adding CaptchaReaderTest

src/captcha/PredictionsDecoder.py

@@ -0,0 +1,24 @@
+import tensorflow as tf
+from tensorflow import keras
+import numpy as np
+
+
+class PredictionsDecoder:
+
+    def __init__(self, captchaLength, num_to_char):
+        self.captchaLength = captchaLength
+        self.num_to_char = num_to_char
+
+    def decode_batch_predictions(self, pred):
+        return self.asStrings(self.ctc_decode(pred))
+
+    def ctc_decode(self, pred):
+        input_len = np.ones(pred.shape[0]) * pred.shape[1]
+        # Use greedy search. For complex tasks, you can use beam search
+        return keras.backend.ctc_decode(pred, input_length=input_len, greedy=True)[0][0][:, :self.captchaLength]
+
+    def asStrings(self, labels):
+        return [self.asString(label) for label in labels]
+
+    def asString(self, label):
+        return tf.strings.reduce_join(self.num_to_char(label)).numpy().decode("utf-8")