Add preprocessing common to OCR tasks (#10217)

Add preprocessing to options

paddleocr.py

@@ -43,7 +43,7 @@ from tools.infer import predict_system
 from ppocr.utils.logging import get_logger
 
 logger = get_logger()
-from ppocr.utils.utility import check_and_read, get_image_file_list
+from ppocr.utils.utility import check_and_read, get_image_file_list, alpha_to_color, binarize_img
 from ppocr.utils.network import maybe_download, download_with_progressbar, is_link, confirm_model_dir_url
 from tools.infer.utility import draw_ocr, str2bool, check_gpu
 from ppstructure.utility import init_args, draw_structure_result
@@ -424,7 +424,7 @@ def get_model_config(type, version, model_type, lang):
 
 def img_decode(content: bytes):
     np_arr = np.frombuffer(content, dtype=np.uint8)
-    return cv2.imdecode(np_arr, cv2.IMREAD_COLOR)
+    return cv2.imdecode(np_arr, cv2.IMREAD_UNCHANGED)
 
 
 def check_img(img):
@@ -510,7 +510,7 @@ class PaddleOCR(predict_system.TextSystem):
         super().__init__(params)
         self.page_num = params.page_num
 
-    def ocr(self, img, det=True, rec=True, cls=True):
+    def ocr(self, img, det=True, rec=True, cls=True, bin=False, inv=False, alpha_color=(255, 255, 255)):
         """
         OCR with PaddleOCR
         args：
@@ -518,6 +518,9 @@ class PaddleOCR(predict_system.TextSystem):
             det: use text detection or not. If False, only rec will be exec. Default is True
             rec: use text recognition or not. If False, only det will be exec. Default is True
             cls: use angle classifier or not. Default is True. If True, the text with rotation of 180 degrees can be recognized. If no text is rotated by 180 degrees, use cls=False to get better performance. Text with rotation of 90 or 270 degrees can be recognized even if cls=False.
+            bin: binarize image to black and white. Default is False.
+            inv: invert image colors. Default is False.
+            alpha_color: set RGB color Tuple for transparent parts replacement. Default is pure white.
         """
         assert isinstance(img, (np.ndarray, list, str, bytes))
         if isinstance(img, list) and det == True:
@@ -532,14 +535,24 @@ class PaddleOCR(predict_system.TextSystem):
         # for infer pdf file
         if isinstance(img, list):
             if self.page_num > len(img) or self.page_num == 0:
-                imgs=img
+                imgs = img
             else:
                 imgs = img[:self.page_num]
         else:
             imgs = [img]
+
+        def preprocess_image(_image):
+            _image = alpha_to_color(_image, alpha_color)
+            if inv:
+                _image = cv2.bitwise_not(_image)
+            if bin:
+                _image = binarize_img(_image)
+            return _image
+
         if det and rec:
             ocr_res = []
             for idx, img in enumerate(imgs):
+                img = preprocess_image(img)
                 dt_boxes, rec_res, _ = self.__call__(img, cls)
                 if not dt_boxes and not rec_res:
                     ocr_res.append(None)
@@ -551,6 +564,7 @@ class PaddleOCR(predict_system.TextSystem):
         elif det and not rec:
             ocr_res = []
             for idx, img in enumerate(imgs):
+                img = preprocess_image(img)
                 dt_boxes, elapse = self.text_detector(img)
                 if not dt_boxes:
                     ocr_res.append(None)
@@ -563,6 +577,7 @@ class PaddleOCR(predict_system.TextSystem):
             cls_res = []
             for idx, img in enumerate(imgs):
                 if not isinstance(img, list):
+                    img = preprocess_image(img)
                     img = [img]
                 if self.use_angle_cls and cls:
                     img, cls_res_tmp, elapse = self.text_classifier(img)
@@ -664,10 +679,15 @@ def main():
         img_name = os.path.basename(img_path).split('.')[0]
         logger.info('{}{}{}'.format('*' * 10, img_path, '*' * 10))
         if args.type == 'ocr':
-            result = engine.ocr(img_path,
-                                det=args.det,
-                                rec=args.rec,
-                                cls=args.use_angle_cls)
+            result = engine.ocr(
+                img_path,
+                det=args.det,
+                rec=args.rec,
+                cls=args.use_angle_cls,
+                bin=args.binarize,
+                inv=args.invert,
+                alpha_color=args.alphacolor
+            )
             if result is not None:
                 for idx in range(len(result)):
                     res = result[idx]

ppocr/utils/utility.py

@@ -71,6 +71,25 @@ def get_image_file_list(img_file):
     imgs_lists = sorted(imgs_lists)
     return imgs_lists
 
+def binarize_img(img):
+    if len(img.shape) == 3 and img.shape[2] == 3:
+        gray = cv2.cvtColor(img, cv2.COLOR_BGR2GRAY) # conversion to grayscale image
+        # use cv2 threshold binarization
+        _, gray = cv2.threshold(gray, 0, 255, cv2.THRESH_BINARY + cv2.THRESH_OTSU)
+        img = cv2.cvtColor(gray, cv2.COLOR_GRAY2BGR)
+    return img
+
+def alpha_to_color(img, alpha_color=(255, 255, 255)):
+    if len(img.shape) == 3 and img.shape[2] == 4:
+        B, G, R, A = cv2.split(img)
+        alpha = A / 255
+
+        R = (alpha_color[0] * (1 - alpha) + R * alpha).astype(np.uint8)
+        G = (alpha_color[1] * (1 - alpha) + G * alpha).astype(np.uint8)
+        B = (alpha_color[2] * (1 - alpha) + B * alpha).astype(np.uint8)
+
+        img = cv2.merge((B, G, R))
+    return img
 
 def check_and_read(img_path):
     if os.path.basename(img_path)[-3:].lower() == 'gif':

ppstructure/utility.py

@@ -15,7 +15,7 @@ import random
 import ast
 from PIL import Image, ImageDraw, ImageFont
 import numpy as np
-from tools.infer.utility import draw_ocr_box_txt, str2bool, init_args as infer_args
+from tools.infer.utility import draw_ocr_box_txt, str2bool, str2int_tuple, init_args as infer_args
 
 
 def init_args():
@@ -98,6 +98,21 @@ def init_args():
         type=str2bool,
         default=False,
         help='Whether to use pdf2docx api')
+    parser.add_argument(
+        "--invert",
+        type=str2bool,
+        default=False,
+        help='Whether to invert image before processing')
+    parser.add_argument(
+        "--binarize",
+        type=str2bool,
+        default=False,
+        help='Whether to threshold binarize image before processing')
+    parser.add_argument(
+        "--alphacolor",
+        type=str2int_tuple,
+        default=(255, 255, 255),
+        help='Replacement color for the alpha channel, if the latter is present; R,G,B integers')
 
     return parser
 

tools/infer/utility.py

@@ -28,8 +28,10 @@ from ppocr.utils.logging import get_logger
 
 
 def str2bool(v):
-    return v.lower() in ("true", "t", "1")
+    return v.lower() in ("true", "yes", "t", "y", "1")
 
+def str2int_tuple(v):
+    return tuple([int(i.strip()) for i in v.split(",")])
 
 def init_args():
     parser = argparse.ArgumentParser()