C# - ImageCodecInfo 사용 시 System.Drawing.Image와 System.Drawing.Bitmap에 따른 Save 성능 차이

Bitmap을 이용해 JPG 파일로 저장하는 코드를 좀 더 범용적으로 사용하려고 Image로 바꿨더니 성능이 낮아졌습니다. 이상하군요, 정말 그런지 다음과 같은 코드로 테스트를 할 수 있습니다.

using System.Diagnostics;
using System.Drawing;
using System.Drawing.Imaging;

internal class Program
{
    static void Main(string[] args)
    {
        Image img = Bitmap.FromFile("C:\\temp\\SingAgain_No_48.png");
        Bitmap bmp = new Bitmap(img);

        ImageCodecInfo? jpgEncoder = GetEncoder(ImageFormat.Jpeg);

        System.Drawing.Imaging.Encoder myEncoder = System.Drawing.Imaging.Encoder.Quality;
        EncoderParameters myEncoderParameters = new EncoderParameters(1);
        EncoderParameter myEncoderParameter = new EncoderParameter(myEncoder, 80L);
        myEncoderParameters.Param[0] = myEncoderParameter;

        Action<int, string, Action<object, ImageCodecInfo?, EncoderParameters>, object, ImageCodecInfo?, EncoderParameters> action =
            (loopCount, title, work, arg0, arg1, arg2) =>
        {

            for (int i = 0; i < loopCount; i++)
            {
                Stopwatch st = new Stopwatch();
                st.Start();
                work(arg0, arg1, arg2);
                st.Stop();

                if (loopCount != 1)
                {
                    Console.WriteLine(title + " : " + st.ElapsedMilliseconds);
                }
            }
        };

        action(1, "Bitmap", UseBitmap, bmp, jpgEncoder, myEncoderParameters);
        action(5, "Bitmap", UseBitmap, bmp, jpgEncoder, myEncoderParameters);

        action(1, "Image", UseImage, img, jpgEncoder, myEncoderParameters);
        action(5, "Image", UseImage, img, jpgEncoder, myEncoderParameters);
    }

    static void UseBitmap(object bitmapObj, ImageCodecInfo? encoder, EncoderParameters encoderParameter)
    {
        Bitmap? bitmap = bitmapObj as Bitmap;
        MemoryStream jpgStream = new MemoryStream();
        bitmap?.Save(jpgStream, encoder, encoderParameter);
    }

    static void UseImage(object imgObj, ImageCodecInfo? encoder, EncoderParameters encoderParameter)
    {
        Image? img = imgObj as Image;
        MemoryStream jpgStream = new MemoryStream();
        img?.Save(jpgStream, encoder, encoderParameter);
    }

    private static ImageCodecInfo? GetEncoder(ImageFormat format)
    {
        ImageCodecInfo[] codecs = ImageCodecInfo.GetImageEncoders();
        foreach (ImageCodecInfo codec in codecs)
        {
            if (codec.FormatID == format.Guid)
            {
                return codec;
            }
        }

        return null;
    }
}

// .NET Framework 4.8 + x64 Release + 이미지 1922 x 1082
Bitmap : 12
Bitmap : 12
Bitmap : 12
Bitmap : 12
Bitmap : 12
Image : 36
Image : 35
Image : 34
Image : 34
Image : 34

// .NET 7 + x64 Release + 이미지 1922 x 1082
Bitmap : 10
Bitmap : 11
Bitmap : 10
Bitmap : 10
Bitmap : 10
Image : 44
Image : 43
Image : 42
Image : 42
Image : 42

static void UseImage(object imgObj, ImageCodecInfo? encoder, EncoderParameters encoderParameter)
{
    Image? img = imgObj as Image;
    Bitmap? bitmap = new Bitmap(img);
    MemoryStream jpgStream = new MemoryStream();
    bitmap?.Save(jpgStream, encoder, encoderParameter);
}

// .NET Framework 4.8 + x64 Release + 이미지 1922 x 1082
Bitmap : 22
Bitmap : 23
Bitmap : 22
Bitmap : 23
Bitmap : 23
Image : 35
Image : 35
Image : 34
Image : 34
Image : 35

// .NET 7 + x64 Release + 이미지 1922 x 1082
Bitmap : 20
Bitmap : 20
Bitmap : 19
Bitmap : 19
Bitmap : 19
Image : 42
Image : 42
Image : 42
Image : 44
Image : 42