Fade Out Background Based On Movement or Lack Thereof (Webcam Texture)

Hi Unity!

So I've been tasked with creating a system that fades out the background of a webcam texture based on movement, or lack thereof. The user will be holding a cellphone and using the camera facing them, whilst spinning around slowly. This means that while their background will change, their position in the image will not.

So here is my code, which fails to do much of anything. I'm new to Get/SetPixels though - so go easy on me. Any thoughts? I would obviously need to include a lot more refinement, but I thought this would at least give me the basic effect.

     public RawImage webTexImage, mask; //The webTexImage is the image we will project our webcamtexture onto. The mask is the texture that will be infront of it to mask it.
     public float threshold; //The threshold of color variation
 
     void Start()
     {
         WebCamTexture webTex = new WebCamTexture(Screen.width, Screen.height); //Initialize our webcam texture
         webTexImage.texture = webTex; //Set our webcamtexture to the proper component's texture
         webTex.Play(); //play our webcam texture
         StartCoroutine(GetMask()); //Start getting the mask to mask our webcam texture
     }
 
     IEnumerator GetMask()
     {
         //Create a new texture for us to assign to our mask later
         Texture2D texture = new Texture2D(webTexImage.mainTexture.width / 100, webTexImage.mainTexture.height / 100, TextureFormat.ARGB32, false);
         //Define the "old" web texture 
         Texture2D oldWebTex = new Texture2D(webTexImage.mainTexture.width, webTexImage.mainTexture.height, TextureFormat.ARGB32, false) as Texture2D;
         //Wait a frame so that we can get a more recent view of our web texture
         yield return new WaitForEndOfFrame();
         //Define the "new" web texture
         Texture2D newWebTex = new Texture2D(webTexImage.mainTexture.width, webTexImage.mainTexture.height, TextureFormat.ARGB32, false) as Texture2D;
         //Iterate through the entire mask texture and compare each "new" pixel to it's respective "old" pixel
         //If the new pixel's color is close enough to it's respective old pixel, set the mask to black (in mask terms, this means show the pixel).
         //If the new pixel's color is not close enough to it's repective old pixel, set the mask pixel to clear (in mask terms, this means do not show the pixel).
         for (int x = 0; x < texture.width; x++)
         {
             for (int y = 0; y < texture.height; y++)
             {
                 Texture2D o_tex = oldWebTex, n_tex = newWebTex;
                 float old_r = o_tex.GetPixel(x, y).r, old_g = o_tex.GetPixel(x, y).g, old_b = o_tex.GetPixel(x, y).b;
                 float new_r = n_tex.GetPixel(x, y).r, new_g = n_tex.GetPixel(x, y).g, new_b = n_tex.GetPixel(x, y).b;
 
                 if (old_r > (new_r - threshold) && old_r < (new_r + threshold) &&
                     old_g > (new_g - threshold) && old_g < (old_g + threshold) &&
                     old_b > (new_b - threshold) && old_b < (old_b + threshold))
                 {
                     texture.SetPixel(x, y, Color.black);
                 }
                 else
                 {
                     texture.SetPixel(x, y, Color.clear);
                 }
             }
         }
 
         // Apply all SetPixel calls
         texture.Apply();
 
         //Set the texture to the mask
         mask.texture = texture;
         //Repeat the process for the next frame
         StartCoroutine(GetMask());
     }