overlay and calibration

src/Poe2Trade.Screen/ImagePreprocessor.cs

@@ -6,6 +6,32 @@ using OpenCvSharp.Extensions;
 
 static class ImagePreprocessor
 {
+    /// <summary>
+    /// CLAHE (Contrast Limited Adaptive Histogram Equalization) preprocessing.
+    /// Enhances local contrast — works for both light and dark text on varying backgrounds.
+    /// Pipeline: grayscale -> CLAHE -> upscale (keeps grayscale, lets EasyOCR handle binarization)
+    /// </summary>
+    public static Bitmap PreprocessClahe(Bitmap src, double clipLimit = 3.0, int tileSize = 8, int upscale = 2)
+    {
+        using var mat = BitmapConverter.ToMat(src);
+        using var gray = new Mat();
+        Cv2.CvtColor(mat, gray, ColorConversionCodes.BGRA2GRAY);
+
+        using var clahe = Cv2.CreateCLAHE(clipLimit, new OpenCvSharp.Size(tileSize, tileSize));
+        using var enhanced = new Mat();
+        clahe.Apply(gray, enhanced);
+
+        if (upscale > 1)
+        {
+            using var upscaled = new Mat();
+            Cv2.Resize(enhanced, upscaled, new OpenCvSharp.Size(enhanced.Width * upscale, enhanced.Height * upscale),
+                interpolation: InterpolationFlags.Cubic);
+            return BitmapConverter.ToBitmap(upscaled);
+        }
+
+        return BitmapConverter.ToBitmap(enhanced);
+    }
+
     /// <summary>
     /// Pre-process an image for OCR using morphological white top-hat filtering.
     /// Isolates bright tooltip text, suppresses dim background text visible through overlay.

src/Poe2Trade.Screen/ScreenReader.cs

@@ -54,6 +54,12 @@ public class ScreenReader : IScreenReader
             return Task.FromResult(_pythonBridge.OcrFromBitmap(processed));
         }
 
+        if (preprocess == "clahe")
+        {
+            using var processed = ImagePreprocessor.PreprocessClahe(bitmap);
+            return Task.FromResult(_pythonBridge.OcrFromBitmap(processed));
+        }
+
         return Task.FromResult(_pythonBridge.OcrFromBitmap(bitmap));
     }