= =找不到難點拿出來說，直接看程式碼吧

using UnityEngine;
using System.Collections;
using System;

public static class Screenshot
{
    #region 全屏截圖
    public static IEnumerator CaptureScreen(string savaPath)
    {
        return CaptureScreen(new Rect(0, 0, Screen.width, Screen.height), savaPath);
    }

    public static IEnumerator CaptureScreen(Action<Texture2D> callback)
    {
        return CaptureScreen(new Rect(0, 0, Screen.width, Screen.height), callback);
    }

    public static void CaptureScreen(Camera camera, string savaPath)
    {
         CaptureScreen(camera,new Rect(0, 0, Screen.width, Screen.height), savaPath);
    }

    public static void CaptureScreen(Camera camera, Action<Texture2D> callback)
    {
         CaptureScreen(camera,new Rect(0, 0, Screen.width, Screen.height), callback);
    }
    #endregion

    /// <summary>
    /// 截圖指定區域，包括該區域所有物件
    /// </summary>
    /// <param name="rect"></param>
    /// <param name="savaPath"></param>
    /// <returns></returns>
    public static IEnumerator CaptureScreen(Rect rect, string savaPath)
    {
        yield return new WaitForEndOfFrame();
        Texture2D screenShot = new Texture2D((int)rect.width, (int)rect.height, TextureFormat.RGB24, false);
        screenShot.ReadPixels(rect, 0, 0, false);
        screenShot.Apply();

        byte[] bytes = screenShot.EncodeToPNG();
        System.IO.File.WriteAllBytes(savaPath, bytes);
        Texture2D.Destroy(screenShot);
        bytes = null;
    }

    public static IEnumerator CaptureScreen(Rect rect, Action<Texture2D> callback)
    {
        yield return new WaitForEndOfFrame();
        Texture2D screenShot = new Texture2D((int)rect.width, (int)rect.height, TextureFormat.RGB24, false);
        screenShot.ReadPixels(rect, 0, 0, false);
        screenShot.Apply();
        callback(screenShot);
    }

    /// <summary>
    /// 截圖指定相機的指定區域，只會獲得該相機的畫素[不包括相機的渲染]
    /// </summary>
    /// <param name="c"></param>
    /// <param name="r"></param>
    /// <param name="savePath"></param>
    public static void CaptureScreen(Camera c, Rect r, string savePath)
    {

        RenderTexture rt = new RenderTexture((int)r.width, (int)r.height, 0);
        c.targetTexture = rt;
        c.Render();

        RenderTexture.active = rt;
        Texture2D screenShot = new Texture2D((int)r.width, (int)r.height, TextureFormat.RGB24, false);
        screenShot.ReadPixels(r, 0, 0);
        screenShot.Apply();

        c.targetTexture = null;
        RenderTexture.active = null;
        GameObject.Destroy(rt);

        byte[] bytes = screenShot.EncodeToPNG();
        System.IO.File.WriteAllBytes(savePath, bytes);
        GameObject.Destroy(screenShot);
    }

    public static void CaptureScreen(Camera c, Rect r, Action<Texture2D> callback)
    {

        RenderTexture rt = new RenderTexture((int)r.width, (int)r.height, 0);
        c.targetTexture = rt;
        c.Render();

        RenderTexture.active = rt;
        Texture2D screenShot = new Texture2D((int)r.width, (int)r.height, TextureFormat.RGB24, false);
        screenShot.ReadPixels(r, 0, 0);
        screenShot.Apply();

        c.targetTexture = null;
        RenderTexture.active = null;
        GameObject.Destroy(rt);

        callback(screenShot);
    }
}