unity中全屏背景图缩放

 using UnityEngine;
 using System.Collections;

 public class BgPicScript : MonoBehaviour {

     // Use this for initialization
     public UITexture bg;
     void Start () {

         Debug.Log("device宽高: " + Screen.width + "_" + Screen.height);

         UIRoot root = GameObject.FindObjectOfType<UIRoot>();

         if (root != null)
         {
             //终极大杀器 整体资源缩放比例
             float s = (float)root.activeHeight / Screen.height;
             int height =  Mathf.CeilToInt(Screen.height * s);
             int width = Mathf.CeilToInt(Screen.width * s);

             Debug.Log("按设计分辨率屏幕width = " + width + "_height = " + height);

             Debug.Log("背景图片的设计分辨率bgWIdth:" + bg.width + "_bgHeight:" + bg.height);

             float bgRatio = (float) bg.width / bg.height;
             float manualRatio = (float)width / height;

             if (bgRatio < manualRatio) //遇到按照屏幕高度缩放水平两边出现黑边的情况,要按照宽度来缩放背景图片
             {
                 //bg.width = width;
                 //bg.height = Mathf.CeilToInt(width / );

                 float targetScale = (float)width / bg.width;
                 bg.transform.localScale = new Vector3(targetScale,targetScale, );
             }
         }

     }

     // Update is called once per frame
     void Update () {

     }
 }

 using UnityEngine;
 using System.Collections;

 public class UIRootScript : MonoBehaviour {

     // Use this for initialization
     void Start () {
         AdaptiveUI();
     }

     // Update is called once per frame
     void Update () {

     }

     static private void AdaptiveUI()
     {
         int ManualWidth = ;
         int ManualHeight = ;
         UIRoot uiRoot = GameObject.FindObjectOfType<UIRoot>();
         if (uiRoot != null)
         {
             if (System.Convert.ToSingle(Screen.height) / Screen.width > System.Convert.ToSingle(ManualHeight) / ManualWidth)
                 uiRoot.manualHeight = Mathf.RoundToInt(System.Convert.ToSingle(ManualWidth) / Screen.width * Screen.height);
             else
                 uiRoot.manualHeight = ManualHeight;
         }
         Debug.Log("uiRoot Height:" + uiRoot.manualHeight);
     }
 }