Isolate subtitles as black over white background (kudos to u/Yun on hexbear.net)

videocr/video.py

@@ -56,6 +56,7 @@ class Video:
         if not self.use_fullframe:
             # only use bottom half of the frame by default
             img = img[self.height // 2:, :]
+            img = cv2.bitwise_not(cv2.bitwise_and(img, img, mask=cv2.inRange(img, (190, 190, 190), (255, 255, 255))))
         config = '--tessdata-dir "{}"'.format(constants.TESSDATA_DIR)
         try:
             return pytesseract.image_to_data(img, lang=self.lang, config=config)