Embedded Tango.AnimatedGif !

17 files changed, 733 insertions, 0 deletions

diff --git a/Software/Visual_Studio/Tango.AnimatedGif/Decoding/GifApplicationExtension.cs b/Software/Visual_Studio/Tango.AnimatedGif/Decoding/GifApplicationExtension.cs
new file mode 100644
index 000000000..bbf8a5820
--- /dev/null
+++ b/Software/Visual_Studio/Tango.AnimatedGif/Decoding/GifApplicationExtension.cs
@@ -0,0 +1,50 @@
+using System;
+using System.IO;
+using System.Text;
+
+namespace Tango.AnimatedGif.Decoding
+{
+    // label 0xFF
+    internal class GifApplicationExtension : GifExtension
+    {
+        internal const int ExtensionLabel = 0xFF;
+
+        public int BlockSize { get; private set; }
+        public string ApplicationIdentifier { get; private set; }
+        public byte[] AuthenticationCode { get; private set; }
+        public byte[] Data { get; private set; }
+
+        private GifApplicationExtension()
+        {
+        }
+
+        internal override GifBlockKind Kind
+        {
+            get { return GifBlockKind.SpecialPurpose; }
+        }
+
+        internal static GifApplicationExtension ReadApplication(Stream stream)
+        {
+            var ext = new GifApplicationExtension();
+            ext.Read(stream);
+            return ext;
+        }
+
+        private void Read(Stream stream)
+        {
+            // Note: at this point, the label (0xFF) has already been read
+
+            byte[] bytes = new byte[12];
+            stream.ReadAll(bytes, 0, bytes.Length);
+            BlockSize = bytes[0]; // should always be 11
+            if (BlockSize != 11)
+                throw GifHelpers.InvalidBlockSizeException("Application Extension", 11, BlockSize);
+
+            ApplicationIdentifier = Encoding.ASCII.GetString(bytes, 1, 8);
+            byte[] authCode = new byte[3];
+            Array.Copy(bytes, 9, authCode, 0, 3);
+            AuthenticationCode = authCode;
+            Data = GifHelpers.ReadDataBlocks(stream, false);
+        }
+    }
+}
diff --git a/Software/Visual_Studio/Tango.AnimatedGif/Decoding/GifBlock.cs b/Software/Visual_Studio/Tango.AnimatedGif/Decoding/GifBlock.cs
new file mode 100644
index 000000000..331e7bd8f
--- /dev/null
+++ b/Software/Visual_Studio/Tango.AnimatedGif/Decoding/GifBlock.cs
@@ -0,0 +1,28 @@
+using System.Collections.Generic;
+using System.IO;
+
+namespace Tango.AnimatedGif.Decoding
+{
+    internal abstract class GifBlock
+    {
+        internal static GifBlock ReadBlock(Stream stream, IEnumerable<GifExtension> controlExtensions, bool metadataOnly)
+        {
+            int blockId = stream.ReadByte();
+            if (blockId < 0)
+                throw GifHelpers.UnexpectedEndOfStreamException();
+            switch (blockId)
+            {
+                case GifExtension.ExtensionIntroducer:
+                    return GifExtension.ReadExtension(stream, controlExtensions, metadataOnly);
+                case GifFrame.ImageSeparator:
+                    return GifFrame.ReadFrame(stream, controlExtensions, metadataOnly);
+                case GifTrailer.TrailerByte:
+                    return GifTrailer.ReadTrailer();
+                default:
+                    throw GifHelpers.UnknownBlockTypeException(blockId);
+            }
+        }
+
+        internal abstract GifBlockKind Kind { get; }
+    }
+}
diff --git a/Software/Visual_Studio/Tango.AnimatedGif/Decoding/GifBlockKind.cs b/Software/Visual_Studio/Tango.AnimatedGif/Decoding/GifBlockKind.cs
new file mode 100644
index 000000000..eab7ea2c1
--- /dev/null
+++ b/Software/Visual_Studio/Tango.AnimatedGif/Decoding/GifBlockKind.cs
@@ -0,0 +1,10 @@
+namespace Tango.AnimatedGif.Decoding
+{
+    internal enum GifBlockKind
