Add additional image processing

Ordered process:
1. dilation - thicken white portion of subtitles
2. resize - temporary hardcoded to 47% (assuming subtitles are 68 pixels in height)
3. apply hsv color mask - filter out non gray pixels and filter out pixels that are not bright enough
4. invert image - make it black text on white background
5. add border to top and bottom - assuming subtitles are cropped closely

videocr/video.py

@@ -18,6 +18,8 @@ class Video:
     num_frames: int
     fps: float
     height: int
+    width: int
+    resize_dim: List[int]
     pred_frames: List[PredictedFrame]
     pred_subs: List[PredictedSubtitle]
 
@@ -27,6 +29,9 @@ class Video:
             self.num_frames = int(v.get(cv2.CAP_PROP_FRAME_COUNT))
             self.fps = v.get(cv2.CAP_PROP_FPS)
             self.height = int(v.get(cv2.CAP_PROP_FRAME_HEIGHT))
+            self.width = int(v.get(cv2.CAP_PROP_FRAME_WIDTH))
+            scale_percent = 47 # apparently 32 pixels is the optimal character height for tesseract.
+            self.resize_dim=(int(self.width * scale_percent/100), int(self.height * scale_percent/100))
 
     def run_ocr(self, lang: str, time_start: str, time_end: str,
                 conf_threshold: int, use_fullframe: bool) -> None:
@@ -56,8 +61,16 @@ 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)
+        # dilate and resize
+        img=cv2.resize(cv2.dilate(img, np.ones(2, 2), np.uint8), self.resize_dim, interpolation=cv2.INTER_AREA)
+
+        # mask to filter out non gray-like pixels/pixels that are not bright enough
+        hsv = cv2.cvtColor(img, cv2.COLOR_BGR2HSV)
+        color_mask = cv2.inRange(hsv, (0, 0, 190), (179, 20, 255))
+
+        # apply mask, inverse image so it's black text on white background, add borders to top and bottom
+        img = cv2.copyMakeBorder(cv2.bitwise_not(cv2.bitwise_and(img, img, mask=color_mask)), 10, 10, 0, 0, cv2.BORDER_CONSTANT, None, (255,255,255)
+        config = '--tessdata-dir "{}" --psm 7 -c preserve_interword_spaces=1'.format(constants.TESSDATA_DIR)
         try:
             return pytesseract.image_to_data(img, lang=self.lang, config=config)
         except Exception as e: