项目结构调整

Others/WpfAnimatedGif/Decoding/GifGraphicControlExtension.cs

@@ -0,0 +1,52 @@
+using System;
+using System.IO;
+
+namespace WpfAnimatedGif.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];
+        }
+    }
+}