Merging 2 Textures Into 1

I am trying to merge two textures into one with little sucess. One texture is a border with a UI mask in the middle and the second texture is a picture of the user, taken with the camera of a mobile device. When the user takes the picture it is saved as a photo of him togther with the border. The problem is, I cant really understand who merging 2 textures work. I get an image but the colors are blurry. This is the code I am using:

 public class MergeTextures : MonoBehaviour {
     
     public RawImage image;
     public Texture2D tex1;
     public Texture2D tex2;
     
     public void Merge()
     {
         Color[] tex1Pix = tex1.GetPixels();
         Color[] tex2Pix = tex2.GetPixels();
         
         int width = (tex1.width >= tex2.width) ? tex1.width : tex2.width;
         int height = (tex1.height >= tex2.height) ? tex1.height : tex2.height;
         
         Color[] biggerArray = (tex1Pix.Length >= tex2Pix.Length) ? tex1Pix : tex2Pix;
         Color[] smallerArray = (biggerArray == tex1Pix) ? tex2Pix : tex1Pix;
                 
         for(int i = 0; i < smallerArray.Length; i++)
             biggerArray[i] += smallerArray[i];
         
         Texture2D photo = new Texture2D(width, height);
         photo.SetPixels(biggerArray);
         photo.Apply();
         
         image.texture = photo;
         image.SetNativeSize();
     }
 }

I will appreciate any help!