[advanced][databases][mnist] Add V2 version of mnist database

This new version also fixes a bug making in not working
on the platform.

advanced/databases/mnist/5.json

+{
+    "description": "The MNIST Database of Handwritten Digits",
+    "root_folder": "/idiap/group/biometric/databases/mnist",
+    "protocols": [
+        {
+            "name": "idiap",
+            "template": "simple_digit_recognition/1",
+            "views": {
+                "train": {
+                    "view": "View",
+                    "parameters": {
+                        "group": "train"
+                    }
+                },
+                "test": {
+                    "view": "View",
+                    "parameters": {
+                        "group": "test"
+                    }
+                }
+            }
+        }
+    ],
+    "schema_version": 2
+}
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advanced/databases/mnist/5.py

+###############################################################################
+#                                                                             #
+# Copyright (c) 2018 Idiap Research Institute, http://www.idiap.ch/           #
+# Contact: beat.support@idiap.ch                                              #
+#                                                                             #
+# This file is part of the beat.examples module of the BEAT platform.         #
+#                                                                             #
+# Commercial License Usage                                                    #
+# Licensees holding valid commercial BEAT licenses may use this file in       #
+# accordance with the terms contained in a written agreement between you      #
+# and Idiap. For further information contact tto@idiap.ch                     #
+#                                                                             #
+# Alternatively, this file may be used under the terms of the GNU Affero      #
+# Public License version 3 as published by the Free Software and appearing    #
+# in the file LICENSE.AGPL included in the packaging of this file.            #
+# The BEAT platform is distributed in the hope that it will be useful, but    #
+# WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY  #
+# or FITNESS FOR A PARTICULAR PURPOSE.                                        #
+#                                                                             #
+# You should have received a copy of the GNU Affero Public License along      #
+# with the BEAT platform. If not, see http://www.gnu.org/licenses/.           #
+#                                                                             #
+###############################################################################
+
+import numpy as np
+from collections import namedtuple
+
+from beat.backend.python.database import View as BaseView
+
+import bob.db.mnist
+
+
+#----------------------------------------------------------
+
+
+class View(BaseView):
+    """Outputs:
+        - image: "{{ system_user.username }}/array_2d_uint8/1"
+        - id: "{{ system_user.username }}/uint64/1"
+        - class_id: "{{ system_user.username }}/uint64/1"
+
+    One "id" is associated with a given "image".
+    Several "image" are associated with a given "class_id".
+
+    --------------- --------------- --------------- --------------- --------------- ---------------
+    |    image    | |    image    | |    image    | |    image    | |    image    | |    image    |
+    --------------- --------------- --------------- --------------- --------------- ---------------
+    --------------- --------------- --------------- --------------- --------------- ---------------
+    |     id      | |     id      | |     id      | |     id      | |     id      | |     id      |
+    --------------- --------------- --------------- --------------- --------------- ---------------
+    ----------------------------------------------- -----------------------------------------------
+    |                   class_id                  | |                   class_id                  |
+    ----------------------------------------------- -----------------------------------------------
+    """
+
+    def index(self, root_folder, parameters):
+        Entry = namedtuple('Entry', ['class_id', 'id', 'image'])
+
+        # Open the database and load the objects to provide via the outputs
+        db = bob.db.mnist.Database()
+
+        features, labels = db.data(groups=parameters['group'])
+
+        objs = sorted([ (labels[i], i, features[i]) for i in range(len(features)) ],
+                      key=lambda x: (x[0], x[1]))
+
+        return [ Entry(x[0], x[1], x[2]) for x in objs ]
+
+
+    def get(self, output, index):
+        obj = self.objs[index]
+
+        if output == 'class_id':
+            return {
+                'value': np.uint64(obj.class_id)
+            }
+
+        elif output == 'id':
+            return {
+                'value': np.uint64(obj.id)
+            }
+
+        elif output == 'image':
+            return {
+                'value': obj.image.reshape((28, 28))
+            }
+
+
+#----------------------------------------------------------
+
+
+def setup_tests():
+    pass
+
+
+#----------------------------------------------------------
+
+
+# Test the behavior of the views (on fake data)
+if __name__ == '__main__':
+
+    setup_tests()
+
+    # Note: This database can't be tested without the actual data, since
+    # the actual files are needed by this implementation
+
+    view = View()
+    view.objs = view.index(root_folder='', parameters=dict(group='train'))
+    view.get('class_id', 0)
+    view.get('id', 0)
+    view.get('image', 0)

advanced/databases/mnist/5.rst

+The MNIST Database of Handwritten Digits
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