127 lines
4.2 KiB
ReStructuredText
127 lines
4.2 KiB
ReStructuredText
.. _labeled_faces_in_the_wild_dataset:
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The Labeled Faces in the Wild face recognition dataset
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This dataset is a collection of JPEG pictures of famous people collected
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over the internet, all details are available on the official website:
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http://vis-www.cs.umass.edu/lfw/
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Each picture is centered on a single face. The typical task is called
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Face Verification: given a pair of two pictures, a binary classifier
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must predict whether the two images are from the same person.
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An alternative task, Face Recognition or Face Identification is:
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given the picture of the face of an unknown person, identify the name
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of the person by referring to a gallery of previously seen pictures of
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identified persons.
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Both Face Verification and Face Recognition are tasks that are typically
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performed on the output of a model trained to perform Face Detection. The
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most popular model for Face Detection is called Viola-Jones and is
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implemented in the OpenCV library. The LFW faces were extracted by this
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face detector from various online websites.
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**Data Set Characteristics:**
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================= =======================
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Classes 5749
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Samples total 13233
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Dimensionality 5828
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Features real, between 0 and 255
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================= =======================
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Usage
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~~~~~
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``scikit-learn`` provides two loaders that will automatically download,
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cache, parse the metadata files, decode the jpeg and convert the
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interesting slices into memmapped numpy arrays. This dataset size is more
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than 200 MB. The first load typically takes more than a couple of minutes
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to fully decode the relevant part of the JPEG files into numpy arrays. If
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the dataset has been loaded once, the following times the loading times
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less than 200ms by using a memmapped version memoized on the disk in the
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``~/scikit_learn_data/lfw_home/`` folder using ``joblib``.
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The first loader is used for the Face Identification task: a multi-class
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classification task (hence supervised learning)::
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>>> from sklearn.datasets import fetch_lfw_people
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>>> lfw_people = fetch_lfw_people(min_faces_per_person=70, resize=0.4)
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>>> for name in lfw_people.target_names:
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... print(name)
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...
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Ariel Sharon
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Colin Powell
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Donald Rumsfeld
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George W Bush
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Gerhard Schroeder
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Hugo Chavez
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Tony Blair
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The default slice is a rectangular shape around the face, removing
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most of the background::
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>>> lfw_people.data.dtype
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dtype('float32')
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>>> lfw_people.data.shape
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(1288, 1850)
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>>> lfw_people.images.shape
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(1288, 50, 37)
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Each of the ``1140`` faces is assigned to a single person id in the ``target``
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array::
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>>> lfw_people.target.shape
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(1288,)
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>>> list(lfw_people.target[:10])
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[5, 6, 3, 1, 0, 1, 3, 4, 3, 0]
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The second loader is typically used for the face verification task: each sample
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is a pair of two picture belonging or not to the same person::
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>>> from sklearn.datasets import fetch_lfw_pairs
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>>> lfw_pairs_train = fetch_lfw_pairs(subset='train')
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>>> list(lfw_pairs_train.target_names)
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['Different persons', 'Same person']
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>>> lfw_pairs_train.pairs.shape
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(2200, 2, 62, 47)
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>>> lfw_pairs_train.data.shape
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(2200, 5828)
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>>> lfw_pairs_train.target.shape
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(2200,)
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Both for the :func:`sklearn.datasets.fetch_lfw_people` and
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:func:`sklearn.datasets.fetch_lfw_pairs` function it is
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possible to get an additional dimension with the RGB color channels by
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passing ``color=True``, in that case the shape will be
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``(2200, 2, 62, 47, 3)``.
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The :func:`sklearn.datasets.fetch_lfw_pairs` datasets is subdivided into
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3 subsets: the development ``train`` set, the development ``test`` set and
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an evaluation ``10_folds`` set meant to compute performance metrics using a
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10-folds cross validation scheme.
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.. topic:: References:
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* `Labeled Faces in the Wild: A Database for Studying Face Recognition
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in Unconstrained Environments.
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<http://vis-www.cs.umass.edu/lfw/lfw.pdf>`_
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Gary B. Huang, Manu Ramesh, Tamara Berg, and Erik Learned-Miller.
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University of Massachusetts, Amherst, Technical Report 07-49, October, 2007.
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Examples
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~~~~~~~~
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:ref:`sphx_glr_auto_examples_applications_plot_face_recognition.py`
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