fix: decoding of binary data with null bytes

pylibdmtx/pylibdmtx.py

@@ -178,7 +178,7 @@ def _decode_region(decoder, region, corrections, shrink, return_vertices=False):
 
             if return_vertices:
                 return Decoded(
-                    string_at(msg.contents.output),
+                    string_at(msg.contents.output, msg.contents.outputIdx),
                     Rect_vertices((x00,y00), (x01,y01), (x10,y10), (x11,y11))
                 )
             else:
@@ -188,7 +188,7 @@ def _decode_region(decoder, region, corrections, shrink, return_vertices=False):
                 max_y = max(y00, y11, y10, y01)
 
                 return Decoded(
-                    string_at(msg.contents.output),
+                    string_at(msg.contents.output, msg.contents.outputIdx),
                     Rect(min_x, min_y, max_x - min_x, max_y - min_y)
                     )
 

pylibdmtx/tests/test_pylibdmtx.py

@@ -215,6 +215,47 @@ def test_image_not_large_enough(self):
             encode, b' '*50, size='10x10'
         )
 
+    def test_base256_binary_data_with_null_bytes(self):
+        """Test Base256 scheme encoding and decoding of binary data containing null bytes."""
+        # Create binary data that contains null bytes (0x00)
+        # This represents typical binary data that may contain null bytes
+        binary_data = b'\x01\x02\x00\x03\x04\x00\x05\x06'
+
+        # Encode the binary data using Base256 scheme
+        encoded = encode(binary_data, scheme='Base256')
+
+        # Create PIL image from encoded data
+        image = Image.frombytes('RGB', (encoded.width, encoded.height), encoded.pixels)
+
+        # Decode the image back to binary data
+        decoded_results = decode(image)
+
+        # Verify that binary data with null bytes is preserved correctly
+        self.assertEqual(1, len(decoded_results))
+        decoded_data = decoded_results[0].data
+
+        # The decoded data should exactly match the original binary data
+        self.assertEqual(binary_data, decoded_data, 
+                        "Binary data with null bytes should be preserved during encoding/decoding")
+
+    def test_ascii_scheme_with_null_bytes(self):
+        """Test ASCII scheme encoding and decoding of data containing null bytes."""
+        # Test data with null bytes
+        test_data = b'hello\x00world'
+
+        # Encode using ASCII scheme
+        encoded = encode(test_data, scheme='Ascii')
+        image = Image.frombytes('RGB', (encoded.width, encoded.height), encoded.pixels)
+
+        # Decode and verify the null byte is preserved
+        decoded_results = decode(image)
+        self.assertEqual(1, len(decoded_results))
+        decoded_data = decoded_results[0].data
+
+        # The decoded data should preserve null bytes
+        self.assertEqual(test_data, decoded_data, 
+                        "ASCII scheme should preserve null bytes during encoding/decoding")
+
 
 if __name__ == '__main__':
     unittest.main()