Return to ImageSharp

coz the perfomance issue was fixed by Perfare in later commits

AssetStudioGUI/DirectBitmap.cs

@@ -0,0 +1,43 @@
+using System;
+using System.Drawing;
+using System.Drawing.Imaging;
+using System.Runtime.InteropServices;
+
+namespace AssetStudioGUI
+{
+    public sealed class DirectBitmap : IDisposable
+    {
+        public DirectBitmap(byte[] buff, int width, int height)
+        {
+            Width = width;
+            Height = height;
+            Bits = buff;
+            m_handle = GCHandle.Alloc(Bits, GCHandleType.Pinned);
+            m_bitmap = new Bitmap(Width, Height, Stride, PixelFormat.Format32bppArgb, m_handle.AddrOfPinnedObject());
+        }
+
+        private void Dispose(bool disposing)
+        {
+            if (disposing)
+            {
+                m_bitmap.Dispose();
+                m_handle.Free();
+            }
+            m_bitmap = null;
+        }
+
+        public void Dispose()
+        {
+            Dispose(true);
+        }
+
+        public int Height { get; }
+        public int Width { get; }
+        public int Stride => Width * 4;
+        public byte[] Bits { get; }
+        public Bitmap Bitmap => m_bitmap;
+
+        private Bitmap m_bitmap;
+        private readonly GCHandle m_handle;
+    }
+}