private Bitmap ReadRGBA(string filename)
        {
            if (string.IsNullOrEmpty(filename))
                throw new ArgumentException(filename);
            Bitmap source = new Bitmap(filename);
            Bitmap result = new Bitmap(source.Width,source.Height,PixelFormat.Format24bppRgb);
            for (int i = 0; i < source.Width; i++)
            {
                for (int j = 0; j < source.Height; j++)
                {
                    var color = source.GetPixel(i, j);
                    result.SetPixel(i,j,Color.FromArgb(color.A,color.B,color.G,color.R));
                }
            }
            return result;
        }