+    {
+        Control,
+        GraphicRendering,
+        SpecialPurpose,
+        Other
+    }
+}
diff --git a/Software/Visual_Studio/Tango.AnimatedGif/Decoding/GifColor.cs b/Software/Visual_Studio/Tango.AnimatedGif/Decoding/GifColor.cs
new file mode 100644
index 000000000..8c0461941
--- /dev/null
+++ b/Software/Visual_Studio/Tango.AnimatedGif/Decoding/GifColor.cs
@@ -0,0 +1,25 @@
+namespace Tango.AnimatedGif.Decoding
+{
+    internal struct GifColor
+    {
+        private readonly byte _r;
+        private readonly byte _g;
+        private readonly byte _b;
+
+        internal GifColor(byte r, byte g, byte b)
+        {
+            _r = r;
+            _g = g;
+            _b = b;
+        }
+
+        public byte R { get { return _r; } }
+        public byte G { get { return _g; } }
+        public byte B { get { return _b; } }
+
+        public override string ToString()
+        {
+            return string.Format("#{0:x2}{1:x2}{2:x2}", _r, _g, _b);
+        }
+    }
+}
diff --git a/Software/Visual_Studio/Tango.AnimatedGif/Decoding/GifCommentExtension.cs b/Software/Visual_Studio/Tango.AnimatedGif/Decoding/GifCommentExtension.cs
new file mode 100644
index 000000000..cde458d0f
--- /dev/null
+++ b/Software/Visual_Studio/Tango.AnimatedGif/Decoding/GifCommentExtension.cs
@@ -0,0 +1,37 @@
+using System.IO;
+using System.Text;
+
+namespace Tango.AnimatedGif.Decoding
+{
+    internal class GifCommentExtension : GifExtension
+    {
+        internal const int ExtensionLabel = 0xFE;
+
+        public string Text { get; private set; }
+
+        private GifCommentExtension()
+        {
+        }
+
+        internal override GifBlockKind Kind
+        {
+            get { return GifBlockKind.SpecialPurpose; }
+        }
+
+        internal static GifCommentExtension ReadComment(Stream stream)
+        {
+            var comment = new GifCommentExtension();
+            comment.Read(stream);
+            return comment;
+        }
+
+        private void Read(Stream stream)
+        {
+            // Note: at this point, the label (0xFE) has already been read
+
+            var bytes = GifHelpers.ReadDataBlocks(stream, false);
+            if (bytes != null)
+                Text = Encoding.ASCII.GetString(bytes);
+        }
+    }
+}
diff --git a/Software/Visual_Studio/Tango.AnimatedGif/Decoding/GifDecoderException.cs b/Software/Visual_Studio/Tango.AnimatedGif/Decoding/GifDecoderException.cs
new file mode 100644
index 000000000..7ff8ef6e0
--- /dev/null
+++ b/Software/Visual_Studio/Tango.AnimatedGif/Decoding/GifDecoderException.cs
@@ -0,0 +1,16 @@
+using System;
+
+namespace Tango.AnimatedGif.Decoding
+{
+    [Serializable]
+    internal class GifDecoderException : Exception
+    {
+        internal GifDecoderException() { }
+        internal GifDecoderException(string message) : base(message) { }
+        internal GifDecoderException(string message, Exception inner) : base(message, inner) { }
+        protected GifDecoderException(
+          System.Runtime.Serialization.SerializationInfo info,
+          System.Runtime.Serialization.StreamingContext context)
+            : base(info, context) { }
+    }
+}
diff --git a/Software/Visual_Studio/Tango.AnimatedGif/Decoding/GifExtension.cs b/Software/Visual_Studio/Tango.AnimatedGif/Decoding/GifExtension.cs
new file mode 100644
index 000000000..fda8909ec
--- /dev/null
+++ b/Software/Visual_Studio/Tango.AnimatedGif/Decoding/GifExtension.cs
@@ -0,0 +1,32 @@
+using System.Collections.Generic;
+using System.IO;
+
+namespace Tango.AnimatedGif.Decoding
+{
+    internal abstract class GifExtension : GifBlock
+    {
+        internal const int ExtensionIntroducer = 0x21;
+
