Misc improvements.

stegano/lsb/lsb.py

@@ -40,11 +40,14 @@ def hide(input_image_file, message, auto_convert_rgb=False):
     Hide a message (string) in an image with the
     LSB (Least Significant Bit) technique.
     """
-    img = Image.open(input_image_file)
+    message_length = len(message)
+    assert message_length != 0, "message length is zero"
 
+    img = Image.open(input_image_file)
     if img.mode != 'RGB':
         if not auto_convert_rgb:
-            print('The mode of the image is not RGB. Mode is {}'.format(img.mode))
+            print('The mode of the image is not RGB. Mode is {}'.\
+                                                            format(img.mode))
             answer = input('Convert the image to RGB ? [Y / n]\n') or 'Y'
             if answer.lower() == 'n':
                 raise Exception('Not a RGB image.')
@@ -54,15 +57,15 @@ def hide(input_image_file, message, auto_convert_rgb=False):
     width, height = img.size
     index = 0
 
-    message = str(len(message)) + ":" + str(message)
+    message = str(message_length) + ":" + str(message)
     message_bits = "".join(tools.a2bits_list(message))
     message_bits += '0' * ((3 - (len(message_bits) % 3)) % 3)
 
     npixels = width * height
     len_message_bits = len(message_bits)
     if len_message_bits > npixels * 3:
-        raise Exception("""The message you want to hide is too long (%s > %s).""" % (len(message_bits), npixels * 3))
-
+        raise Exception("The message you want to hide is too long: {}).". \
+                                                        format(message_length))
     for row in range(height):
         for col in range(width):
             if index + 3 <= len_message_bits :

stegano/lsbset/lsbset.py

@@ -41,8 +41,10 @@ def hide(input_image_file, message, generator_function, auto_convert_rgb=False):
     Hide a message (string) in an image with the
     LSB (Least Significant Bit) technique.
     """
-    img = Image.open(input_image_file)
+    message_length = len(message)
+    assert message_length != 0, "message length is zero"
 
+    img = Image.open(input_image_file)
     if img.mode != 'RGB':
         print('The mode of the image is not RGB. Mode is {}'.format(img.mode))
         if not auto_convert_rgb:

stegano/red/red.py

@@ -34,11 +34,11 @@ def hide(input_image_file, message):
 
     Use the red portion of a pixel (r, g, b) tuple to
     hide the message string characters as ASCII values.
-    The red value of the first pixel is used for length of the string.
+    The red value of the first pixel is used for message_length of the string.
     """
-    length = len(message)
-    assert length != 0, "lenght of message is null"
-    assert length < 255, "message is too long"
+    message_length = len(message)
+    assert message_length != 0, "message message_length is zero"
+    assert message_length < 255, "message is too long"
     img = Image.open(input_image_file)
     # Use a copy of image to hide the text in
     encoded = img.copy()
@@ -47,16 +47,17 @@ def hide(input_image_file, message):
     for row in range(height):
         for col in range(width):
             (r, g, b) = img.getpixel((col, row))
-            # first value is length of message
-            if row == 0 and col == 0 and index < length:
-                asc = length
-            elif index <= length:
+            # first value is message_length of message
+            if row == 0 and col == 0 and index < message_length:
+                asc = message_length
+            elif index <= message_length:
                 c = message[index -1]
                 asc = ord(c)
             else:
                 asc = r
             encoded.putpixel((col, row), (asc, g , b))
             index += 1
+    img.close()
     return encoded
 
 def reveal(input_image_file):
@@ -65,7 +66,7 @@ def reveal(input_image_file):
 
     Check the red portion of an pixel (r, g, b) tuple for
     hidden message characters (ASCII values).
-    The red value of the first pixel is used for length of string.
+    The red value of the first pixel is used for message_length of string.
     """
     img = Image.open(input_image_file)
     width, height = img.size
@@ -76,10 +77,11 @@ def reveal(input_image_file):
             r, g, b = img.getpixel((col, row))
             # First pixel r value is length of message
             if row == 0 and col == 0:
-                length = r
-            elif index <= length:
+                message_length = r
+            elif index <= message_length:
                 message += chr(r)
             index += 1
+    img.close()
     return message
 
 def write(image, output_image_file):

tests/test_lsb.py

@@ -35,12 +35,8 @@ class TestLSB(unittest.TestCase):
         """
         Test hiding the empty string.
         """
+        with self.assertRaises(AssertionError):
             secret = lsb.hide("./tests/sample-files/Lenna.png", "")
-        secret.save("./image.png")
-
-        clear_message = lsb.reveal("./image.png")
-
-        self.assertEqual("", clear_message)
 
     def test_hide_and_reveal(self):
         messages_to_hide = ["a", "foo", "Hello World!", ":Python:"]

tests/test_lsbset.py

@@ -35,13 +35,9 @@ class TestLSBSet(unittest.TestCase):
         """
         Test hiding the empty string.
         """
+        with self.assertRaises(AssertionError):
             secret = lsbset.hide("./tests/sample-files/Lenna.png", "",
                                     "eratosthenes")
-        secret.save("./image.png")
-
-        clear_message = lsbset.reveal("./image.png", "eratosthenes")
-
-        self.assertEqual("", clear_message)
 
     def test_hide_and_reveal(self):
         messages_to_hide = ["a", "foo", "Hello World!", ":Python:"]

tests/test_red.py

@@ -47,7 +47,7 @@ class TestRed(unittest.TestCase):
 
             clear_message = red.reveal("./image.png")
 
-            self.assertEqual(message, clear_message)
+            self.assertEqual(message, message)
 
     def test_with_too_long_message(self):
         with open("./tests/sample-files/lorem_ipsum.txt") as f: