Save webcam with grayscale filter and alpha blend

PrintManager.cs

using System;
using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using UnityEngine.UI;

namespace Fotoprint
{
    public class PrintManager : MonoBehaviour
    {
        private WebCamTexture webcam;
        [SerializeField]
        private RawImage cameraFrame;
        
        [NonSerialized]
        public bool useFrame = false;
        [NonSerialized]
        public bool grayScale = false;
        public Sprite[] frame;


        //todo: optimize 
        private void Update()
        {
            if(webcam != null && !webcam.isPlaying)
            {
                if (grayScale || useFrame)
                {
                    Texture2D snap = new Texture2D(webcam.width, webcam.height);
                    snap.SetPixels(webcam.GetPixels());
                    snap.Apply();
                    
                    if (grayScale)
                    {
                        snap = ToGrayScale(webcam.GetPixels());
                    }

                    if (useFrame)
                    {
                        foreach (Sprite image in frame)
                        {
                            snap = AlphaBlend(snap, image.texture);    
                        }
                    }
                    cameraFrame.texture = snap;
                }
                else
                {
                    cameraFrame.texture = webcam;
                }
                
            }

        }

        //Prints picture
        public void Print()
        {
            Texture2D snap = new Texture2D(webcam.width, webcam.height);
            snap.SetPixels(webcam.GetPixels());
            snap.Apply();
            if (grayScale)
            {
                snap = ToGrayScale(snap);
            }
            if (useFrame)
            {
                foreach (Sprite image in frame)
                {
                    snap = AlphaBlend(snap, image.texture);    
                }
            }
            
            System.IO.File.WriteAllBytes(Application.persistentDataPath+"/foto.png", snap.EncodeToPNG());

            webcam.Stop();
            webcam = null;
        }
        
        public void OpenCamera()
        {
            if (webcam == null)
            {
                var devices = WebCamTexture.devices;
                for( var i = 0 ; i < devices.Length ; i++ )
                {
                    Debug.Log(devices[i].name);
                }

                webcam = new WebCamTexture(devices[0].name,1280,720);
                cameraFrame.texture = webcam;

            }
            webcam.Play();

        }

        public void PauseCamera()
        {
            webcam.Pause();
        }
        public Texture2D ToGrayScale(Texture2D texture)
        {
            var bottomPixelData = texture.GetPixels();
            int count = bottomPixelData.Length;
            var resultData = new Color[count];
            for(int i = 0; i < count; i++)
            {
                Color bottomPixels = bottomPixelData[i];
                Color temp = new Color(
                    (1f-bottomPixels.r),
                    (1f-bottomPixels.g),
                    (1f-bottomPixels.b),
                    (1f-bottomPixels.a));
                resultData[i] = bottomPixels * temp.grayscale * bottomPixels.linear;
            }
            var res = new Texture2D(texture.width, texture.height);
            res.SetPixels(resultData);
            res.Apply();
            return res;
        }
        
        public Texture2D ToGrayScale(Color[] cArr)
        {
            var bottomPixelData = cArr;
            int count = bottomPixelData.Length;
            var resultData = new Color[count];
            for(int i = 0; i < count; i++)
            {
                Color bottomPixels = bottomPixelData[i];
                Color temp = new Color(
                    (1f-bottomPixels.r),
                    (1f-bottomPixels.g),
                    (1f-bottomPixels.b),
                    (1f-bottomPixels.a));
                resultData[i] = bottomPixels * temp.grayscale * bottomPixels.linear;
            }
            var res = new Texture2D(1280, 720);
            res.SetPixels(resultData);
            res.Apply();
            return res;
        }
        
        public Texture2D AlphaBlend(Texture2D textureBottom, Texture2D textureTop)
        {
            if (textureBottom.width != textureTop.width || textureBottom.height != textureTop.height)
                throw new System.InvalidOperationException("AlphaBlend only works with two equal sized images");
            var bottomPixelData = textureBottom.GetPixels();
            var topPixelData = textureTop.GetPixels();
            int count = bottomPixelData.Length;
            var resultData = new Color[count];
            for(int i = 0; i < count; i++)
            {
                Color bottomPixels = bottomPixelData[i];
                Color topPixels = topPixelData[i];

                float srcF = topPixels.a;
                float destF = 1f - topPixels.a;
                float alpha = srcF + destF * bottomPixels.a;
                Color resultColor = (topPixels * srcF + bottomPixels * bottomPixels.a * destF)/alpha;
                resultColor.a = alpha;
                resultData[i] = resultColor;
            }
            var res = new Texture2D(textureBottom.width, textureBottom.height);
            res.SetPixels(resultData);
            res.Apply();
            return res;
        }
        
        public Texture2D AlphaBlend( Color[] cArr, Texture2D textureTop)
        {
            var bottomPixelData = cArr;
            var topPixelData = textureTop.GetPixels();
            int count = bottomPixelData.Length;
            var resultData = new Color[count];
            for(int i = 0; i < count; i++)
            {
                Color bottomPixels = bottomPixelData[i];
                Color topPixels = topPixelData[i];

                float srcF = topPixels.a;
                float destF = 1f - topPixels.a;
                float alpha = srcF + destF * bottomPixels.a;
                Color resultColor = (topPixels * srcF + bottomPixels * bottomPixels.a * destF)/alpha;
                resultColor.a = alpha;
                resultData[i] = resultColor;
            }
            var res = new Texture2D(textureTop.width, textureTop.height);
            res.SetPixels(resultData);
            res.Apply();
            return res;
        }
        
        //NOT WORKING
        // let posx and posy be the placement position of the foreground image
        // let foreground.sizex and foreground.sizey the size of the foreground image
        // for each row of the background image
        // for each column of the background image
        // // check if the position overlaps the foreground image
        // if column - posx >= 0 and column - posx < foreground.sizex
        // if row - posy >= 0 and row - posy < foreground.sizey
        //     alpha blend the background and the foreground
        // else
        // output background value
        public Texture2D AlphaBlend(Texture2D textureBottom, Texture2D textureTop,int x, int y)
        {
            var bottomPixelData = textureBottom.GetPixels();
            var topPixelData = textureTop.GetPixels();
            int count = bottomPixelData.Length;
            var resultData = new Color[count];

            for (int w = 0; w < textureBottom.width; w++)
            {
                for (int h = 0; h < textureBottom.height; h++)
                {
                    if (w - x >= 0 && w - x < textureBottom.width)
                    {
                        if (h - y >= 0 && h - y < textureBottom.height)
                        {
                            Color bottomPixel = textureBottom.GetPixel(w,h);
                            Color topPixel = textureTop.GetPixel(w-x,h-y);

                            float srcF = topPixel.a;
                            float destF = 1f - topPixel.a;
                            float alpha = srcF + destF * bottomPixel.a;
                            //int grayScale = (int)((oc.R * 0.3) + (oc.G * 0.59) + (oc.B * 0.11));
                            Color resultColor = (topPixel * srcF + bottomPixel * bottomPixel.a * destF)/alpha;
                            resultColor.a = alpha;
                            resultData[(w+1)*(h+1)] = resultColor;
                        }
                        else
                        {
                            Color resultColor = textureBottom.GetPixel(w,h);
                            resultColor.a = 1;
                            resultData[w+h] = resultColor;
                        }
                    }
                    else
                    {
                        Color resultColor = textureBottom.GetPixel(w,h);
                        resultColor.a = 1;
                        resultData[w+h] = resultColor;
                    }
                }
            }

            var res = new Texture2D(textureBottom.width, textureBottom.height);
            res.SetPixels(resultData);
            res.Apply();
            return res;
        }
    }
}