+        internal static GifExtension ReadExtension(Stream stream, IEnumerable<GifExtension> controlExtensions, bool metadataOnly)
+        {
+            // Note: at this point, the Extension Introducer (0x21) has already been read
+
+            int label = stream.ReadByte();
+            if (label < 0)
+                throw GifHelpers.UnexpectedEndOfStreamException();
+            switch (label)
+            {
+                case GifGraphicControlExtension.ExtensionLabel:
+                    return GifGraphicControlExtension.ReadGraphicsControl(stream);
+                case GifCommentExtension.ExtensionLabel:
+                    return GifCommentExtension.ReadComment(stream);
+                case GifPlainTextExtension.ExtensionLabel:
+                    return GifPlainTextExtension.ReadPlainText(stream, controlExtensions, metadataOnly);
+                case GifApplicationExtension.ExtensionLabel:
+                    return GifApplicationExtension.ReadApplication(stream);
+                default:
+                    throw GifHelpers.UnknownExtensionTypeException(label);
+            }
+        }
+    }
+}
diff --git a/Software/Visual_Studio/Tango.AnimatedGif/Decoding/GifFile.cs b/Software/Visual_Studio/Tango.AnimatedGif/Decoding/GifFile.cs
new file mode 100644
index 000000000..500ce12a8
--- /dev/null
+++ b/Software/Visual_Studio/Tango.AnimatedGif/Decoding/GifFile.cs
@@ -0,0 +1,86 @@
+using System.Collections.Generic;
+using System.IO;
+using System.Linq;
+
+namespace Tango.AnimatedGif.Decoding
+{
+    internal class GifFile
+    {
+        public GifHeader Header { get; private set; }
+        public GifColor[] GlobalColorTable { get; set; }
+        public IList<GifFrame> Frames { get; set; }
+        public IList<GifExtension> Extensions { get; set; }
+        public ushort RepeatCount { get; set; }
+
+        private GifFile()
+        {
+        }
+
+        internal static GifFile ReadGifFile(Stream stream, bool metadataOnly)
+        {
+            var file = new GifFile();
+            file.Read(stream, metadataOnly);
+            return file;
+        }
+
+        private void Read(Stream stream, bool metadataOnly)
+        {
+            Header = GifHeader.ReadHeader(stream);
+
+            if (Header.LogicalScreenDescriptor.HasGlobalColorTable)
+            {
+                GlobalColorTable = GifHelpers.ReadColorTable(stream, Header.LogicalScreenDescriptor.GlobalColorTableSize);
+            }
+            ReadFrames(stream, metadataOnly);
+
+            var netscapeExtension =
+                            Extensions
+                                .OfType<GifApplicationExtension>()
+                                .FirstOrDefault(GifHelpers.IsNetscapeExtension);
+
+            if (netscapeExtension != null)
+                RepeatCount = GifHelpers.GetRepeatCount(netscapeExtension);
+            else
+                RepeatCount = 1;
+        }
+
+        private void ReadFrames(Stream stream, bool metadataOnly)
+        {
+            List<GifFrame> frames = new List<GifFrame>();
+            List<GifExtension> controlExtensions = new List<GifExtension>();
+            List<GifExtension> specialExtensions = new List<GifExtension>();
+            while (true)
+            {
+                var block = GifBlock.ReadBlock(stream, controlExtensions, metadataOnly);
+
+                if (block.Kind == GifBlockKind.GraphicRendering)
+                    controlExtensions = new List<GifExtension>();
+
+                if (block is GifFrame)
+                {
+                    frames.Add((GifFrame)block);
+                }
+                else if (block is GifExtension)
+                {
+                    var extension = (GifExtension)block;
