项目结构调整

Others/WpfAnimatedGif/Decoding/GifHeader.cs

@@ -0,0 +1,38 @@
+using System.IO;
+
+namespace WpfAnimatedGif.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);
+        }
+    }
+}