Update app.py

app.py

@@ -4,7 +4,7 @@ import numpy as np
 
 def preprocess(img):
     img_gray = cv2.cvtColor(img, cv2.COLOR_BGR2GRAY)
-    _, img_thresh = cv2.threshold(img_gray, 127, 255, cv2.THRESH_BINARY)
+    img_thresh = cv2.adaptiveThreshold(img_gray, 255, cv2.ADAPTIVE_THRESH_GAUSSIAN_C, cv2.THRESH_BINARY, 11, 2)
     img_dilate = cv2.dilate(img_thresh, np.ones((3, 3)), iterations=2)
     img_erode = cv2.erode(img_dilate, np.ones((3, 3)), iterations=1)
     return img_erode