Unity实现背景图片淡入淡出效果

using UnityEngine;
using System.Collections;
using UnityEngine.UI;
 
public class BgFadeInOut : MonoBehaviour
{
 public Image bgimages;
 public float showTime = 10;
 public float ShowTimeTrigger = 0;
 public float fadeTime = 3;
 public float fadeTimeTrigger = 0;
 private bool show=true;
 // Use this for initialization
 void Start()
 {
 
 }
 // Update is called once per frame
 void Update()
 {
 ShowTimeTrigger += Time.deltaTime; 
 if (ShowTimeTrigger > showTime)
 {
  if (fadeTimeTrigger >= 0 && fadeTimeTrigger < fadeTime)
  {
  fadeTimeTrigger += Time.deltaTime;
  if(show)
  {
   bgimages.color = new Color(1, 1, 1, 1 - (fadeTimeTrigger / fadeTime));
 
  }
  else
  {
   bgimages.color = new Color(1, 1, 1, (fadeTimeTrigger / fadeTime));
 
  }
  }
  else
  {
  fadeTimeTrigger = 0;
  ShowTimeTrigger = 0;
  if(show)
  {
   show = false;
  }
  else
  {
   show = true;
  }
  }
 }  
 
 }
}