[Unity基础]RenderTexture

参考链接：

https://www.cnblogs.com/Jimm/p/5951362.html

一.相关API

1.Texture2D.ReadPixels

从RenderTexture.active中复制像素，以左下角为原点。

2.MonoBehaviour.OnPostRender

当相机渲染完所有物体就会调用该方法，并且只有当这个脚本挂在相机时才会调用。

二.测试

新建一个场景，新建一个camera和一个go，把go设置为一个单独的层，让camera单独照这个层，主camera不要照这个层。调整camera的深度和targetTexture。

using UnityEngine;
using System.Collections;
using UnityEngine.UI;
using System.IO;

public class TestRenderTexture : MonoBehaviour {

    public Camera camera;
    public RawImage rawImage;
    bool isScreenShot = false;

    void Update()
    {
        //将镜头的画面保存到本地
        if (Input.GetKeyDown(KeyCode.Q))
        {
            Texture2D tex = RenderTexture2Texture2D(camera.targetTexture);

            //展示
            rawImage.texture = tex;

            //保存到本地
            byte[] bytes = tex.EncodeToPNG();
            File.WriteAllBytes(Application.dataPath + "/RenderTexture/Test.png", bytes);
            UnityEditor.AssetDatabase.Refresh();
        }

        //屏幕截图(方法1)
        if (Input.GetKeyDown(KeyCode.W))
        {
            StartCoroutine(ScreenShotIEnumerator());
        }

        //屏幕截图(方法2)
        if (Input.GetKeyDown(KeyCode.E))
        {
            isScreenShot = true;
        }
    }

    public IEnumerator ScreenShotIEnumerator()
    {
        yield return new WaitForEndOfFrame();
        rawImage.texture = ScreenShot();
    }

    private void OnPostRender()
    {
        //Debug.Log("OnPostRender");
        if (isScreenShot)
        {
            isScreenShot = false;
            rawImage.texture = ScreenShot();
        }
    }

    //屏幕截图
    public Texture2D ScreenShot()
    {
        Texture2D tex = new Texture2D(Screen.width, Screen.height, TextureFormat.ARGB32, false);
        tex.ReadPixels(new Rect(0, 0, Screen.width, Screen.height), 0, 0);
        tex.Apply();
        return tex;
    }

    //RenderTexture转Texture2D
    public Texture2D RenderTexture2Texture2D(RenderTexture rt)
    {
        RenderTexture preRT = RenderTexture.active;
        RenderTexture.active = rt;
        Texture2D tex = new Texture2D(rt.width, rt.height, TextureFormat.ARGB32, false);
        tex.ReadPixels(new Rect(0, 0, rt.width, rt.height), 0, 0);
        tex.Apply();
        RenderTexture.active = preRT;
        return tex;
    }
}