private void ImageShow_Load(object sender, EventArgs e){pictureBox1.Load(@"E:\SQ1.jpg");pictureBox1.SizeMode = PictureBoxSizeMode.Zoom;pictureBox1.Dock = DockStyle.None;}private void pictureBox1_MouseEnter(object sender, EventArgs e){pictureBox1.Focus();pictureBox1.Cursor = Cursors.SizeAll;}/// <summary>/// 放大，缩小图片/// </summary>/// <param name="sender"></param>/// <param name="e"></param>void pictureBox1_MouseWheel(object sender, MouseEventArgs e){int i = e.Delta * SystemInformation.MouseWheelScrollLines / 5;pictureBox1.Width = pictureBox1.Width + i;//增加picturebox的宽度pictureBox1.Height = pictureBox1.Height + i;pictureBox1.Left = pictureBox1.Left - i / 2;//使picturebox的中心位于窗体的中心pictureBox1.Top = pictureBox1.Top - i / 2;//进而缩放时图片也位于窗体的中心}      

private void pictureBox1_MouseDown(object sender, MouseEventArgs e){if (e.Button == MouseButtons.Left){mouseDownPoint.X = Cursor.Position.X;  //注：全局变量mouseDownPoint前面已定义为Point类型  mouseDownPoint.Y = Cursor.Position.Y;isSelected = true;}  }private void pictureBox1_MouseMove(object sender, MouseEventArgs e){if (isSelected && IsMouseInPanel())//确定已经激发MouseDown事件，和鼠标在picturebox的范围内
            {this.pictureBox1.Left = this.pictureBox1.Left + (Cursor.Position.X - mouseDownPoint.X);this.pictureBox1.Top = this.pictureBox1.Top + (Cursor.Position.Y - mouseDownPoint.Y);mouseDownPoint.X = Cursor.Position.X;mouseDownPoint.Y = Cursor.Position.Y;}  }private bool IsMouseInPanel(){if (this.pan_picture.Left < PointToClient(Cursor.Position).X && PointToClient(Cursor.Position).X < this.pan_picture.Left + this.pan_picture.Width && this.pan_picture.Top < PointToClient(Cursor.Position).Y && PointToClient(Cursor.Position).Y < this.pan_picture.Top + this.pan_picture.Height){return true;}else{return false;}}private void pictureBox1_MouseUp(object sender, MouseEventArgs e){isSelected = false;}