+                    switch (extension.Kind)
+                    {
+                        case GifBlockKind.Control:
+                            controlExtensions.Add(extension);
+                            break;
+                        case GifBlockKind.SpecialPurpose:
+                            specialExtensions.Add(extension);
+                            break;
+                    }
+                }
+                else if (block is GifTrailer)
+                {
+                    break;
+                }
+            }
+
+            this.Frames = frames.AsReadOnly();
+            this.Extensions = specialExtensions.AsReadOnly();
+        }
+    }
+}
diff --git a/Software/Visual_Studio/Tango.AnimatedGif/Decoding/GifFrame.cs b/Software/Visual_Studio/Tango.AnimatedGif/Decoding/GifFrame.cs
new file mode 100644
index 000000000..85740ec87
--- /dev/null
+++ b/Software/Visual_Studio/Tango.AnimatedGif/Decoding/GifFrame.cs
@@ -0,0 +1,47 @@
+using System.Collections.Generic;
+using System.IO;
+using System.Linq;
+
+namespace Tango.AnimatedGif.Decoding
+{
+    internal class GifFrame : GifBlock
+    {
+        internal const int ImageSeparator = 0x2C;
+
+        public GifImageDescriptor Descriptor { get; private set; }
+        public GifColor[] LocalColorTable { get; private set; }
+        public IList<GifExtension> Extensions { get; private set; }
+        public GifImageData ImageData { get; private set; }
+
+        private GifFrame()
+        {
+        }
+
+        internal override GifBlockKind Kind
+        {
+            get { return GifBlockKind.GraphicRendering; }
+        }
+
+        internal static GifFrame ReadFrame(Stream stream, IEnumerable<GifExtension> controlExtensions, bool metadataOnly)
+        {
+            var frame = new GifFrame();
+
+            frame.Read(stream, controlExtensions, metadataOnly);
+
+            return frame;
+        }
+
+        private void Read(Stream stream, IEnumerable<GifExtension> controlExtensions, bool metadataOnly)
+        {
+            // Note: at this point, the Image Separator (0x2C) has already been read
+
+            Descriptor = GifImageDescriptor.ReadImageDescriptor(stream);
+            if (Descriptor.HasLocalColorTable)
+            {
+                LocalColorTable = GifHelpers.ReadColorTable(stream, Descriptor.LocalColorTableSize);
+            }
+            ImageData = GifImageData.ReadImageData(stream, metadataOnly);
+            Extensions = controlExtensions.ToList().AsReadOnly();
+        }
+    }
+}
diff --git a/Software/Visual_Studio/Tango.AnimatedGif/Decoding/GifGraphicControlExtension.cs b/Software/Visual_Studio/Tango.AnimatedGif/Decoding/GifGraphicControlExtension.cs
new file mode 100644
index 000000000..a3782c011
--- /dev/null
+++ b/Software/Visual_Studio/Tango.AnimatedGif/Decoding/GifGraphicControlExtension.cs
@@ -0,0 +1,52 @@
+using System;
+using System.IO;
+
+namespace Tango.AnimatedGif.Decoding
+{
+    // label 0xF9
+    internal class GifGraphicControlExtension : GifExtension
+    {
+        internal const int ExtensionLabel = 0xF9;
+
+        public int BlockSize { get; private set; }
+        public int DisposalMethod { get; private set; }
+        public bool UserInput { get; private set; }
+        public bool HasTransparency { get; private set; }
+        public int Delay { get; private set; }
+        public int TransparencyIndex { get; private set; }
+
+        private GifGraphicControlExtension()
+        {
+
+        }
+
+        internal override GifBlockKind Kind
+        {
+            get { return GifBlockKind.Control; }
+        }
+
+        internal static GifGraphicControlExtension ReadGraphicsControl(Stream stream)
+        {
+            var ext = new GifGraphicControlExtension();
+            ext.Read(stream);
+            return ext;
+        }
+
+        private void Read(Stream stream)
+        {
+            // Note: at this point, the label (0xF9) has already been read
+
+            byte[] bytes = new byte[6];
+            stream.ReadAll(bytes, 0, bytes.Length);
+            BlockSize = bytes[0]; // should always be 4
+            if (BlockSize != 4)
+                throw GifHelpers.InvalidBlockSizeException("Graphic Control Extension", 4, BlockSize);
+            byte packedFields = bytes[1];
+            DisposalMethod = (packedFields & 0x1C) >> 2;
+            UserInput = (packedFields & 0x02) != 0;
+            HasTransparency = (packedFields & 0x01) != 0;
+            Delay = BitConverter.ToUInt16(bytes, 2) * 10; // milliseconds
+            TransparencyIndex = bytes[4];
+        }
+    }
+}
diff --git a/Software/Visual_Studio/Tango.AnimatedGif/Decoding/GifHeader.cs b/Software/Visual_Studio/Tango.AnimatedGif/Decoding/GifHeader.cs
new file mode 100644
index 000000000..b903b83c9
--- /dev/null
+++ b/Software/Visual_Studio/Tango.AnimatedGif/Decoding/GifHeader.cs
@@ -0,0 +1,38 @@
+using System.IO;
+
+namespace Tango.AnimatedGif.Decoding
+{
+    internal class GifHeader : GifBlock
+    {
+        public string Signature { get; private set; }
+        public string Version { get; private set; }
+        public GifLogicalScreenDescriptor LogicalScreenDescriptor { get; private set; }
+
+        private GifHeader()
+        {
+        }
+
+        internal override GifBlockKind Kind
+        {
+            get { return GifBlockKind.Other; }
+        }
+
+        internal static GifHeader ReadHeader(Stream stream)
+        {
+            var header = new GifHeader();
+            header.Read(stream);
+            return header;
+        }
+
+        private void Read(Stream stream)
+        {
+            Signature = GifHelpers.ReadString(stream, 3);
+            if (Signature != "GIF")
+                throw GifHelpers.InvalidSignatureException(Signature);
+            Version = GifHelpers.ReadString(stream, 3);
+            if (Version != "87a" && Version != "89a")
+                throw GifHelpers.UnsupportedVersionException(Version);
+            LogicalScreenDescriptor = GifLogicalScreenDescriptor.ReadLogicalScreenDescriptor(stream);
+        }
+    }
+}
diff --git a/Software/Visual_Studio/Tango.AnimatedGif/Decoding/GifHelpers.cs b/Software/Visual_Studio/Tango.AnimatedGif/Decoding/GifHelpers.cs
new file mode 100644
index 000000000..801b3da27
--- /dev/null
+++ b/Software/Visual_Studio/Tango.AnimatedGif/Decoding/GifHelpers.cs
@@ -0,0 +1,110 @@
+using System;
+using System.IO;
+using System.Text;
+
+namespace Tango.AnimatedGif.Decoding
+{
+    internal static class GifHelpers
+    {
+        public static string ReadString(Stream stream, int length)
+        {
+            byte[] bytes = new byte[length];
+            stream.ReadAll(bytes, 0, length);
+            return Encoding.ASCII.GetString(bytes);
+        }
+
+        public static byte[] ReadDataBlocks(Stream stream, bool discard)
+        {
+            MemoryStream ms = discard ? null : new MemoryStream();
+            using (ms)
+            {
+                int len;
+                while ((len = stream.ReadByte()) > 0)
+                {
+                    byte[] bytes = new byte[len];
+                    stream.ReadAll(bytes, 0, len);
+                    if (ms != null)
+                        ms.Write(bytes, 0, len);
+                }
+                if (ms != null)
+                    return ms.ToArray();
+                return null;
+            }
+        }
