Development process
-------------------

Here's the long and short of it:

1. If you are a first-time contributor:

 * Go to `https://github.com/scikit-image/scikit-image
   <http://github.com/scikit-image/scikit-image>`_ and click the
   "fork" button to create your own copy of the project.
 * Clone the project to your local computer:
   ``git clone git@github.com:john_doe/scikit-image.git``
 * Add origin and user branches:
   ``git remote rm origin``
   ``git remote add origin git@github.com:scikit-image/scikit-image.git``
   ``git remote add john_doe git@github.com:john_doe/scikit-image.git``
   Now, ``origin`` refers to the ``scikit-image`` repository and
   ``john_doe`` (your username) to yours.

2. Develop your contribution:

 * Pull the latest changes from upstream
   (``git checkout master ; git pull origin master``)
 * Create a branch for the feature you want to work on.  Since the
   branch name will appear in the merge message, use a sensible name
   such as 'transform-speedups':
   ``git checkout -b transform-speedups``
 * Commit locally as you progress (``git add`` and ``git commit``)

3. To submit your contribution:

 * Push your changes back to GitHub:
   ``git push john_doe transform-speedups``.
 * Go to GitHub.  The new branch will show up with a Pull Request button--click
   it.
 * If you want, post on the `mailing list
   <http://groups.google.com/group/scikit-image>`_ to explain your changes or
   to ask for review.

For a more detailed discussion, read these :doc:`detailed documents
<gitwash/index>` on how to use Git with ``scikit-image``
(`<http://scikit-image.org/docs/dev/gitwash/index.html>`_).

.. note::

   Do *not* ever merge the main branch into yours.  If GitHub indicates that
   the Pull Request can no longer be merged automatically, rebase onto master::

     git fetch origin/master
     git rebase origin/master

   (If you are curious, here's a further discussion on
   the `dangers of rebasing <http://tinyurl.com/lll385>`__.  Also
   see this `LWN article <http://tinyurl.com/nqcbkj>`__.)

* To reviewers: add a short explanation of what a branch did to the merge
  message and, if closing a bug, also add "Closes gh-123" where 123 is the
  bug number.

Guidelines
----------

 * All code should have tests (see `test coverage`_ below for more details).
 * All code should be documented, to the same
   `standard <http://projects.scipy.org/numpy/wiki/CodingStyleGuidelines>`_
   as NumPy and SciPy.
 * For new functionality, always add an example to the
   gallery.
 * No changes should be committed without review.  Ask on the
   `mailing list <http://groups.google.com/group/scikit-image>`_ if
   you get no response to your pull request.
   **Never merge your own pull request.**
 * Examples in the gallery should have a maximum figure width of 8 inches.

Stylistic Guidelines
--------------------

 * Set up your editor to remove trailing whitespace.  Follow `PEP08
   <www.python.org/dev/peps/pep-0008/>`__.  Check code with pyflakes / flake8.

 * Use numpy data types instead of strings (``np.uint8`` instead of
   ``"uint8"``).

 * Use the following import conventions::

     import numpy as np
     import matplotlib.pyplot as plt

     cimport numpy as cnp # in Cython code

 * When documenting array parameters, use ``image : (M, N) ndarray``,
   ``image : (M, N, 3) ndarray`` and then refer to ``M`` and ``N`` in the
   docstring.

 * Functions should support all input image dtypes.  Use utility functions such
   as ``img_as_float`` to help convert to an appropriate type.  The output
   format can be whatever is most efficient.  This allows us to string together
   several functions into a pipeline, e.g.::

     hough(canny(my_image))

 * Use `Py_ssize_t` as data type for all indexing, shape and size variables in
   C/C++ and Cython code.

Test coverage
-------------

Tests for a module should ideally cover all code in that module,
i.e., statement coverage should be at 100%.

To measure the test coverage, install
`coverage.py <http://nedbatchelder.com/code/coverage/>`__
(using ``easy_install coverage``) and then run::

  $ make coverage

This will print a report with one line for each file in `skimage`,
detailing the test coverage::

  Name                                             Stmts   Exec  Cover   Missing
  ------------------------------------------------------------------------------
  skimage/color/colorconv                             77     77   100%
  skimage/filter/__init__                              1      1   100%
  ...

Bugs
----

Please `report bugs on GitHub <https://github.com/scikit-image/scikit-image/issues>`_.