screen: update tresholds on text

screen.go

@@ -67,7 +67,6 @@ 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")
@@ -90,16 +89,37 @@ func (d *Device) GetScreenText(xStart int, xEnd int, yStart int, yEnd int, white
 		}
 	}
 
-	// Convert to grayscale and apply threshold
-	threshold := uint8(160)
+	// Convert to grayscale and compute average brightness
+	gray := image.NewGray(rect)
+	var totalBrightness int
+	for y := 0; y < rect.Dy(); y++ {
+		for x := 0; x < rect.Dx(); x++ {
+			grayVal := color.GrayModel.Convert(cropped.At(x, y)).(color.Gray)
+			gray.Set(x, y, grayVal)
+			totalBrightness += int(grayVal.Y)
+		}
+	}
+	avgBrightness := totalBrightness / (rect.Dx() * rect.Dy())
+
+	// Binarize based on brightness polarity
 	binarized := 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 {
+			grayVal := gray.GrayAt(x, y).Y
+			if avgBrightness < 128 {
+				// Dark background, light text
+				if int(grayVal) > avgBrightness+10 {
 					binarized.SetGray(x, y, color.Gray{Y: 0})
+				} else {
+					binarized.SetGray(x, y, color.Gray{Y: 255})
+				}
+			} else {
+				// Light background, dark text
+				if int(grayVal) < avgBrightness-10 {
+					binarized.SetGray(x, y, color.Gray{Y: 0})
+				} else {
+					binarized.SetGray(x, y, color.Gray{Y: 255})
+				}
 			}
 		}
 	}
@@ -110,7 +130,7 @@ func (d *Device) GetScreenText(xStart int, xEnd int, yStart int, yEnd int, white
 		return "", fmt.Errorf("failed to encode image: %w", err)
 	}
 
-	// Call tesseract
+	// Call Tesseract
 	client := gosseract.NewClient()
 	defer client.Close()
 	client.SetImageFromBytes(buf.Bytes())