public FrameGraphicController(byte[] bytes, ref int byteIndex)
{
//扩展标引导记 0x21 (1 byte)
Introducer = bytes[byteIndex];
byteIndex++;
//绘图控制扩展标记 0xF9 (1 byte)
Label = bytes[byteIndex];
byteIndex++;
//扩展字节长度 0x04 (1 byte)
Length = bytes[byteIndex];
byteIndex++;
#region Packet Fields (1byte)
//保留字段（3bit）
Reserved = bytes[byteIndex] >> 5;
//图像显示方法 (3 bit)
NextFrameDisposalMethod = (NextFrameDisposalMethod)((bytes[byteIndex] >> 2) % 8);
//用户输入标志 (1 bit)
FlagUserInput = (bytes[byteIndex] >> 1) % 2 == 1;
//透明颜色索引有效标志 (1 bit)
FlagTransparentColor = bytes[byteIndex] % 2 == 1;
#endregion
//指针下移
byteIndex++;
//帧延时 (2 byte)
DelayTime = BitConverter.ToUInt16(bytes, byteIndex);
byteIndex += 2;
//透明颜色索引 (1 byte)
TransparentColorIndex = bytes[byteIndex];
byteIndex++;
//结尾标识 (1 byte)
Terminator = bytes[byteIndex];
byteIndex++;
}
public static SequenceFrame[] GetFrames(TextAsset gifAsset)
{
try
{
if (_cache.ContainsKey(gifAsset.name))
{
return(_cache[gifAsset.name]);
}
var startTime = DateTime.Now;
//初始化GIF
var gif = new GraphicsInterchangeFormat(gifAsset.bytes);
//序列帧集初始化
var frames = new SequenceFrame[gif.FrameImageDescriptors.Length];
//初始化Texture
var frameTexture = new Texture2D(gif.Width, gif.Height);
//透明背景
var transparentPixels = frameTexture.GetPixels32();
for (var index = 0; index < transparentPixels.Length; index++)
{
transparentPixels[index] = Color.clear;
}
//背景色
var backgroundColor = gif.GetColor32(gif.BgColorIndex);
var backgroundPixels = frameTexture.GetPixels32();
for (var index = 0; index < backgroundPixels.Length; index++)
{
backgroundPixels[index] = backgroundColor;
}
//记录下一帧的处理方法
NextFrameDisposalMethod frameDisposalMethod = NextFrameDisposalMethod.Normal;
bool previousReserved = false;
//处理每个图块
for (var frameIndex = 0; frameIndex < frames.Length; frameIndex++)
{
//命名
frameTexture.name = "FrameOfIndex" + frameIndex;
//图像描述器
var frameImageDescriptor = gif.FrameImageDescriptors[frameIndex];
//绘图控制扩展
var frameGraphicController = gif.FrameGraphicControllers[frameIndex];
//上一帧控制器如果记录本帧的处理方法为bg，并且本帧的透明标识为true，那么背景替换为透明
if (frameDisposalMethod == NextFrameDisposalMethod.Bg && frameGraphicController.FlagTransparentColor)
{
//hack SetPixels is slower than SetPixels32
frameTexture.SetPixels32(transparentPixels);
}
//着色范围
var blockWidth = frameImageDescriptor.Width;
var blockHeight = frameImageDescriptor.Height;
var leftIndex = frameImageDescriptor.MarginLeft; //含
var rightBorder = leftIndex + blockWidth; //不含
var topBorder = gif.Height - frameImageDescriptor.MarginTop; //不含
var bottomIndex = topBorder - blockHeight; //含
//色表
var descriptorColors = frameImageDescriptor.GetColors32(frameGraphicController, gif);
//色表指针
var colorIndex = -1;
//gif的y是从上往下，texture的y是从下往上
for (var y = topBorder - 1; y >= bottomIndex; y--)
{
for (var x = leftIndex; x < rightBorder; x++)
{
colorIndex++;
//判断是否保留像素
if (previousReserved && descriptorColors[colorIndex].a == 0)
{
continue;
}
frameTexture.SetPixel(x, y, descriptorColors[colorIndex]);
}
}
//保存
frameTexture.wrapMode = TextureWrapMode.Clamp;
frameTexture.Apply();
//添加序列帧,并兵初始化Texture
var spriteFrame = frameTexture.GetSprite();
frames[frameIndex] = new SequenceFrame(spriteFrame, frameGraphicController.DelaySecond);
frameTexture = new Texture2D(gif.Width, gif.Height);
//预处理下一帧图像
previousReserved = false;
switch (frameGraphicController.NextFrameDisposalMethod)
{
//1 - Do not dispose. The graphic is to be left in place.
//保留此帧
case NextFrameDisposalMethod.Last:
frameTexture.SetPixels32(frames[frameIndex].Texture.GetPixels32());
previousReserved = true;
break;
//2 - Restore to background color. The area used by the graphic must be restored to the background color.
//还原成背景色
case NextFrameDisposalMethod.Bg:
frameTexture.SetPixels32(backgroundPixels);
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.
//还原成上一帧
case NextFrameDisposalMethod.Previous:
frameTexture.SetPixels32(frames[frameIndex - 1].Texture.GetPixels32());
previousReserved = true;
break;
}
frameDisposalMethod = frameGraphicController.NextFrameDisposalMethod;
}
Debug.Log(string.Format("Analyzing gif {0} with {1} frames costs {2} seconds ", gifAsset.name, frames.Length,
(DateTime.Now - startTime).TotalSeconds.ToString("0.000")));
_cache.Add(gifAsset.name, frames);
return(frames);
}
catch (Exception ex)
{
var logBuilder = new StringBuilder();
logBuilder.AppendLine("GIF解析发生错误/Gif analysed error");
logBuilder.AppendLine("可能是版本不兼容导致，请用PhotoShop 存储为web所用格式GIF 后重试/Mybe the version invalid , try to convert it by photoshop web format gif");
logBuilder.Append(ex.Message);
Debug.LogError(logBuilder.ToString());
return(null);
}
}