+
+        public static GifColor[] ReadColorTable(Stream stream, int size)
+        {
+            int length = 3 * size;
+            byte[] bytes = new byte[length];
+            stream.ReadAll(bytes, 0, length);
+            GifColor[] colorTable = new GifColor[size];
+            for (int i = 0; i < size; i++)
+            {
+                byte r = bytes[3 * i];
+                byte g = bytes[3 * i + 1];
+                byte b = bytes[3 * i + 2];
+                colorTable[i] = new GifColor(r, g, b);
+            }
+            return colorTable;
+        }
+
+        public static bool IsNetscapeExtension(GifApplicationExtension ext)
+        {
+            return ext.ApplicationIdentifier == "NETSCAPE"
+                && Encoding.ASCII.GetString(ext.AuthenticationCode) == "2.0";
+        }
+
+        public static ushort GetRepeatCount(GifApplicationExtension ext)
+        {
+            if (ext.Data.Length >= 3)
+            {
+                return BitConverter.ToUInt16(ext.Data, 1);
+            }
+            return 1;
+        }
+
+        public static Exception UnexpectedEndOfStreamException()
+        {
+            return new GifDecoderException("Unexpected end of stream before trailer was encountered");
+        }
+
+        public static Exception UnknownBlockTypeException(int blockId)
+        {
+            return new GifDecoderException("Unknown block type: 0x" + blockId.ToString("x2"));
+        }
+
+        public static Exception UnknownExtensionTypeException(int extensionLabel)
+        {
+            return new GifDecoderException("Unknown extension type: 0x" + extensionLabel.ToString("x2"));
+        }
+
+        public static Exception InvalidBlockSizeException(string blockName, int expectedBlockSize, int actualBlockSize)
+        {
+            return new GifDecoderException(
+                string.Format(
+                    "Invalid block size for {0}. Expected {1}, but was {2}",
+                    blockName,
+                    expectedBlockSize,
+                    actualBlockSize));
+        }
+
+        public static Exception InvalidSignatureException(string signature)
+        {
+            return new GifDecoderException("Invalid file signature: " + signature);
+        }
+
+        public static Exception UnsupportedVersionException(string version)
+        {
+            return new GifDecoderException("Unsupported version: " + version);
+        }
+
+        public static void ReadAll(this Stream stream, byte[] buffer, int offset, int count)
+        {
+            int totalRead = 0;
+            while (totalRead < count)
+            {
+                totalRead += stream.Read(buffer, offset + totalRead, count - totalRead);
+            }
+        }
+    }
+}
diff --git a/Software/Visual_Studio/Tango.AnimatedGif/Decoding/GifImageData.cs b/Software/Visual_Studio/Tango.AnimatedGif/Decoding/GifImageData.cs
new file mode 100644
index 000000000..32ae1359b
--- /dev/null
+++ b/Software/Visual_Studio/Tango.AnimatedGif/Decoding/GifImageData.cs
@@ -0,0 +1,27 @@
+using System.IO;
+
+namespace Tango.AnimatedGif.Decoding
+{
+    internal class GifImageData
+    {
+        public byte LzwMinimumCodeSize { get; set; }
+        public byte[] CompressedData { get; set; }
+
+        private GifImageData()
+        {
+        }
+
+        internal static GifImageData ReadImageData(Stream stream, bool metadataOnly)
+        {
+            var imgData = new GifImageData();
+            imgData.Read(stream, metadataOnly);
+            return imgData;
+        }
+
+        private void Read(Stream stream, bool metadataOnly)
+        {
+            LzwMinimumCodeSize = (byte)stream.ReadByte();
