Code:
               
        private void drawText()
        {
            // boja teksta
            myWatermarkColor = Color.Red;

            float fontSize = 10;
            string CurrentFile = "slika.jpg";
            string tekstNaSlici = "ovo je slika!";
            Font f;

            try
            {
                f = new Font(FontFamily.GenericMonospace, fontSize);
            }
            catch (Exception e)
            {
                // obrada greške
            }
            
            myFont = f;

            try
            {
                picContainer.Image = Image.FromFile(CurrentFile);
            }
            catch (Exception gre)
            {
                // opet obrada greške, ako fajl ne postoji i sl.
            }

            int opac = 0;  
            int procenat = 50; // procenat neprovidnosti (opacity) fonta

            opac = (int)((double)((double)procenat / (double)100) * 255); // ovo može verovatno elegantnije da se reši :)

            Graphics g;
            //Učitavanje slike
            try
            {
                g = Graphics.FromImage(picContainer.Image);
            }
            catch // nekad ne uspeva da pročita sliku pa mora da se pristupi sledećem:
            {
                Image slika = picContainer.Image;
                try
                {
                    Bitmap bmp = new Bitmap(slika);
                    Bitmap slika2 = new Bitmap(bmp.Width, bmp.Height, PixelFormat.Format24bppRgb);
                    g = Graphics.FromImage(slika2);
                    g.DrawImage(bmp, 0, 0, slika2.Width, slika2.Height);
                    picContainer.Image = slika2;
                }
                catch 
                {
                    return;
                }

            }

            // ovde podešavaš boju i neprovidnost teksta koji ispisuješ
            Brush myBrush = new SolidBrush(Color.FromArgb(opac, myWatermarkColor));
            SizeF sz = g.MeasureString(tekstNaSlici, myFont);
            if (tesktNaSlici != "")
            {
                int X;
                int Y;
                X = 0;
                Y = 0;
                while ((int)Y <= picContainer.Image.Height)
                {
                    while ((int)X <= picContainer.Image.Width)
                    {
                        //ovde ispisuješ tekst navedenim fontom i "četkicom"
                        g.DrawString(tekstNaSlici, myFont, myBrush, new Point(X, Y));
                        X += (int)sz.Width;
                    }
                    X = 0;
                    Y += (int)sz.Height;
                }
            }
            g.Dispose();
                
        }