OpenTK draw text in Unicode

using System;
using System.Collections.Generic;
using System.Drawing;
using System.Drawing.Text;
using System.Drawing.Drawing2D;
using System.Drawing.Imaging;
using System.Windows.Forms;
using OpenTK;
using OpenTK.Graphics;
using OpenTK.Graphics.OpenGL;
using System.Runtime.InteropServices;
 
namespace OpenTKBitmapTexture
{
	/// <summary>
	/// Description of MainForm.
	/// </summary>
	public partial class MainForm : Form
	{
 
		Color textColor=Color.Green;
		Color backgroundColor=Color.White;
		Font font;
              Bitmap bmp;
        bool loadGL = false;
 
		public MainForm()
		{
			//
			// The InitializeComponent() call is required for Windows Forms designer support.
			//
			InitializeComponent();
			font=new Font(new FontFamily("Times New Roman"),14,FontStyle.Regular);
			//Support Unicode
 
			pictureChooseTextColor.BackColor=textColor;
			pictureChooseColorBackground.BackColor=backgroundColor;
            pictureGDI.BackColor = backgroundColor;
			lblFont.Text=FontString(font);
 
 
            pictureGL.Load += new EventHandler(pictureGL_Load);
            pictureGL.Paint += new PaintEventHandler(pictureGL_Paint);
            pictureGL.Resize += new EventHandler(pictureGL_Resize);
 
			//
			// TODO: Add constructor code after the InitializeComponent() call.
			//
		}
 
		#region Commands
		//Run Project		
		void BtnRunClick(object sender, EventArgs e)
		{
			//MessageBox.Show("Run project",this.Text);
            //loadGL = false;
            DrawGDI();
            DrawGL();
 
		}
 
		//Font Text
		void BtnFontClick(object sender, EventArgs e)
		{
			if(fontDialog.ShowDialog()==DialogResult.OK)
			{
				font=fontDialog.Font;
				lblFont.Text=FontString(font);
                BtnRunClick(sender, e);
			}
		}
 
 
		void PictureChooseTextColorClick(object sender, EventArgs e)
		{
            if (colorTextColorDialog.ShowDialog() == DialogResult.OK)
            {
                textColor = colorTextColorDialog.Color;
                pictureChooseTextColor.BackColor = textColor;
                BtnRunClick(sender, e); 
            } 
 
        }
 
		void PictureChooseColorBackgroundClick(object sender, EventArgs e)
        {
            if (colorBackgroundColorDialog.ShowDialog() == DialogResult.OK)
            {
                backgroundColor = colorBackgroundColorDialog.Color;
                pictureChooseColorBackground.BackColor = backgroundColor;
                BtnRunClick(sender, e); 
            }
 
		}
		#endregion
 
		#region Methods
		String FontString(Font fonts)
		{
			return String.Format("Font: {0}, {1}, {2}.",
			                     fonts.FontFamily.Name,fonts.Size,
			                     fonts.Style.ToString());
		}
 
        void DrawGDI()
        {
            Bitmap tmpFont = new Bitmap(1, 1, System.Drawing.Imaging.PixelFormat.Format32bppArgb);
            SizeF size=Graphics.FromImage(tmpFont).MeasureString(txtBox.Text, font);
            textureHeight = (int)size.Height; textureWidth = (int)size.Width;
 
            if (textureWidth == 0) { textureHeight = 1; textureWidth = 1; }
            bmp = new Bitmap(textureWidth, textureHeight, System.Drawing.Imaging.PixelFormat.Format32bppArgb);       
            Graphics e = Graphics.FromImage(bmp);
            e.Clear(backgroundColor);
            SolidBrush brush=new SolidBrush(textColor);
            e.SmoothingMode = SmoothingMode.HighSpeed;
            e.DrawString(txtBox.Text, font, brush, new PointF(0,0));
 
            pictureGDI.Image = bmp;
            pictureGDI.BackColor = backgroundColor;            
            pictureGDI.Invalidate();
            tmpFont.Dispose();
            e.Dispose();
 
