screen: update tresholds on text

screen.go

@@ -67,21 +67,17 @@ func (d *Device) GetScreenResolution() (int, int, error) {
 	return d.Screenx, d.Screeny, nil
 }
 
-// Get the text on screen in a certain area using gotesseract
 func (d *Device) GetScreenText(xStart int, xEnd int, yStart int, yEnd int, whitelist string, multiline bool) (string, error) {
-	// Take screenshot in memory and get bytes
     data, err := d.RunCommand("exec-out screencap -p")
     if err != nil {
         return "", fmt.Errorf("failed to take screenshot: %w", err)
     }
 
-	// Decode image from bytes
     img, err := png.Decode(bytes.NewReader(data))
     if err != nil {
         return "", fmt.Errorf("failed to decode PNG: %w", err)
     }
 
-	// Crop region
     rect := image.Rect(0, 0, xEnd-xStart, yEnd-yStart)
     cropped := image.NewRGBA(rect)
     for y := yStart; y < yEnd; y++ {
@@ -90,27 +86,45 @@ func (d *Device) GetScreenText(xStart int, xEnd int, yStart int, yEnd int, white
         }
     }
 
-	// Convert to grayscale and apply threshold
-	threshold := uint8(160)
-	binarized := image.NewGray(rect)
+    // Convert to grayscale
+    gray := image.NewGray(rect)
     for y := 0; y < rect.Dy(); y++ {
         for x := 0; x < rect.Dx(); x++ {
-			gray := color.GrayModel.Convert(cropped.At(x, y)).(color.Gray)
-			if gray.Y > threshold {
-				binarized.SetGray(x, y, color.Gray{Y: 255})
-			} else {
+            gray.Set(x, y, color.GrayModel.Convert(cropped.At(x, y)))
+        }
+    }
+
+    // Apply simple mean-based adaptive thresholding
+    binarized := image.NewGray(rect)
+    window := 15 // size of local region
+    for y := 0; y < rect.Dy(); y++ {
+        for x := 0; x < rect.Dx(); x++ {
+            var sum int
+            var count int
+            for dy := -window / 2; dy <= window/2; dy++ {
+                for dx := -window / 2; dx <= window/2; dx++ {
+                    xx := x + dx
+                    yy := y + dy
+                    if xx >= 0 && xx < rect.Dx() && yy >= 0 && yy < rect.Dy() {
+                        sum += int(gray.GrayAt(xx, yy).Y)
+                        count++
+                    }
+                }
+            }
+            mean := sum / count
+            if int(gray.GrayAt(x, y).Y) < mean-10 {
                 binarized.SetGray(x, y, color.Gray{Y: 0})
+            } else {
+                binarized.SetGray(x, y, color.Gray{Y: 255})
             }
         }
     }
 
-	// Encode binarized image to PNG
     var buf bytes.Buffer
     if err := png.Encode(&buf, binarized); err != nil {
         return "", fmt.Errorf("failed to encode image: %w", err)
     }
 
-	// Call tesseract
     client := gosseract.NewClient()
     defer client.Close()
     client.SetImageFromBytes(buf.Bytes())