图像混合模式 正片叠底、滤色、叠加

public class OverlayBlendModeTest : MonoBehaviour
{
    // 两张需要混合的图片
    public Texture2D ima1;
    public Texture2D ima2;

    public float Opacity = 0.1f;

    private Texture2D tex;

    void Start()
    {
         tex = new Texture2D(ima1.width, ima1.height, TextureFormat.ARGB32, false);
    }

    void Update()

    {   //设置混合度  逐像素读取混合
        Texture2dHandle.SetOpacity = Opacity;
        for (int y = 0; y < ima1.height; y++)
        {
            for (int x = 0; x < ima1.width; x++)
            {

                var dC = ima1.GetPixel(x, y);
                var uC = ima2.GetPixel(x, y);
                var oC = Texture2dHandle.OverlayBlendMode(uC, dC);
                tex.SetPixel(x, y, oC);

            }
        }

        tex.Apply();
        gameObject.GetComponent<Renderer>().material.mainTexture = tex;
    }
}

public class Texture2dHandle
{

 /// <summary>
    /// 混合度
    /// </summary>
    private static float Opacity = 0.3f;

    /// <summary>
    /// 设置混合度
    /// </summary>
    public static float SetOpacity
    {
        set
        {
            if (value < 0)
                value = 0;
            else if (value > 1)
                value = 1;

            Opacity = value;
        }
    }

    /// <summary>
    /// 正片叠底
    /// </summary>
    /// <returns></returns>
    public static Color Multiply(Color b, Color t)
    {
        //b.g *= t.g;
        //b.b *= t.b;
        //b.r *= t.r;
        //b.a = 1;     
   
        var c = new Color(b.r * t.r, b.g * t.g, b.b * t.b, 1);
        return Color.Lerp(b, c, Opacity);
    }

    /// <summary>
    /// 滤色
    /// </summary>
    /// <param name="b"></param>
    /// <param name="t"></param>
    /// <returns></returns>
    public static Color Screen(Color b, Color t)
    {
        b = Minus(b);
        t = Minus(t);

        var c = Minus(Multiply(Multiply(b, t), 2.0f));

        return Color.Lerp(b, c, Opacity);
    }

    /// <summary>
    /// 叠加
    /// </summary>
    /// <param name="b"></param>
    /// <param name="t"></param>
    /// <returns></returns>
    public static Color OverlayBlendMode(Color b, Color t)
    {

        Color c = new Color();
        c.r = OverlayBlendMode(b.r, t.r);
        c.g = OverlayBlendMode(b.g, t.g);
        c.b = OverlayBlendMode(b.b, t.b);
        c.a = 1;

        return Color.Lerp(b, c, Opacity);
    }


    private static float OverlayBlendMode(float basePixel, float blendPixel)
    {
        if (basePixel < 0.5)
        {
            return (float)(2.0 * basePixel * blendPixel);
        }


        return (float)(1.0 - 2.0 * (1.0 - basePixel) * (1.0 - blendPixel));
    }

    /// <summary>
    /// 倍数
    /// </summary>
    /// <param name="c"></param>
    /// <param name="index"></param>
    /// <returns></returns>
    private static Color Multiply(Color c, float index = 1)
    {
        c.r *= index;
        c.g *= index;
        c.b *= index;
        return c;
    }

    private static Color Minus(Color c, int index = 1)
    {
        c.r = index - c.r;
        c.b = index - c.b;
        c.g = index - c.g;
        return c;
    }
}