scikit-image/skimage/_shared/testing.py

"""Testing utilities."""


import os
import re
from tempfile import NamedTemporaryFile

from skimage import (
    data, io, img_as_uint, img_as_float, img_as_int, img_as_ubyte)
from numpy import testing
import numpy as np


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 expresssion 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)
    temp_file.close()
    fname = temp_file.name
    io.imsave(fname, img, plugin=plugin)
    new = io.imread(fname, plugin=plugin)
    try:
        os.remove(fname)
    except Exception:
        pass
    return new


def ubyte_check(plugin, fmt='png'):
    """Check roundtrip behavior for images that can only be saved as uint8

    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)
    r3 = roundtrip(img3, plugin, fmt)
    testing.assert_allclose(r3, img)

    img4 = img_as_int(img)
    r4 = roundtrip(img4, plugin, fmt)
    testing.assert_allclose(r4, img)

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


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

    All major input types should be handled, except bool is treated
    as ubyte and float can treated as uint16 or float.
    """

    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)
    r3 = roundtrip(img3, plugin, fmt)
    if r3.dtype.kind == 'f':
        testing.assert_allclose(img3, r3)
    else:
        testing.assert_allclose(r3, img_as_uint(img))

    img4 = img_as_int(img)
    r4 = roundtrip(img4, plugin, fmt)
    testing.assert_allclose(r4, img4)

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


if __name__ == '__main__':
    ubyte_check('pil')
    full_range_check('pil')
    ubyte_check('pil', 'bmp')
    full_range_check('pil', 'tiff')