public Texture2D CombineTexture(Texture2D background, Texture2D top)

    {

        int width = background.width;

        int height = background.height;

        Texture2D ret = new Texture2D(width, height);

        for(int x = ; x < width; x++)

        {

            for(int y = ; y < height; y++)

            {

                ret.SetPixel(x, y, background.GetPixel(x, y));

            }

        }

        int topWidth = top.width;

        int topHeight = top.height;

        int x_start = width /  - topWidth / ;

        int y_start = height /  - topHeight / ;

        for (int x = x_start; x < topWidth + x_start; x++)

        {

            for (int y = y_start; y < topHeight + y_start; y++)

            {

                Color bgColor = background.GetPixel(x, y);

                Color topColor = top.GetPixel(x - x_start, y - y_start);

                ret.SetPixel(x, y, Color.Lerp(bgColor, topColor, topColor.a/1f));

            }

        }

        ret.Apply();

        return ret;

    }