switched to new way

src/Poe2Trade.Screen/ImageUtils.cs

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+namespace Poe2Trade.Screen;
+
+using System.Drawing;
+using System.Drawing.Imaging;
+using System.Runtime.InteropServices;
+using SdImageFormat = System.Drawing.Imaging.ImageFormat;
+
+static class ImageUtils
+{
+    public static (byte[] gray, byte[] argb, int stride) BitmapToGrayAndArgb(Bitmap bmp)
+    {
+        int w = bmp.Width, h = bmp.Height;
+        var data = bmp.LockBits(new Rectangle(0, 0, w, h), ImageLockMode.ReadOnly, PixelFormat.Format32bppArgb);
+        byte[] argb = new byte[data.Stride * h];
+        Marshal.Copy(data.Scan0, argb, 0, argb.Length);
+        bmp.UnlockBits(data);
+        int stride = data.Stride;
+
+        byte[] gray = new byte[w * h];
+        for (int y = 0; y < h; y++)
+            for (int x = 0; x < w; x++)
+            {
+                int i = y * stride + x * 4;
+                gray[y * w + x] = (byte)((argb[i] + argb[i + 1] + argb[i + 2]) / 3);
+            }
+        return (gray, argb, stride);
+    }
+
+    public static SdImageFormat GetImageFormat(string path)
+    {
+        var ext = Path.GetExtension(path).ToLowerInvariant();
+        return ext switch
+        {
+            ".jpg" or ".jpeg" => SdImageFormat.Jpeg,
+            ".bmp" => SdImageFormat.Bmp,
+            _ => SdImageFormat.Png,
+        };
+    }
+}