resolves #106: implemented missing method and added tests

functional_tests/FYLM141111001.py

@@ -66,3 +66,15 @@ class FunctionalTests(unittest.TestCase):
     def test_iteration_backwards(self):
         images = [image for image in self.nd2[:10:-1]]
         self.assertEqual(len(images), 10)
+
+    def test_get_image_by_attribute_ok(self):
+        image = self.nd2.get_image(4, 0, "GFP", 1)
+        self.assertIsNotNone(image)
+        image = self.nd2.get_image(4, 0, "", 0)
+        self.assertIsNotNone(image)
+        image = self.nd2.get_image(4, 0, "", 1)
+        self.assertIsNotNone(image)
+
+    def test_get_image_by_attribute_none(self):
+        image = self.nd2.get_image(4, 0, "GFP", 0)
+        self.assertIsNone(image)

nd2reader/driver/v3.py

@@ -101,3 +101,17 @@ class V3Driver(object):
         if np.any(image_data):
             return timestamp, Image(image_data)
         raise NoImageError
+
+    def get_image_by_attributes(self, frame_number, field_of_view, channel_name, z_level, height, width):
+        image_group_number = self._calculate_image_group_number(frame_number, field_of_view, z_level)
+        try:
+            timestamp, raw_image_data = self._get_raw_image_data(image_group_number,
+                                                                 self._channel_offset[channel_name],
+                                                                 height,
+                                                                 width)
+            image = Image(raw_image_data)
+            image.add_params(timestamp, frame_number, field_of_view, channel_name, z_level)
+        except (TypeError, NoImageError):
+            return None
+        else:
+            return image

nd2reader/interface.py

@@ -159,7 +159,7 @@ class Nd2(object):
         :rtype: nd2reader.model.Image()
 
         """
-        return self._driver.get_image_by_attributes(frame_number, field_of_view, channel_name, z_level)
+        return self._driver.get_image_by_attributes(frame_number, field_of_view, channel_name, z_level, self.height, self.width)
 
     def close(self):
         self._fh.close()