Add project files.

AssetStudioUtility/ImageExtensions.cs

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+using SixLabors.ImageSharp;
+using SixLabors.ImageSharp.Formats.Bmp;
+using SixLabors.ImageSharp.Formats.Tga;
+using SixLabors.ImageSharp.PixelFormats;
+using System.IO;
+using System.Runtime.InteropServices;
+
+namespace AssetStudio
+{
+    public static class ImageExtensions
+    {
+        public static void WriteToStream(this Image image, Stream stream, ImageFormat imageFormat)
+        {
+            switch (imageFormat)
+            {
+                case ImageFormat.Jpeg:
+                    image.SaveAsJpeg(stream);
+                    break;
+                case ImageFormat.Png:
+                    image.SaveAsPng(stream);
+                    break;
+                case ImageFormat.Bmp:
+                    image.Save(stream, new BmpEncoder
+                    {
+                        BitsPerPixel = BmpBitsPerPixel.Pixel32,
+                        SupportTransparency = true
+                    });
+                    break;
+                case ImageFormat.Tga:
+                    image.Save(stream, new TgaEncoder
+                    {
+                        BitsPerPixel = TgaBitsPerPixel.Pixel32,
+                        Compression = TgaCompression.None
+                    });
+                    break;
+            }
+        }
+
+        public static MemoryStream ConvertToStream(this Image image, ImageFormat imageFormat)
+        {
+            var stream = new MemoryStream();
+            image.WriteToStream(stream, imageFormat);
+            return stream;
+        }
+
+        public static byte[] ConvertToBytes<TPixel>(this Image<TPixel> image) where TPixel : unmanaged, IPixel<TPixel>
+        {
+            if (image.TryGetSinglePixelSpan(out var pixelSpan))
+            {
+                return MemoryMarshal.AsBytes(pixelSpan).ToArray();
+            }
+            return null;
+        }
+    }
+}