+            CompressedData = GifHelpers.ReadDataBlocks(stream, metadataOnly);
+        }
+    }
+}
diff --git a/Software/Visual_Studio/Tango.AnimatedGif/Decoding/GifImageDescriptor.cs b/Software/Visual_Studio/Tango.AnimatedGif/Decoding/GifImageDescriptor.cs
new file mode 100644
index 000000000..ad344ef4e
--- /dev/null
+++ b/Software/Visual_Studio/Tango.AnimatedGif/Decoding/GifImageDescriptor.cs
@@ -0,0 +1,43 @@
+using System;
+using System.IO;
+
+namespace Tango.AnimatedGif.Decoding
+{
+    internal class GifImageDescriptor
+    {
+        public int Left { get; private set; }
+        public int Top { get; private set; }
+        public int Width { get; private set; }
+        public int Height { get; private set; }
+        public bool HasLocalColorTable { get; private set; }
+        public bool Interlace { get; private set; }
+        public bool IsLocalColorTableSorted { get; private set; }
+        public int LocalColorTableSize { get; private set; }
+
+        private GifImageDescriptor()
+        {
+        }
+
+        internal static GifImageDescriptor ReadImageDescriptor(Stream stream)
+        {
+            var descriptor = new GifImageDescriptor();
+            descriptor.Read(stream);
+            return descriptor;
+        }
+
+        private void Read(Stream stream)
+        {
+            byte[] bytes = new byte[9];
+            stream.ReadAll(bytes, 0, bytes.Length);
+            Left = BitConverter.ToUInt16(bytes, 0);
+            Top = BitConverter.ToUInt16(bytes, 2);
+            Width = BitConverter.ToUInt16(bytes, 4);
+            Height = BitConverter.ToUInt16(bytes, 6);
+            byte packedFields = bytes[8];
+            HasLocalColorTable = (packedFields & 0x80) != 0;
+            Interlace = (packedFields & 0x40) != 0;
+            IsLocalColorTableSorted = (packedFields & 0x20) != 0;
+            LocalColorTableSize = 1 << ((packedFields & 0x07) + 1);
+        }
+    }
+}
diff --git a/Software/Visual_Studio/Tango.AnimatedGif/Decoding/GifLogicalScreenDescriptor.cs b/Software/Visual_Studio/Tango.AnimatedGif/Decoding/GifLogicalScreenDescriptor.cs
new file mode 100644
index 000000000..55bcb860b
--- /dev/null
+++ b/Software/Visual_Studio/Tango.AnimatedGif/Decoding/GifLogicalScreenDescriptor.cs
@@ -0,0 +1,43 @@
+using System;
+using System.IO;
+
+namespace Tango.AnimatedGif.Decoding
+{
+    internal class GifLogicalScreenDescriptor
+    {
+        public int Width { get; private set; }
+        public int Height { get; private set; }
+        public bool HasGlobalColorTable { get; private set; }
+        public int ColorResolution { get; private set; }
+        public bool IsGlobalColorTableSorted { get; private set; }
+        public int GlobalColorTableSize { get; private set; }
+        public int BackgroundColorIndex { get; private set; }
+        public double PixelAspectRatio { get; private set; }
+
+        internal static GifLogicalScreenDescriptor ReadLogicalScreenDescriptor(Stream stream)
+        {
+            var descriptor = new GifLogicalScreenDescriptor();
+            descriptor.Read(stream);
+            return descriptor;
+        }
+
+        private void Read(Stream stream)
+        {
+            byte[] bytes = new byte[7];
+            stream.ReadAll(bytes, 0, bytes.Length);
+
+            Width = BitConverter.ToUInt16(bytes, 0);
+            Height = BitConverter.ToUInt16(bytes, 2);
+            byte packedFields = bytes[4];
+            HasGlobalColorTable = (packedFields & 0x80) != 0;
+            ColorResolution = ((packedFields & 0x70) >> 4) + 1;
+            IsGlobalColorTableSorted = (packedFields & 0x08) != 0;
+            GlobalColorTableSize = 1 << ((packedFields & 0x07) + 1);
