private void Genera_Spettro(string filename)
        {

            FileStream inStream = File.OpenRead(filename);
            WaveReader wr = new WaveReader(inStream);
            this.Wave = wr.Data[0];

            if (this.wave == null)
            {
                this.GenerateSampleWave();
            }
            if (this.wave.Length > 0)
            {
               // qui dove carico la bitmap.

                Bitmap bmp = new Bitmap(pictureBox1.Width - 1, pictureBox1.Height - 1);
                Graphics g = Graphics.FromImage(bmp);
                Rectangle bounds = new Rectangle(0, 0, this.Width - 1, this.Height - 1);

                Color frmColor = this.BackColor;
                Brush bckColor;

                alpha = (opacity * 255) / 100;

                if (drag)
                {
                    Color dragBckColor;

                    if (BackColor != Color.Transparent)
                    {
                        int Rb = BackColor.R * alpha / 255 + frmColor.R * (255 - alpha) / 255;
                        int Gb = BackColor.G * alpha / 255 + frmColor.G * (255 - alpha) / 255;
                        int Bb = BackColor.B * alpha / 255 + frmColor.B * (255 - alpha) / 255;
                        dragBckColor = Color.FromArgb(Rb, Gb, Bb);
                    }
                    else dragBckColor = frmColor;

                    alpha = 255;
                    bckColor = new SolidBrush(Color.FromArgb(alpha, dragBckColor));
                }
                else
                {
                    bckColor = new SolidBrush(Color.FromArgb(alpha, this.BackColor));
                }

                Pen pen = new Pen(this.ForeColor);

                if (this.BackColor != Color.Transparent | drag)
                {
                    g.FillRectangle(bckColor, bounds);
                }

                int middle = bounds.Top + (int)Math.Round((double)bounds.Height / 2d);
                double factor = Math.Floor(((double)bounds.Height) / 2d) / ((double)this.wave.Max(i => Math.Abs(i - WaveAverage)));
                double dataPerPixel = ((double)this.wave.Length) / ((double)(bounds.Width + 1));
                int length = (int)Math.Ceiling(dataPerPixel);
                int posA = 0;
                if (length == 1)
                {
                    int yA = middle + (int)Math.Round((double)(this.wave[0] - WaveAverage) * factor);
                    int yB = yA;
                    for (int x = bounds.Left + 1; x <= bounds.Right; x++)
                    {
                        int posB = (int)Math.Floor(((double)(x - bounds.Left)) * dataPerPixel);
                        if (posB > posA)
                        {
                            posA = posB;
                            yB = middle + (int)Math.Round((double)(this.wave[posB] - WaveAverage) * factor);
                        }
                        g.DrawLine(pen, new Point(x - 1, yA), new Point(x, yB));
                        yA = yB;
                    }
                }
                else
                {
                    int yA = middle + (int)Math.Round((double)(this.wave[0] - WaveAverage) * factor);
                    int yB = yA;
                    for (int x = bounds.Left + 1; x <= bounds.Right; x++)
                    {
                        int posB = (int)Math.Floor(((double)(x - bounds.Left)) * dataPerPixel);
                        yB = middle + (int)Math.Round((double)(this.wave[posB] - WaveAverage) * factor);
                        if ((posB - posA) > 1)
                        {
                            Int32[] values = new Int32[posB - posA];
                            Array.Copy(wave, posA + 1, values, 0, posB - posA);
                            int max = (int)Math.Round((double)(values.Max() - WaveAverage) * factor);
                            int min = (int)Math.Round((double)(values.Min() - WaveAverage) * factor);
                            if (max == min)
                                g.DrawLine(pen, new Point(x - 1, yA), new Point(x, middle + max));
                            else
                                g.DrawLine(pen, new Point(x, middle + min), new Point(x, middle + max));
                        }
                        else
                        {
                            g.DrawLine(pen, new Point(x - 1, yA), new Point(x, yB));
                        }
                        posA = posB;
                        yA = yB;
                    }
                }
                pictureBox1.Image = bmp;
                pen.Dispose();
                bckColor.Dispose();
                g.Dispose();
            }
        }