using UnityEngine;
using System.Collections.Generic;
using System.Drawing;
using System.Drawing.Imaging;
/*
 这里引用的System.Drawing是在C:\Program Files (x86)\Unity\Editor\Data\Mono\lib\mono\2.0目录下，这个是unity安装的目录;
 */
public class GiftToTexture : MonoBehaviour
{
    public UITexture GifTexture;
    private List<Texture2D> _mTexture2Ds = new List<Texture2D>();
    private float _mTime;
    private float _mSpeed = 5.0f;
    // Use this for initialization
    void Start()
    {
        string path = Application.dataPath;
        Image image = Image.FromFile(path+@"/texture.gif");
        _mTexture2Ds = GifToTextureByCS(image);
    }

    // Update is called once per frame
    void Update()
    {
        if (null != GifTexture && _mTexture2Ds.Count > 0)
        {
            _mTime += Time.deltaTime;
            int index = (int)(_mTime * _mSpeed) % _mTexture2Ds.Count;
            GifTexture.mainTexture = _mTexture2Ds[index];
        }
    }

    List<Texture2D> GifToTextureByCS(Image image)
    {
        List<Texture2D> texture2D = null;
        if (null != image)
        {
            texture2D = new List<Texture2D>();
            //Debug.LogError(image.FrameDimensionsList.Length);
            //image.FrameDimensionsList.Length = 1;
            //根据指定的唯一标识创建一个提供获取图形框架维度信息的实例;
            FrameDimension frameDimension = new FrameDimension(image.FrameDimensionsList[0]);
            //获取指定维度的帧数;
            int framCount = image.GetFrameCount(frameDimension);
            for (int i = 0; i < framCount; i++)
            {
                //选择由维度和索引指定的帧;
                image.SelectActiveFrame(frameDimension, i);
                var framBitmap = new Bitmap(image.Width, image.Height);
                //从指定的Image 创建新的Graphics,并在指定的位置使用原始物理大小绘制指定的 Image;
                //将当前激活帧的图形绘制到framBitmap上;
                System.Drawing.Graphics.FromImage(framBitmap).DrawImage(image, Point.Empty);
                var frameTexture2D = new Texture2D(framBitmap.Width, framBitmap.Height);
                for (int x = 0; x < framBitmap.Width; x++)
                {
                    for (int y = 0; y < framBitmap.Height; y++)
                    {
                        //获取当前帧图片像素的颜色信息;
                        System.Drawing.Color sourceColor = framBitmap.GetPixel(x, y);
                        //设置Texture2D上对应像素的颜色信息;
                        frameTexture2D.SetPixel(x, framBitmap.Height - 1 - y, new Color32(sourceColor.R, sourceColor.G, sourceColor.B, sourceColor.A));
                    }
                }
                frameTexture2D.Apply();
                texture2D.Add(frameTexture2D);
            }
        }
        return texture2D;
    }
}

System.Drawing.dll放在Plugins文件夹下即可