Add WebpReader

StabilityMatrix.Core/Helper/Webp/WebpReader.cs

@@ -0,0 +1,57 @@
+using System.Text;
+
+namespace StabilityMatrix.Core.Helper.Webp;
+
+public class WebpReader(Stream stream) : BinaryReader(stream, Encoding.ASCII, true)
+{
+    private uint headerFileSize;
+
+    public bool GetIsAnimatedFlag()
+    {
+        ReadHeader();
+
+        while (BaseStream.Position < headerFileSize)
+        {
+            if (ReadVoidChunk() is "ANMF" or "ANIM")
+            {
+                return true;
+            }
+        }
+
+        return false;
+    }
+
+    private void ReadHeader()
+    {
+        // RIFF
+        var riff = ReadBytes(4);
+        if (!riff.SequenceEqual([.."RIFF"u8]))
+        {
+            throw new InvalidDataException("Invalid RIFF header");
+        }
+
+        // Size: uint32
+        headerFileSize = ReadUInt32();
+
+        // WEBP
+        var webp = ReadBytes(4);
+        if (!webp.SequenceEqual([.."WEBP"u8]))
+        {
+            throw new InvalidDataException("Invalid WEBP header");
+        }
+    }
+
+    // Read a single chunk and discard its contents
+    private string ReadVoidChunk()
+    {
+        // FourCC: 4 bytes in ASCII
+        var result = ReadBytes(4);
+
+        // Size: uint32
+        var size = ReadUInt32();
+
+        BaseStream.Seek(size, SeekOrigin.Current);
+
+        return Encoding.ASCII.GetString(result);
+    }
+}