import os.path
import numpy as np
from numpy.testing import *
from numpy.testing.decorators import skipif

from tempfile import NamedTemporaryFile

from skimage import data_dir
from skimage.io import imread, imsave, use_plugin, reset_plugins
import skimage.io as sio

try:
    import imread as _imread
    use_plugin('imread')
except ImportError:
    imread_available = False
else:
    imread_available = True

np.random.seed(0)


def teardown():
    reset_plugins()


@skipif(not imread_available)
def test_imread_flatten():
    # a color image is flattened
    img = imread(os.path.join(data_dir, 'color.png'), flatten=True)
    assert img.ndim == 2
    assert img.dtype == np.float64
    img = imread(os.path.join(data_dir, 'camera.png'), flatten=True)
    # check that flattening does not occur for an image that is grey already.
    assert np.sctype2char(img.dtype) in np.typecodes['AllInteger']


@skipif(not imread_available)
def test_imread_palette():
    img = imread(os.path.join(data_dir, 'palette_color.png'))
    assert img.ndim == 3


@skipif(not imread_available)
def test_imread_truncated_jpg():
    assert_raises((RuntimeError, ValueError),
                  sio.imread,
                  os.path.join(data_dir, 'truncated.jpg'))


@skipif(not imread_available)
def test_bilevel():
    expected = np.zeros((10, 10), bool)
    expected[::2] = 1

    img = imread(os.path.join(data_dir, 'checker_bilevel.png'))
    assert_array_equal(img, expected)


class TestSave:
    def roundtrip(self, x, scaling=1):
        f = NamedTemporaryFile(suffix='.png')
        fname = f.name
        f.close()
        imsave(fname, x)
        y = imread(fname)

        assert_array_almost_equal((x * scaling).astype(np.int32), y)

    @skipif(not imread_available)
    def test_imsave_roundtrip(self):
        dtype = np.uint8
        for shape in [(10, 10), (10, 10, 3), (10, 10, 4)]:
            x = np.ones(shape, dtype=dtype) * np.random.rand(*shape)

            if np.issubdtype(dtype, float):
                yield self.roundtrip, x, 255
            else:
                x = (x * 255).astype(dtype)
                yield self.roundtrip, x

if __name__ == "__main__":
    run_module_suite()