Unity Grayscale Setup

Grayscale.cs

using UnityEngine;

[RequireComponent (typeof (SpriteRenderer))]
public class Grayscale : MonoBehaviour
{
    void Start ( )
    {
        SpriteRenderer renderer = GetComponent<SpriteRenderer> ( );
        Sprite sprite = renderer.sprite;
        Texture2D srcTexture = sprite.texture;

        int width = srcTexture.width;
        int height = srcTexture.height;
        Color[ ] srcPixels = srcTexture.GetPixels (0, 0, width, height);
        int len = srcPixels.Length;

        Texture2D trgTexture = new Texture2D (width, height);
        Color[ ] trgPixels = new Color[len];
        
        for (int i = 0; i < len; ++i)
        {
            int x = i % width;
            int y = i / width;
            Color srcPixel = srcPixels[i];
            float gray = GrayMethod (srcPixel);
            trgPixels[i] = new Color (
                gray, gray, gray,
                srcPixel.a);
        }

        trgTexture.SetPixels (trgPixels);
        trgTexture.Apply ( );

        renderer.sprite = Sprite.Create (
            trgTexture,
            new Rect (0, 0, width, height),
            new Vector2 (0.5f, 0.5f));
    }
}