添加项目文件。

WpfAnimatedGif/Decoding/GifBlock.cs

@@ -0,0 +1,28 @@
+using System.Collections.Generic;
+using System.IO;
+
+namespace WpfAnimatedGif.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; }
+    }
+}