Unity component to read uDesktopDuplication (or other) texture as single colour

DesktopCapture.cs

using UnityEngine;
using System;

public class DesktopCapture : MonoBehaviour
{
    [SerializeField]
    uDesktopDuplication.Texture uddTexture;
    public Light spotLight; 

    [Tooltip("Power of 2 to use for the texture size")]
    [Range(1, 11)]
    public int size = 5;

    RenderTexture[] rtArr;
    Texture2D pxTex;
    public void InitRT(int rtCount) {
        rtArr = new RenderTexture[rtCount];
        for (int i = 0; i < rtArr.Length; i++) {
            rtArr[i] = new RenderTexture((int)Math.Pow(2, i), (int)Math.Pow(2, i), 0);
            rtArr[i].Create();
        }
        pxTex = new Texture2D(1, 1, TextureFormat.ARGB32, false);
    }
    public Color CalculateColor(Texture2D tex) {
        Graphics.Blit(tex, rtArr[size - 1]);
        for (int i = size - 1; i > 0; i-- ) {
            Graphics.Blit(rtArr[i], rtArr[i - 1]);
        }
        RenderTexture.active = rtArr[0];
        pxTex.ReadPixels(new Rect(0, 0, 1, 1), 0, 0);
        pxTex.Apply();
        return pxTex.GetPixel(0, 0);
    }
    private void Start() {
        InitRT(size);
    }
    private void Update() {
        if (uddTexture.monitor != null && uddTexture.monitor.texture != null) {
            spotLight.color = CalculateColor(uddTexture.monitor.texture);
        }
        else {
            Debug.Log("uDD monitor or texture not set");
        }
    }
}