改变图片的透明度
float speed=0.2f;
float starttime;
void Start () {
starttime = Time.time;
}
void Update()
{
GUITexture.color.a = Mathf.Lerp (0, 1, (Time.time - starttime) * speed);
}
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图片自适应屏幕
Rect cur = Rect (-Screen.width * 0.5, -Screen.height * 0.5, Screen.width, Screen.height);
改变图片的透明度，图片自适应屏幕
原文：http://blog.csdn.net/haifeng619/article/details/45918231
