private void contrastToolStripMenuItem_Click(object sender, EventArgs e)
        {
            try
            {
                Parameter dlg = new Parameter();
                dlg.nValue = 0;

                if (DialogResult.OK == dlg.ShowDialog())
                {
                    Bitmap m_Bitmap = (Bitmap)pic_box.Image;
                    undo_picture = m_Bitmap;
                    Bitmap mm_bit = (Bitmap)m_Bitmap.Clone();
                    if (BitmapFilter.Contrast(mm_bit, (sbyte)dlg.nValue))
                        this.Invalidate();

                    pic_box.Image = (Bitmap)mm_bit;
                    pic_box.Invalidate();
                }
            }
            catch
            {

            }
        }