using System.Collections.Generic;
using System.Drawing;
using System.Drawing.Imaging;
 
using UnityEngine;
 
public class AnimatedGifDrawer : MonoBehaviour
{
    public string loadingGifPath;//路徑
    public UITexture tex;//圖片
    public float speed = 0.1f;//播放速度
 
    private bool isPlay = false;//是否播放
    private int i = 0;//控制要播放的圖片
 
    private List<Texture2D> gifFrames = new List<Texture2D>();//存儲解析出來的圖片
    void Awake()
    {
        Image gifImage = Image.FromFile(loadingGifPath);
        FrameDimension dimension = new FrameDimension(gifImage.FrameDimensionsList[0]);
        int frameCount = gifImage.GetFrameCount(dimension);
        for (int i = 0; i < frameCount; i++)
        {
            gifImage.SelectActiveFrame(dimension, i);
            Bitmap frame = new Bitmap(gifImage.Width, gifImage.Height);
            System.Drawing.Graphics.FromImage(frame).DrawImage(gifImage, Point.Empty);
            Texture2D frameTexture = new Texture2D(frame.Width, frame.Height);
            for (int x = 0; x < frame.Width; x++)
                for (int y = 0; y < frame.Height; y++)
                {
                    System.Drawing.Color sourceColor = frame.GetPixel(x, y);
                    frameTexture.SetPixel( x, frame.Height - 1 - y, new Color32(sourceColor.R, sourceColor.G, sourceColor.B, sourceColor.A)); // for some reason, x is flipped
                }
            frameTexture.Apply();
            gifFrames.Add(frameTexture);
        }
    }
 
    private void Update()
    {
        if (isPlay == true)
        {
            i++;
            tex.mainTexture = gifFrames[(int)(i * speed) % gifFrames.Count];
        }    
    }
 
    /// <summary>
    /// 播放動畫
    /// </summary>
    public void StartAni()
    {
        isPlay = true;
    }
 
    /// <summary>
    /// 停止動畫
    /// </summary>
    public void StopAni()
    {
        isPlay = false;
        i = 0;
    }
}

//處理每個圖塊
            for (int index = 0; index < gif.GraphicControlExtensions.Count; index++)
            {
                //命名
                textureDescriptor.name = "Frame" + (index + 1);
 
                //圖像描述器
                ImageDescriptor imageDescriptor = gif.ImageDescriptors[index];
 
                //像素色號集
                byte[] colorIndexs = imageDescriptor.GetColorIndexs();
 
                //繪圖控制擴展
                GraphicControlExtension control = gif.GraphicControlExtensions[index];
 
                //像素指針
                int pixelIndex = 0;
 
                //gif的像素點順序 左上到右下,unity的像素順序是 左下到右上,所以y套x, y翻轉(zhuǎn)一下
                for (int y = imageDescriptor.MarginTop; y < imageDescriptor.MarginTop + imageDescriptor.Height; y++)
                {
                    for (int x = imageDescriptor.MarginLeft; x < imageDescriptor.MarginLeft + imageDescriptor.Width; x++)
                    {
                        Color32 colorPixel = imageDescriptor.GetColor(colorIndexs[pixelIndex++], control, gif);
                        if (colorPixel.a == 0 && reserve)
                            continue;
                        textureDescriptor.SetPixel(x, gif.Height - y - 1, colorPixel);
                    }
                }
 
                //保存
                textureDescriptor.Apply();
 
                //添加序列幀
                Sprite sprite = Sprite.Create(textureDescriptor, new Rect(0, 0, textureDescriptor.width, textureDescriptor.height), Vector2.zero);
                sprite.name = textureDescriptor.name;
                frames.Add(new UnityFrame(sprite, control.DelaySecond));
 
                //初始化圖像
                textureDescriptor = new Texture2D(gif.Width, gif.Height);
                reserve = false;
 
                //下一幀圖像預(yù)處理
                switch (control.DisposalMethod)
                {
                    //1 - Do not dispose. The graphic is to be left in place. //保留此幀
                    case DisposalMethod.Last:
                        textureDescriptor.SetPixels(frames[index].Texture.GetPixels());
                        reserve = true;
                        break;
 
                    //2 - Restore to background color. The area used by the graphic must be restored to the background color. //還原成背景色
                    case DisposalMethod.Bg:
                        textureDescriptor.SetPixels(textureBg.GetPixels());
                        break;
 
                    //3 - Restore to previous. The decoder is required to restore the area overwritten by the graphic with what was there prior to rendering the graphic.//還原成上一幀
                    case DisposalMethod.Previous:
                        textureDescriptor.SetPixels(frames[index - 1].Texture.GetPixels());
                        reserve = true;
                        break;
                }
            }

       /// <summary>
        /// 遞歸播放
        /// </summary>
        /// <returns></returns>
        IEnumerator Play()
        {
            if (mStop)
            {
                mFrameIndex = 0;
                yield break;
            }
 
            //幀序號
            mFrameIndex = mFrameIndex % mFrames.Count;
            //繪圖
            if (mRawImage)
                mRawImage.texture = mFrames[mFrameIndex].Texture;
            if (mImage)
                mImage.sprite = mFrames[mFrameIndex].Sprite;
            //幀延時
            yield return new WaitForSeconds(mFrames[mFrameIndex].DelaySecond);
            //序號++
            mFrameIndex++;
 
            //播放一次
            if (!Loop && mFrameIndex == mFrames.Count)
                yield break;
 
            //遞歸播放下一幀
            StartCoroutine(Play());
        }