Initialize Canvas

Canvas.cs

void Start() {
    if (Camera.main != null) {
        Camera.main.orthographicSize = ORTHOGRAPHIC_SIZE;
    }

    if (FindObjectOfType<EventSystem>() == null) {
        var eventSystem = new GameObject("EventSystem", typeof(EventSystem));
        eventSystem.AddComponent<StandaloneInputModule>();
    }
    
    this.canvasObject         = new GameObject("CanvasUIRoot");
    GameObject.DontDestroyOnLoad(canvasObject);

    Canvas canvas                   = this.canvasObject.AddComponent<Canvas>();
    canvas.renderMode               = RenderMode.ScreenSpaceCamera;
    canvas.pixelPerfect             = false;
    canvas.worldCamera              = Camera.main;
    canvas.sortingOrder             = 10;
    canvas.targetDisplay            = 0;

    CanvasScaler canvasScaler           = this.canvasObject.AddComponent<CanvasScaler>();
    canvasScaler.uiScaleMode            = CanvasScaler.ScaleMode.ScaleWithScreenSize;
    canvasScaler.referenceResolution    = new Vector2(1024, 768);
    canvasScaler.matchWidthOrHeight     = 1;
    canvasScaler.referencePixelsPerUnit = 100;
    
    this.canvasObject.AddComponent<GraphicRaycaster>();

    Canvas prefab = Resources.Load<Canvas>("Prefabs/CanvasUI");
    Canvas gameObjectCanvasUI = Instantiate(prefab) as Canvas;
    gameObjectCanvasUI.name = "CanvasUI";
    gameObjectCanvasUI.transform.SetParent(this.canvasObject.transform, false);
}