using UnityEngine;
using UnityEditor;
using System;
using System.IO;
using System.Collections;
using System.Collections.Generic;
 
public class ParticleExporter : MonoBehaviour
{
 // Default folder name where you want the animations to be output
 public string folder = "PNG_Animations";
 
 // Framerate at which you want to play the animation
 public int frameRate = 25;     // export frame rate 导出帧率，设置Time.captureFramerate会忽略真实时间，直接使用此帧率
 public float frameCount = 100;    // export frame count 导出帧的数目，100帧则相当于导出5秒钟的光效时间。由于导出每一帧的时间很长，所以导出时间会远远长于直观的光效播放时间
 public int screenWidth = 960;    // not use 暂时没用，希望可以直接设置屏幕的大小（即光效画布的大小）
 public int screenHeight = 640;
 public Vector3 cameraPosition = Vector3.zero;
 public Vector3 cameraRotation = Vector3.zero;
 
 private string realFolder = ""; // real folder where the output files will be
 private float originaltimescaleTime; // track the original time scale so we can freeze the animation between frames
 private float currentTime = 0;
 private bool over = false;
 private int currentIndex = 0;
 private Camera exportCamera; // camera for export 导出光效的摄像机，使用RenderTexture
 
 public void Start()
 {
  // set frame rate
  Time.captureFramerate = frameRate;
 
  // Create a folder that doesn't exist yet. Append number if necessary.
  realFolder = Path.Combine(folder, name);
 
  // Create the folder
  if (!Directory.Exists(realFolder)) {
   Directory.CreateDirectory(realFolder);
  }
 
  originaltimescaleTime = Time.timeScale;
 
  GameObject goCamera = Camera.main.gameObject;
  if (cameraPosition != Vector3.zero) {
   goCamera.transform.position = cameraPosition;
  }
 
  if (cameraRotation != Vector3.zero) {
   goCamera.transform.rotation = Quaternion.Euler(cameraRotation);
  }
 
  GameObject go = Instantiate(goCamera) as GameObject;
  exportCamera = go.GetComponent<Camera>();
 
  currentTime = 0;
 
  
 }
 
 void Update()
 {
  currentTime += Time.deltaTime;
  if (!over && currentIndex >= frameCount) {
   over = true;
   Cleanup();
   Debug.Log("Finish");
   return;
  }
 
  // 每帧截屏
  StartCoroutine(CaptureFrame());
 }
 
 void Cleanup()
 {
  DestroyImmediate(exportCamera);
  DestroyImmediate(gameObject);
 }
 
 IEnumerator CaptureFrame()
 {
  // Stop time
  Time.timeScale = 0;
  // Yield to next frame and then start the rendering
  // this is important, otherwise will have error
  yield return new WaitForEndOfFrame();
 
  string filename = String.Format("{0}/{1:D04}.png", realFolder, ++currentIndex);
  Debug.Log(filename);
 
  int width = Screen.width;
  int height = Screen.height;
 
  //Initialize and render textures
  RenderTexture blackCamRenderTexture = new RenderTexture(width, height, 24, RenderTextureFormat.ARGB32);
  RenderTexture whiteCamRenderTexture = new RenderTexture(width, height, 24, RenderTextureFormat.ARGB32);
 
  exportCamera.targetTexture = blackCamRenderTexture;
  exportCamera.backgroundColor = Color.black;
  exportCamera.Render();
  RenderTexture.active = blackCamRenderTexture;
  Texture2D texb = GetTex2D();
 
  //Now do it for Alpha Camera
  exportCamera.targetTexture = whiteCamRenderTexture;
  exportCamera.backgroundColor = Color.white;
  exportCamera.Render();
  RenderTexture.active = whiteCamRenderTexture;
  Texture2D texw = GetTex2D();
 
  // If we have both textures then create final output texture
  if (texw && texb) {
   Texture2D outputtex = new Texture2D(width, height, TextureFormat.ARGB32, false);
 
   // we need to check alpha ourselves,because particle use additive shader
   // Create Alpha from the difference between black and white camera renders
   for (int y = 0; y < outputtex.height; ++y) { // each row
    for (int x = 0; x < outputtex.width; ++x) { // each column
     float alpha;
     alpha = texw.GetPixel(x, y).r - texb.GetPixel(x, y).r;
     alpha = 1.0f - alpha;
     Color color;
     if (alpha == 0) {
      color = Color.clear;
     } else {
      color = texb.GetPixel(x, y);
     }
     color.a = alpha;
     outputtex.SetPixel(x, y, color);
    }
   }
 
 
   // Encode the resulting output texture to a byte array then write to the file
   byte[] pngShot = outputtex.EncodeToPNG();
   File.WriteAllBytes(filename, pngShot);
 
   // cleanup, otherwise will memory leak
   pngShot = null;
   RenderTexture.active = null;
   DestroyImmediate(outputtex);
   outputtex = null;
   DestroyImmediate(blackCamRenderTexture);
   blackCamRenderTexture = null;
   DestroyImmediate(whiteCamRenderTexture);
   whiteCamRenderTexture = null;
   DestroyImmediate(texb);
   texb = null;
   DestroyImmediate(texw);
   texb = null;
 
   System.GC.Collect();
 
   // Reset the time scale, then move on to the next frame.
   Time.timeScale = originaltimescaleTime;
  }
 }
 
 // Get the texture from the screen, render all or only half of the camera
 private Texture2D GetTex2D()
 {
  // Create a texture the size of the screen, RGB24 format
  int width = Screen.width;
  int height = Screen.height;
  Texture2D tex = new Texture2D(width, height, TextureFormat.ARGB32, false);
  // Read screen contents into the texture
  tex.ReadPixels(new Rect(0, 0, width, height), 0, 0);
  tex.Apply();
  return tex;
 }
}