using System.Linq;
using UnityEngine;

/// <summary>
/// 畫板
/// </summary>
public class Board : MonoBehaviour
{
 //當畫筆移動速度很快時，為了不出現(xiàn)斷斷續(xù)續(xù)的點，所以需要對兩個點之間進行插值，lerp就是插值系數(shù)
 [Range(0, 1)]
 public float lerp = 0.05f;
 //初始化背景的圖片
 public Texture2D initailizeTexture;
 //當前背景的圖片
 private Texture2D currentTexture;
 //畫筆所在位置映射到畫板圖片的UV坐標
 private Vector2 paintPos;

 private bool isDrawing = false;//當前畫筆是不是正在畫板上
 //離開時畫筆所在的位置 
 private int lastPaintX;
 private int lastPaintY;
 //畫筆所代表的色塊的大小
 private int painterTipsWidth = 30;
 private int painterTipsHeight = 15;
 //當前畫板的背景圖片的尺寸
 private int textureWidth;
 private int textureHeight;

 //畫筆的顏色
 private Color32[] painterColor;

 private Color32[] currentColor;
 private Color32[] originColor;


 private void Start()
 {
 //獲取原始圖片的大小 
 Texture2D originTexture = GetComponent<MeshRenderer>().material.mainTexture as Texture2D;
 textureWidth = originTexture.width;//1920 
 textureHeight = originTexture.height;//1080

 //設置當前圖片
 currentTexture = new Texture2D(textureWidth, textureHeight, TextureFormat.RGBA32, false, true);
 currentTexture.SetPixels32(originTexture.GetPixels32());
 currentTexture.Apply();

 //賦值給黑板
 GetComponent<MeshRenderer>().material.mainTexture = currentTexture;

 //初始化畫筆的顏色
 painterColor = Enumerable.Repeat<Color32>(new Color32(255, 0, 0, 255), painterTipsWidth * painterTipsHeight).ToArray<Color32>();
 }

 private void LateUpdate()
 {
 //計算當前畫筆，所代表的色塊的一個起始點
 int texPosX = (int)(paintPos.x * (float)textureWidth - (float)(painterTipsWidth / 2));
 int texPosY = (int)(paintPos.y * (float)textureHeight - (float)(painterTipsHeight / 2));
 if (isDrawing)
 {
  //改變畫筆所在的塊的像素值
  currentTexture.SetPixels32(texPosX, texPosY, painterTipsWidth, painterTipsHeight, painterColor);
  //如果快速移動畫筆的話，會出現(xiàn)斷續(xù)的現(xiàn)象，所以要插值
  if (lastPaintX != 0 && lastPaintY != 0)
  {
  int lerpCount = (int)(1 / lerp);
  for (int i = 0; i <= lerpCount; i++)
  {
   int x = (int)Mathf.Lerp((float)lastPaintX, (float)texPosX, lerp);
   int y = (int)Mathf.Lerp((float)lastPaintY, (float)texPosY, lerp);
   currentTexture.SetPixels32(x, y, painterTipsWidth, painterTipsHeight, painterColor);
  }
  }
  currentTexture.Apply();
  lastPaintX = texPosX;
  lastPaintY = texPosY;
 }
 else
 {
  lastPaintX = lastPaintY = 0;
 }

 }

 /// <summary>
 /// 設置當前畫筆所在的UV位置
 /// </summary>
 /// <param name="x"></param>
 /// <param name="y"></param>
 public void SetPainterPositon(float x, float y)
 {
 paintPos.Set(x, y);
 }

 /// <summary>
 /// 畫筆當前是不是在畫畫
 /// </summary>
 public bool IsDrawing
 {
 get
 {
  return isDrawing;
 }
 set
 {
  isDrawing = value;
 }
 }

 /// <summary>
 /// 使用當前正在畫板上的畫筆的顏色
 /// </summary>
 /// <param name="color"></param>
 public void SetPainterColor(Color32 color)
 {
 if (!painterColor[0].IsEqual(color))
 {
  for (int i = 0; i < painterColor.Length; i++)
  {
  painterColor[i] = color;
  }
 }
 }


}
public static class MethodExtention
{
 /// <summary>
 /// 用于比較兩個Color32類型是不是同種顏色
 /// </summary>
 /// <param name="origin"></param>
 /// <param name="compare"></param>
 /// <returns></returns>
 public static bool IsEqual(this Color32 origin, Color32 compare)
 {
 if (origin.g == compare.g && origin.r == compare.r)
 {
  if (origin.a == compare.a && origin.b == compare.b)
  {
  return true;
  }
 }
 return false;
 }
}

using UnityEngine;

public class Painter : MonoBehaviour
{
 /// <summary>
 /// 畫筆的顏色
 /// </summary>
 public Color32 penColor;

 public Transform rayOrigin;

 private RaycastHit hitInfo;
 //這個畫筆是不是正在被手柄抓著
 private bool IsGrabbing;
 private static Board board;//設置成類型的成員，而不是類型實例的成員，因為所有畫筆都是用的同一個board

 private void Start()
 {
 //將畫筆部件設置為畫筆的顏色，用于識別這個畫筆的顏色
 foreach (var renderer in GetComponentsInChildren<MeshRenderer>())
 {
  if (renderer.transform == transform)
  {
  continue;
  }
  renderer.material.color = penColor;
 }
 if (!board)
 {
  board = FindObjectOfType<Board>();
 }
 
 }

 private void Update()
 {
 Ray r = new Ray(rayOrigin.position, rayOrigin.forward);
 if (Physics.Raycast(r, out hitInfo, 0.1f))
 {
  if (hitInfo.collider.tag == "Board")
  {
  //設置畫筆所在位置對應畫板圖片的UV坐標 
  board.SetPainterPositon(hitInfo.textureCoord.x, hitInfo.textureCoord.y);
  //當前筆的顏色
  board.SetPainterColor(penColor);
  board.IsDrawing = true;
  IsGrabbing = true;
  }
 }
 else if(IsGrabbing)
 {
  board.IsDrawing = false;
  IsGrabbing = false;
 }
 }

}