 
        }
 
 
        #region GL Graphics
        int textureWidth = 100, textureHeight = 100;
        void DrawGL()
        {
            loadGL = false;
            pictureGL_Load(new object(), new EventArgs());
            pictureGL.Invalidate();
        }
        void pictureGL_Resize(object sender, EventArgs e)
        {
            SetupViewPort();
            pictureGL.Invalidate();
        }
 
        void pictureGL_Paint(object sender, PaintEventArgs e)
        {
            if (!loadGL) return;
            GL.ClearColor(backgroundColor);
            GL.Clear(ClearBufferMask.ColorBufferBit);
            DrawString();
            pictureGL.SwapBuffers();
        }
 
        int res;
        void pictureGL_Load(object sender, EventArgs e)
        {
            loadGL = true;
            res = loadBitmap(bmp);
            SetupViewPort();
        }
 
        int w, h;
        void SetupViewPort()
        {
            w = pictureGL.Width;
            h = pictureGL.Height;
            if (h == 0) h = 1;
            GL.MatrixMode(MatrixMode.Projection);
            GL.LoadIdentity();
            GL.Viewport(0, 0, w, h);
            GL.Ortho(0f, w, h, 0f, 0f, 1f);
 
 
        }
 
        void DrawString()
        {
            GL.Enable(EnableCap.Texture2D);
            GL.BindTexture(TextureTarget.Texture2D, loadBitmap(bmp));
                 DrawQuad();
            GL.Disable(EnableCap.Texture2D);
        }
 
        void DrawQuad()
        {
            GL.Begin(BeginMode.Quads);
                GL.TexCoord2(0f, 0f); GL.Vertex2(0, 0);
                GL.TexCoord2(0f, 1f); GL.Vertex2(0,(float)textureHeight);
                GL.TexCoord2(1f, 1f); GL.Vertex2((float)textureWidth,(float)textureHeight);
                GL.TexCoord2(1f, 0f); GL.Vertex2((float)textureWidth,0);                
            GL.End();
        }
 
        int loadBitmap(Bitmap image)
        {
            try
            {
                short width = (short)(image.Width);
                short height = (short)(image.Height);
 
                 int bpp = image.PixelFormat == System.Drawing.Imaging.PixelFormat.Format32bppArgb ? 32 : 24;
 
                BitmapData bData = image.LockBits(new Rectangle(new Point(), image.Size),
                ImageLockMode.ReadOnly,
                System.Drawing.Imaging.PixelFormat.Format32bppArgb);
                image.UnlockBits(bData);
 
                int result = GL.GenTexture();
                GL.BindTexture(TextureTarget.Texture2D, result);
 
                GL.TexParameter(TextureTarget.Texture2D, TextureParameterName.TextureWrapS,
                    (int)TextureWrapMode.ClampToEdge);
                GL.TexParameter(TextureTarget.Texture2D, TextureParameterName.TextureWrapT,
                    (int)TextureWrapMode.ClampToEdge);
 
                GL.TexParameter(TextureTarget.Texture2D, TextureParameterName.TextureMagFilter,
                    (int)TextureMagFilter.Linear);
                GL.TexParameter(TextureTarget.Texture2D, TextureParameterName.TextureMinFilter, 
                    (int)TextureMinFilter.Linear);
 
                GL.TexEnv(TextureEnvTarget.TextureEnv, TextureEnvParameter.TextureEnvMode, 
                    (int)TextureEnvMode.Modulate);
 
                GL.TexImage2D(TextureTarget.Texture2D, 0, PixelInternalFormat.Rgba, width, height, 0,
                    OpenTK.Graphics.OpenGL.PixelFormat.Bgra, PixelType.UnsignedByte, bData.Scan0);
 
                return result;
            }
            catch { return -1;  }
        }
		#endregion
 
 
        #endregion
 
 
    }
}