add `set_cand_alphabet`

cnocr/cn_ocr.py

@@ -160,14 +160,12 @@ class CnOcr(object):
         root = os.path.join(root, MODEL_VERSION)
         self._model_dir = os.path.join(root, self._model_name)
         self._assert_and_prepare_model_files()
-        self._alphabet, inv_alph_dict = read_charset(
+        self._alphabet, self._inv_alph_dict = read_charset(
             os.path.join(self._model_dir, 'label_cn.txt')
         )
 
         self._cand_alph_idx = None
-        if cand_alphabet is not None:
-            self._cand_alph_idx = [0] + [inv_alph_dict[word] for word in cand_alphabet]
-            self._cand_alph_idx.sort()
+        self.set_cand_alphabet(cand_alphabet)
 
         self._hp = Hyperparams()
         self._hp._loss_type = None  # infer mode
@@ -214,6 +212,18 @@ class CnOcr(object):
         )
         return mod
 
+    def set_cand_alphabet(self, cand_alphabet):
+        """
+        设置待识别字符的候选集合。
+        :param cand_alphabet: 待识别字符所在的候选集合。默认为 `None`，表示不限定识别字符范围
+        :return: None
+        """
+        if cand_alphabet is None:
+            self._cand_alph_idx = None
+        else:
+            self._cand_alph_idx = [0] + [self._inv_alph_dict[word] for word in cand_alphabet]
+            self._cand_alph_idx.sort()
+
     def ocr(self, img_fp):
         """
         :param img_fp: image file path; or color image mx.nd.NDArray or np.ndarray,

tests/test_cnocr.py

@@ -177,9 +177,7 @@ def test_gray_aug(img_fp, expected):
     print(res_img.shape, res_img.dtype)
 
 
-def test_cand_alphabet():
-    from cnocr import NUMBERS
-
+def test_cand_alphabet1():
     img_fp = os.path.join(example_dir, 'hybrid.png')
 
     ocr = CnOcr(name='instance1')
@@ -195,6 +193,22 @@ def test_cand_alphabet():
     assert len(pred) == 1 and pred[0] == '012345678'
 
 
+def test_cand_alphabet2():
+    img_fp = os.path.join(example_dir, 'hybrid.png')
+
+    ocr = CnOcr(name='instance1')
+    pred = ocr.ocr(img_fp)
+    pred = [''.join(line_p) for line_p in pred]
+    print("Predicted Chars:", pred)
+    assert len(pred) == 1 and pred[0] == 'o12345678'
+
+    ocr.set_cand_alphabet(NUMBERS)
+    pred = ocr.ocr(img_fp)
+    pred = [''.join(line_p) for line_p in pred]
+    print("Predicted Chars:", pred)
+    assert len(pred) == 1 and pred[0] == '012345678'
+
+
 INSTANCE_ID = 0