finished ocr daemon update

tools/OcrDaemon/ImagePreprocessor.cs

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+namespace OcrDaemon;
+
+using System.Drawing;
+using OpenCvSharp;
+using OpenCvSharp.Extensions;
+
+static class ImagePreprocessor
+{
+    /// <summary>
+    /// Pre-process an image for OCR using morphological white top-hat filtering.
+    /// Isolates bright tooltip text, suppresses dim background text visible through overlay.
+    /// Pipeline: grayscale → morphological top-hat → Otsu binary → 2x upscale
+    /// </summary>
+    public static Bitmap PreprocessForOcr(Bitmap src)
+    {
+        using var mat = BitmapConverter.ToMat(src);
+        using var gray = new Mat();
+        Cv2.CvtColor(mat, gray, ColorConversionCodes.BGRA2GRAY);
+
+        // Morphological white top-hat: isolates bright text on dark background
+        // Kernel size 25x25 captures text strokes, suppresses dim background text
+        using var kernel = Cv2.GetStructuringElement(MorphShapes.Rect, new OpenCvSharp.Size(25, 25));
+        using var tophat = new Mat();
+        Cv2.MorphologyEx(gray, tophat, MorphTypes.TopHat, kernel);
+
+        // Otsu binarization: automatic threshold, black text on white
+        using var binary = new Mat();
+        Cv2.Threshold(tophat, binary, 0, 255, ThresholdTypes.BinaryInv | ThresholdTypes.Otsu);
+
+        // 2x upscale for better LSTM recognition
+        using var upscaled = new Mat();
+        Cv2.Resize(binary, upscaled, new OpenCvSharp.Size(binary.Width * 2, binary.Height * 2),
+            interpolation: InterpolationFlags.Cubic);
+
+        return BitmapConverter.ToBitmap(upscaled);
+    }
+}