/common/src/core/Utils/Image/GifImage.cs

using System;

using System.Collections;

using System.Collections.Generic;

using System.Collections.Specialized;

using System.Drawing;

using System.Drawing.Imaging;

using System.IO;



namespace VVVV.Utils.Imaging

{

    //adapted from:

    //http://stackoverflow.com/questions/1196322/how-to-create-an-animated-gif-in-net

    //gif file format specification:

    //http://www.fileformat.info/format/gif/egff.htm



    /// <summary>

    /// Uses default .net GIF encoding and adds animation headers.

    /// </summary>

    public class Gif : IDisposable, IEnumerable<Image>

    {

        #region Header Constants

        const byte FileTrailer = 0x3b,

            ApplicationBlockSize = 0x0b,

            GraphicControlExtensionBlockSize = 0x04;



        const int ApplicationExtensionBlockIdentifier = 0xff21,

            GraphicControlExtensionBlockIdentifier = 0xf921;



        const long SourceGlobalColorInfoPosition = 10,

            SourceGraphicControlExtensionLength = 8,

            SourceImageBlockHeaderLength = 11,

            SourceColorBlockPosition = 13;



        long SourceColorBlockLength, SourceGraphicControlExtensionPosition, SourceImageBlockPosition;



        const string NetscapeIdentification = "NETSCAPE2.0",

            VVVVIdentification = "vvvv50.....",

            FileType = "GIF",

            FileVersion = "89a";

        #endregion



        class GifFrame : IDisposable

        {

            public Image Image;

            public double Delay;

            public int XOffset, YOffset;



            public GifFrame(Image image, double delay, int xOffset, int yOffset)

            {

                Image = image;

                Delay = delay;

                XOffset = xOffset;

                YOffset = yOffset;

            }



            public void Dispose()

            {

                Image.Dispose();

            }

        }



        List<GifFrame> Frames = new List<GifFrame>();



        public Gif() { DefaultFrameDelay = 1; }



        public Gif(Stream InStream, int Repeat = 0, int Delay = 500)

        {

            using (var Animation = Bitmap.FromStream(InStream))

            {

                int Length = Animation.GetFrameCount(FrameDimension.Time);



                DefaultFrameDelay = Delay;

                this.Repeat = Repeat;



                for (int i = 0; i < Length; ++i)

                {

                    Animation.SelectActiveFrame(FrameDimension.Time, i);



                    var Frame = new Bitmap(Animation.Size.Width, Animation.Size.Height);



                    Graphics.FromImage(Frame).DrawImage(Animation, new Point(0, 0));



                    Frames.Add(new GifFrame(Frame, Delay, 0, 0));

                }

            }

        }



        #region Properties

        public int DefaultWidth { get; set; }



        public int DefaultHeight { get; set; }



        public int Count { get { return Frames.Count; } }



        /// <summary>

        /// Default Delay in Milliseconds

        /// </summary>

        public int DefaultFrameDelay { get; set; }



        public int Repeat { get; private set; }

        #endregion



        /// <summary>

        /// Adds a frame to this animation.

        /// </summary>

        /// <param name="Image">The image to add</param>

        /// <param name="XOffset">The positioning x offset this image should be displayed at.</param>

        /// <param name="YOffset">The positioning y offset this image should be displayed at.</param>

        public void AddFrame(Image Image, double? frameDelay = null, int XOffset = 0, int YOffset = 0)

        {

            Frames.Add(new GifFrame(Image, frameDelay ?? DefaultFrameDelay, XOffset, YOffset));

        }



        public void AddFrame(string FilePath, double? frameDelay = null, int XOffset = 0, int YOffset = 0)

        {

            AddFrame(new Bitmap(FilePath), frameDelay, XOffset, YOffset);

        }



        public void RemoveAt(int Index) { Frames.RemoveAt(Index); }



        public void Clear()

        {

            foreach (var frame in Frames)

                frame.Dispose();

            Frames.Clear();

        }



        public void Save(Stream OutStream, PaletteType paletteType, DitherType ditherType, int colorCount)

        {

            using (var Writer = new BinaryWriter(OutStream))

            {

                //Header

                Writer.Write(FileType.ToCharArray());

                Writer.Write(FileVersion.ToCharArray());



                //Logical Screen Descriptor

                var w = Frames[0].Image.Width;

                var h = Frames[0].Image.Height;

                Writer.Write((short)(DefaultWidth == 0 ? w : DefaultWidth)); // Initial Logical Width

                Writer.Write((short)(DefaultHeight == 0 ? h : DefaultHeight)); // Initial Logical Height

                

                byte gctInfo = 0;

                if (paletteType != PaletteType.Optimal) //use a global colortable

                {

                    using (var gifStream = new MemoryStream())

                    {

                        var bitmap = new Bitmap(Frames[0].Image);

                        bitmap.ChangeTo8bppIndexed(paletteType, ditherType, colorCount);

                        bitmap.Save(gifStream, ImageFormat.Gif);



                        gifStream.Position = SourceGlobalColorInfoPosition;

                        gctInfo = (byte)gifStream.ReadByte();

                        var bv = new BitVector32(gctInfo);

                        var sizeSection = BitVector32.CreateSection(7);

                        SourceColorBlockLength = (1 << (bv[sizeSection] + 1)) * 3;

                        SourceGraphicControlExtensionPosition = SourceColorBlockLength + 13;

