a.cs

public GameObject makeCanvas() {
	GameObject canvasObject= new GameObject("Canvas");

	Canvas canvas = canvasObject.AddComponent<Canvas>();
	canvas.renderMode = RenderMode.WorldSpace;

	CanvasScaler scaler = canvasObject.AddComponent<CanvasScaler>();
	scaler.scaleFactor = 10.0f;
	scaler.dynamicPixelsPerUnit = 10.0f;

	GraphicRaycaster graphic = canvasObject.AddComponent<GraphicRaycaster>();

	canvasObject.GetComponent<RectTransform>().SetSizeWithCurrentAnchors(RectTransform.Axis.Horizontal, 3.0f);
	canvasObject.GetComponent<RectTransform>().SetSizeWithCurrentAnchors(RectTransform.Axis.Vertical, 3.0f);

	return canvasObject;

}