scikit-image/skimage/_shared/testing.py

"""Testing utilities."""


import os
import re
import threading
import functools
from tempfile import NamedTemporaryFile

from numpy import testing
import numpy as np
from ._warnings import expected_warnings
import warnings

from .. import data, io, img_as_uint, img_as_float, img_as_int, img_as_ubyte


SKIP_RE = re.compile("(\s*>>>.*?)(\s*)#\s*skip\s+if\s+(.*)$")


def _assert_less(a, b, msg=None):
    message = "%r is not lower than %r" % (a, b)
    if msg is not None:
        message += ": " + msg
    assert a < b, message


def _assert_greater(a, b, msg=None):
    message = "%r is not greater than %r" % (a, b)
    if msg is not None:
        message += ": " + msg
    assert a > b, message


try:
    from nose.tools import assert_less
except ImportError:
    assert_less = _assert_less

try:
    from nose.tools import assert_greater
except ImportError:
    assert_greater = _assert_greater


def doctest_skip_parser(func):
    """ Decorator replaces custom skip test markup in doctests

    Say a function has a docstring::

        >>> something # skip if not HAVE_AMODULE
        >>> something + else
        >>> something # skip if HAVE_BMODULE

    This decorator will evaluate the expression after ``skip if``.  If this
    evaluates to True, then the comment is replaced by ``# doctest: +SKIP``.  If
    False, then the comment is just removed. The expression is evaluated in the
    ``globals`` scope of `func`.

    For example, if the module global ``HAVE_AMODULE`` is False, and module
    global ``HAVE_BMODULE`` is False, the returned function will have docstring::

        >>> something # doctest: +SKIP
        >>> something + else
        >>> something

    """
    lines = func.__doc__.split('\n')
    new_lines = []
    for line in lines:
        match = SKIP_RE.match(line)
        if match is None:
            new_lines.append(line)
            continue
        code, space, expr = match.groups()

        try:
            # Works as a function decorator
            if eval(expr, func.__globals__):
                code = code + space + "# doctest: +SKIP"
        except AttributeError:
            # Works as a class decorator
            if eval(expr, func.__init__.__globals__):
                code = code + space + "# doctest: +SKIP"

        new_lines.append(code)
    func.__doc__ = "\n".join(new_lines)
    return func


def roundtrip(img, plugin, suffix):
    """Save and read an image using a specified plugin"""
    if not '.' in suffix:
        suffix = '.' + suffix
    temp_file = NamedTemporaryFile(suffix=suffix, delete=False)
    fname = temp_file.name
    temp_file.close()
    io.imsave(fname, img, plugin=plugin)
    new = io.imread(fname, plugin=plugin)
    try:
        os.remove(fname)
    except Exception:
        pass
    return new


def color_check(plugin, fmt='png'):
    """Check roundtrip behavior for color images.

    All major input types should be handled as ubytes and read
    back correctly.
    """
    img = img_as_ubyte(data.chelsea())
    r1 = roundtrip(img, plugin, fmt)
    testing.assert_allclose(img, r1)

    img2 = img > 128
    r2 = roundtrip(img2, plugin, fmt)
    testing.assert_allclose(img2.astype(np.uint8), r2)

    img3 = img_as_float(img)
    with expected_warnings(['precision loss']):
        r3 = roundtrip(img3, plugin, fmt)
    testing.assert_allclose(r3, img)

    with expected_warnings(['precision loss']):
        img4 = img_as_int(img)
    if fmt.lower() in (('tif', 'tiff')):
        img4 -= 100
        with expected_warnings(['sign loss']):
            r4 = roundtrip(img4, plugin, fmt)
        testing.assert_allclose(r4, img4)
    else:
        with expected_warnings(['sign loss|precision loss']):
            r4 = roundtrip(img4, plugin, fmt)
            testing.assert_allclose(r4, img_as_ubyte(img4))

    img5 = img_as_uint(img)
    with expected_warnings(['precision loss']):
        r5 = roundtrip(img5, plugin, fmt)
    testing.assert_allclose(r5, img)


def mono_check(plugin, fmt='png'):
    """Check the roundtrip behavior for images that support most types.

    All major input types should be handled.
    """

    img = img_as_ubyte(data.moon())
    r1 = roundtrip(img, plugin, fmt)
    testing.assert_allclose(img, r1)

    img2 = img > 128
    r2 = roundtrip(img2, plugin, fmt)
    testing.assert_allclose(img2.astype(np.uint8), r2)

    img3 = img_as_float(img)
    with expected_warnings(['precision|\A\Z']):
        r3 = roundtrip(img3, plugin, fmt)
    if r3.dtype.kind == 'f':
        testing.assert_allclose(img3, r3)
    else:
        testing.assert_allclose(r3, img_as_uint(img))

    with expected_warnings(['precision loss']):
        img4 = img_as_int(img)
    if fmt.lower() in (('tif', 'tiff')):
        img4 -= 100
        with expected_warnings(['sign loss|\A\Z']):
            r4 = roundtrip(img4, plugin, fmt)
        testing.assert_allclose(r4, img4)
    else:
        with expected_warnings(['precision loss|sign loss']):
            r4 = roundtrip(img4, plugin, fmt)
            testing.assert_allclose(r4, img_as_uint(img4))

    img5 = img_as_uint(img)
    r5 = roundtrip(img5, plugin, fmt)
    testing.assert_allclose(r5, img5)


def setup_test():
    """Default package level setup routine for skimage tests.

    Import packages known to raise warnings, and then
    force warnings to raise errors.

    Also set the random seed to zero.
    """
    warnings.simplefilter('default')

    from scipy import signal, ndimage, special, optimize, linalg
    from scipy.io import loadmat
    from skimage import viewer, filter

    np.random.seed(0)

    warnings.simplefilter('error')


def teardown_test():
    """Default package level teardown routine for skimage tests.

    Restore warnings to default behavior
    """
    warnings.simplefilter('default')


def test_parallel(num_threads=2):
    """Decorator to run the same function multiple times in parallel.

    Parameters
    ----------
    num_threads : int, optional
        The number of times the function is run in parallel.

    """

    assert num_threads > 0

    def wrapper(func):
        @functools.wraps(func)
        def inner(*args, **kwargs):
            threads = []
            for i in range(num_threads - 1):
                thread = threading.Thread(target=func, args=args, kwargs=kwargs)
                threads.append(thread)
            for thread in threads:
                thread.start()

            result = func(*args, **kwargs)

            for thread in threads:
                thread.join()

            return result

        return inner

    return wrapper


if __name__ == '__main__':
    color_check('pil')
    mono_check('pil')
    mono_check('pil', 'bmp')
    mono_check('pil', 'tiff')