+            BackgroundColorIndex = bytes[5];
+            PixelAspectRatio =
+                bytes[5] == 0
+                    ? 0.0
+                    : (15 + bytes[5]) / 64.0;
+        }
+    }
+}
diff --git a/Software/Visual_Studio/Tango.AnimatedGif/Decoding/GifPlainTextExtension.cs b/Software/Visual_Studio/Tango.AnimatedGif/Decoding/GifPlainTextExtension.cs
new file mode 100644
index 000000000..ddd20c7b7
--- /dev/null
+++ b/Software/Visual_Studio/Tango.AnimatedGif/Decoding/GifPlainTextExtension.cs
@@ -0,0 +1,68 @@
+using System;
+using System.Collections.Generic;
+using System.IO;
+using System.Linq;
+using System.Text;
+
+namespace Tango.AnimatedGif.Decoding
+{
+    // label 0x01
+    internal class GifPlainTextExtension : GifExtension
+    {
+        internal const int ExtensionLabel = 0x01;
+
+        public int BlockSize { get; private set; }
+        public int Left { get; private set; }
+        public int Top { get; private set; }
+        public int Width { get; private set; }
+        public int Height { get; private set; }
+        public int CellWidth { get; private set; }
+        public int CellHeight { get; private set; }
+        public int ForegroundColorIndex { get; private set; }
+        public int BackgroundColorIndex { get; private set; }
+        public string Text { get; private set; }
+
+        public IList<GifExtension> Extensions { get; private set; }
+
+        private GifPlainTextExtension()
+        {
+        }
+
+        internal override GifBlockKind Kind
+        {
+            get { return GifBlockKind.GraphicRendering; }
+        }
+
+        internal static GifPlainTextExtension ReadPlainText(Stream stream, IEnumerable<GifExtension> controlExtensions, bool metadataOnly)
+        {
+            var plainText = new GifPlainTextExtension();
+            plainText.Read(stream, controlExtensions, metadataOnly);
+            return plainText;
+        }
+
+        private void Read(Stream stream, IEnumerable<GifExtension> controlExtensions, bool metadataOnly)
+        {
+            // Note: at this point, the label (0x01) has already been read
+
+            byte[] bytes = new byte[13];
+            stream.ReadAll(bytes,0, bytes.Length);
+
+            BlockSize = bytes[0];
+            if (BlockSize != 12)
+                throw GifHelpers.InvalidBlockSizeException("Plain Text Extension", 12, BlockSize);
+
+            Left = BitConverter.ToUInt16(bytes, 1);
+            Top = BitConverter.ToUInt16(bytes, 3);
+            Width = BitConverter.ToUInt16(bytes, 5);
+            Height = BitConverter.ToUInt16(bytes, 7);
+            CellWidth = bytes[9];
+            CellHeight = bytes[10];
+            ForegroundColorIndex = bytes[11];
+            BackgroundColorIndex = bytes[12];
+
+            var dataBytes = GifHelpers.ReadDataBlocks(stream, metadataOnly);
+            Text = Encoding.ASCII.GetString(dataBytes);
+            Extensions = controlExtensions.ToList().AsReadOnly();
+        }
+    }
+}
diff --git a/Software/Visual_Studio/Tango.AnimatedGif/Decoding/GifTrailer.cs b/Software/Visual_Studio/Tango.AnimatedGif/Decoding/GifTrailer.cs
new file mode 100644
index 000000000..82e153ad3
--- /dev/null
+++ b/Software/Visual_Studio/Tango.AnimatedGif/Decoding/GifTrailer.cs
@@ -0,0 +1,21 @@
+namespace Tango.AnimatedGif.Decoding
+{
+    internal class GifTrailer : GifBlock
+    {
+        internal const int TrailerByte = 0x3B;
+
+        private GifTrailer()
+        {
+        }
+
+        internal override GifBlockKind Kind
+        {
+            get { return GifBlockKind.Other; }
+        }
+
+        internal static GifTrailer ReadTrailer()
+        {
+            return new GifTrailer();
+        }
+    }
+}