import imgaug as ia
from imgaug import augmenters as iaa


def get():
    def sometimes(aug): return iaa.Sometimes(0.5, aug)

    return iaa.Sequential(
        [
            # apply the following augmenters to most images
            iaa.Fliplr(0.5),  # horizontally flip 50% of all images
            iaa.Flipud(0.2),  # vertically flip 20% of all images
            # crop images by -5% to 10% of their height/width
            sometimes(iaa.CropAndPad(
                percent=(-0.05, 0.1),
                pad_mode=ia.ALL,
                pad_cval=(0, 255)
            )),
            sometimes(iaa.Affine(
                # scale images to 80-120% of their size, individually per axis
                scale={'x': (0.8, 1.2), 'y': (0.8, 1.2)},
                # translate by -20 to +20 percent (per axis)
                translate_percent={'x': (-0.2, 0.2), 'y': (-0.2, 0.2)},
                rotate=(-45, 45),  # rotate by -45 to +45 degrees
                shear=(-16, 16),  # shear by -16 to +16 degrees
                # use nearest neighbour or bilinear interpolation (fast)
                order=[0, 1],
                # if mode is constant, use a cval between 0 and 255
                cval=(0, 255),
                # use any of scikit-image's warping modes (see 2nd image from the top for examples)
                mode=ia.ALL
            )),
            # execute 0 to 5 of the following (less important) augmenters per image
            # don't execute all of them, as that would often be way too strong
            iaa.SomeOf((0, 5),
                       [
                # convert images into their superpixel representation
                sometimes(iaa.Superpixels(
                    p_replace=(0, 1.0), n_segments=(20, 200))),
                iaa.OneOf([
                    # blur images with a sigma between 0 and 3.0
                    iaa.GaussianBlur((0, 3.0)),
                    # blur image using local means with kernel sizes between 2 and 7
                    iaa.AverageBlur(k=(2, 7)),
                    # blur image using local medians with kernel sizes between 2 and 7
                    iaa.MedianBlur(k=(3, 11)),
                ]),
                iaa.Sharpen(alpha=(0, 1.0), lightness=(
                    0.75, 1.5)),  # sharpen images
                iaa.Emboss(alpha=(0, 1.0), strength=(
                    0, 2.0)),  # emboss images
                # search either for all edges or for directed edges,
                # blend the result with the original image using a blobby mask
                iaa.SimplexNoiseAlpha(iaa.OneOf([
                    iaa.EdgeDetect(alpha=(0.5, 1.0)),
                    iaa.DirectedEdgeDetect(
                        alpha=(0.5, 1.0), direction=(0.0, 1.0)),
                ])),
                # add gaussian noise to images
                iaa.AdditiveGaussianNoise(loc=0, scale=(
                    0.0, 0.05*255), per_channel=0.5),
                iaa.OneOf([
                    # randomly remove up to 10% of the pixels
                    iaa.Dropout((0.01, 0.1), per_channel=0.5),
                    iaa.CoarseDropout((0.03, 0.15), size_percent=(
                        0.02, 0.05), per_channel=0.2),
                ]),
                # invert color channels
                iaa.Invert(0.05, per_channel=True),
                # change brightness of images (by -10 to 10 of original value)
                iaa.Add((-10, 10), per_channel=0.5),
                # change hue and saturation
                iaa.AddToHueAndSaturation((-20, 20)),
                # either change the brightness of the whole image (sometimes
                # per channel) or change the brightness of subareas
                iaa.OneOf([
                    iaa.Multiply((0.5, 1.5), per_channel=0.5),
                    iaa.FrequencyNoiseAlpha(
                        exponent=(-4, 0),
                        first=iaa.Multiply((0.5, 1.5), per_channel=True),
                        second=iaa.ContrastNormalization((0.5, 2.0))
                    )
                ]),
                # improve or worsen the contrast
                iaa.ContrastNormalization((0.5, 2.0), per_channel=0.5),
                iaa.Grayscale(alpha=(0.0, 1.0)),
                # move pixels locally around (with random strengths)
                sometimes(iaa.ElasticTransformation(
                    alpha=(0.5, 3.5), sigma=0.25)),
                # sometimes move parts of the image around
                sometimes(iaa.PiecewiseAffine(scale=(0.01, 0.05))),
                sometimes(iaa.PerspectiveTransform(scale=(0.01, 0.1)))
            ],
                random_order=True
            )
        ],
        random_order=False
    )