr.Bounds.Top, center.Y - (int)(this.Height / magnification / 2));
        rect.right = rect.left + (int)(this.Width / magnification);
        if (rect.right > scr.Bounds.Right) {
            rect.right = scr.Bounds.Right;
            rect.left = rect.right - (int)(this.Width / magnification);
        }
        rect.bottom = center.Y + (int)(this.Height / magnification);
        if (rect.bottom > scr.Bounds.Bottom) {
            rect.bottom = scr.Bounds.Bottom;
            rect.top = rect.bottom - (int)(this.Height / magnification);
        }
        MagSetWindowSource(this.Handle, ref rect);
        this.Invalidate();
    }

    private Timer timer;
    private bool trackMouse;
    private float magnification = 2.0f;

    private struct RECT {
        public int left, top, right, bottom;
    }
    private struct MAGTRANSFORM {
        public float v11, v12, v13;
        public float v21, v22, v23;
        public float v31, v32, v33;
    }
    [DllImport("magnification.dll")]
    private static extern bool MagInitialize();
    [DllImport("magnification.dll")]
    private static extern bool MagUninitialize();
    [DllImport("magnification.dll")]
    private static extern bool MagSetWindowSource(IntPtr hWnd, ref RECT rc);
    [DllImport("magnification.dll")]
    private static extern bool MagSetWindowTransform(IntPtr hWnd, ref MAGTRANSFORM xform);
    private const int MS_SHOWMAGNIFIEDCURSOR = 1;
    private const int MS_CLIPAROUNDCURSOR = 2;
    private const int MS_INVERTCOLORS = 4;
}