                        SourceImageBlockPosition = SourceGraphicControlExtensionPosition;



                        Writer.Write(gctInfo); // Global Color Table Info

                        Writer.Write((byte)0); // Background Color Index

                        Writer.Write((byte)0); // Pixel aspect ratio



                        WriteColorTable(gifStream, Writer);

                    }

                }

                else //local colortables will be used for each frame

                {

                    Writer.Write(gctInfo); // Global Color Table Info

                    Writer.Write((byte)0); // Background Color Index

                    Writer.Write((byte)0); // Pixel aspect ratio

                }

                

                //Netscape extension for looping animations

                unchecked { Writer.Write((short)ApplicationExtensionBlockIdentifier); };

                Writer.Write((byte)ApplicationBlockSize);

                Writer.Write(NetscapeIdentification.ToCharArray());

                Writer.Write((byte)3); // Application block length

                Writer.Write((byte)1);

                Writer.Write((short)Repeat); // Repeat count for images.

                Writer.Write((byte)0); // terminator



                // vvvv Extension Header

                unchecked { Writer.Write((short)ApplicationExtensionBlockIdentifier); };

                Writer.Write((byte)ApplicationBlockSize);

                Writer.Write(VVVVIdentification.ToCharArray());

                Writer.Write((byte)1); // Application block length

                Writer.Write((byte)0); // dummy

                Writer.Write((byte)0); // terminator



                //individual frames

                for (int i = 0; i < Count; ++i)

                {

                    var frame = Frames[i];

                    {

                        using (var gifStream = new MemoryStream())

                        {

                            var bitmap = new Bitmap(frame.Image);

                            if (bitmap.ChangeTo8bppIndexed(paletteType, ditherType, colorCount) == 0)

                                bitmap.Save(gifStream, ImageFormat.Gif);

                            else

                                frame.Image.Save(gifStream, ImageFormat.Gif);



                            WriteGraphicControlBlock(gifStream, Writer, frame.Delay);

                            WriteImageBlock(gifStream, Writer, paletteType == PaletteType.Optimal, frame.XOffset, frame.YOffset, bitmap.Width, bitmap.Height);

                        }

                    }

                }



                // Complete File

                Writer.Write(FileTrailer);

            }

        }



        #region Write

        void WriteColorTable(Stream sourceGif, BinaryWriter Writer)

        {

            sourceGif.Position = SourceColorBlockPosition; // Locating the image color table

            var colorTable = new byte[SourceColorBlockLength]; 

            sourceGif.Read(colorTable, 0, colorTable.Length);

            Writer.Write(colorTable, 0, colorTable.Length);

        }



        void WriteGraphicControlBlock(Stream sourceGif, BinaryWriter Writer, double frameDelay)

        {

            unchecked { Writer.Write((short)GraphicControlExtensionBlockIdentifier); }; // Identifier

            Writer.Write((byte)GraphicControlExtensionBlockSize); // Block Size

            Writer.Write((byte)(0 & 0xf7 | 0x08)); // Setting disposal flag

            Writer.Write((short)(frameDelay)); // Setting frame delay

            Writer.Write((byte)0); // (byte)blockhead[6]); // Transparent color index

            Writer.Write((byte)0); // Terminator

        }



        void WriteImageBlock(Stream sourceGif, BinaryWriter Writer, bool includeColorTable, int x, int y, int w, int h)

        {

            sourceGif.Position = SourceGlobalColorInfoPosition;

            var gctInfo = (byte)sourceGif.ReadByte();

            var bv = new BitVector32(gctInfo);

            var sizeSection = BitVector32.CreateSection(7);

            SourceColorBlockLength = (1 << (bv[sizeSection] + 1)) * 3;

            SourceImageBlockPosition = SourceColorBlockLength + 13;



            sourceGif.Position = SourceImageBlockPosition; // Locating the image block

            var header = new byte[SourceImageBlockHeaderLength];

            sourceGif.Read(header, 0, header.Length);

            Writer.Write((byte)header[0]); // Separator

            Writer.Write((short)x); // Position X

            Writer.Write((short)y); // Position Y

            Writer.Write((short)w); // Width

            Writer.Write((short)h); // Height



            if (includeColorTable)

            {

                Writer.Write((byte)(gctInfo & 0x3f | 0x80)); // Enabling local color table

                WriteColorTable(sourceGif, Writer);

            }

            else

                Writer.Write((byte)0); // (header[9] & 0x07 | 0x07)); // Disabling local color table



            Writer.Write((byte)header[10]); // LZW Min Code Size



            // Read/Write image data

            sourceGif.Position = SourceImageBlockPosition + SourceImageBlockHeaderLength;



            var dataLength = sourceGif.ReadByte();

            while (dataLength > 0)

            {

                var imgData = new byte[dataLength];

                sourceGif.Read(imgData, 0, dataLength);



                Writer.Write((byte)dataLength);

                Writer.Write(imgData, 0, dataLength);

                dataLength = sourceGif.ReadByte();

            }



            Writer.Write((byte)0); // Terminator

        }

        #endregion



        public void Dispose()

        {

            Frames.Clear();

            Frames = null;

        }



        public Image this[int Index] { get { return Frames[Index].Image; } }



        public IEnumerator<Image> GetEnumerator() { foreach (var Frame in Frames) yield return Frame.Image; }



        IEnumerator IEnumerable.GetEnumerator() { return GetEnumerator(); }

    }

}