basicsr/data/transforms.py

import cv2
import random
import numpy as np

def mod_crop(img, scale):
    """Mod crop images, used during testing.

    Args:
        img (ndarray): Input image.
        scale (int): Scale factor.

    Returns:
        ndarray: Result image.
    """
    img = img.copy()
    if img.ndim in (2, 3):
        h, w = img.shape[0], img.shape[1]
        h_remainder, w_remainder = h % scale, w % scale
        img = img[:h - h_remainder, :w - w_remainder, ...]
    else:
        raise ValueError(f'Wrong img ndim: {img.ndim}.')
    return img


def augment(imgs, hflip=True, rotation=True, flows=None, return_status=False):
    """Augment: horizontal flips OR rotate (0, 90, 180, 270 degrees).

    We use vertical flip and transpose for rotation implementation.
    All the images in the list use the same augmentation.

    Args:
        imgs (list[ndarray] | ndarray): Images to be augmented. If the input
            is an ndarray, it will be transformed to a list.
        hflip (bool): Horizontal flip. Default: True.
        rotation (bool): Ratotation. Default: True.
        flows (list[ndarray]: Flows to be augmented. If the input is an
            ndarray, it will be transformed to a list.
            Dimension is (h, w, 2). Default: None.
        return_status (bool): Return the status of flip and rotation.
            Default: False.

    Returns:
        list[ndarray] | ndarray: Augmented images and flows. If returned
            results only have one element, just return ndarray.

    """
    hflip = hflip and random.random() < 0.5
    vflip = rotation and random.random() < 0.5
    rot90 = rotation and random.random() < 0.5

    def _augment(img):
        if hflip:  # horizontal
            cv2.flip(img, 1, img)
        if vflip:  # vertical
            cv2.flip(img, 0, img)
        if rot90:
            img = img.transpose(1, 0, 2)
        return img

    def _augment_flow(flow):
        if hflip:  # horizontal
            cv2.flip(flow, 1, flow)
            flow[:, :, 0] *= -1
        if vflip:  # vertical
            cv2.flip(flow, 0, flow)
            flow[:, :, 1] *= -1
        if rot90:
            flow = flow.transpose(1, 0, 2)
            flow = flow[:, :, [1, 0]]
        return flow

    if not isinstance(imgs, list):
        imgs = [imgs]
    imgs = [_augment(img) for img in imgs]
    if len(imgs) == 1:
        imgs = imgs[0]

    if flows is not None:
        if not isinstance(flows, list):
            flows = [flows]
        flows = [_augment_flow(flow) for flow in flows]
        if len(flows) == 1:
            flows = flows[0]
        return imgs, flows
    else:
        if return_status:
            return imgs, (hflip, vflip, rot90)
        else:
            return imgs


def img_rotate(img, angle, center=None, scale=1.0):
    """Rotate image.

    Args:
        img (ndarray): Image to be rotated.
        angle (float): Rotation angle in degrees. Positive values mean
            counter-clockwise rotation.
        center (tuple[int]): Rotation center. If the center is None,
            initialize it as the center of the image. Default: None.
        scale (float): Isotropic scale factor. Default: 1.0.
    """
    (h, w) = img.shape[:2]

    if center is None:
        center = (w // 2, h // 2)

    matrix = cv2.getRotationMatrix2D(center, angle, scale)
    rotated_img = cv2.warpAffine(img, matrix, (w, h))
    return rotated_img

def data_augmentation(image, mode):
    """
    Performs data augmentation of the input image
    Input:
        image: a cv2 (OpenCV) image
        mode: int. Choice of transformation to apply to the image
                0 - no transformation
                1 - flip up and down
                2 - rotate counterwise 90 degree
                3 - rotate 90 degree and flip up and down
                4 - rotate 180 degree
                5 - rotate 180 degree and flip
                6 - rotate 270 degree
                7 - rotate 270 degree and flip
    """
    if mode == 0:
        # original
        out = image
    elif mode == 1:
        # flip up and down
        out = np.flipud(image)
    elif mode == 2:
        # rotate counterwise 90 degree
        out = np.rot90(image)
    elif mode == 3:
        # rotate 90 degree and flip up and down
        out = np.rot90(image)
        out = np.flipud(out)
    elif mode == 4:
        # rotate 180 degree
        out = np.rot90(image, k=2)
    elif mode == 5:
        # rotate 180 degree and flip
        out = np.rot90(image, k=2)
        out = np.flipud(out)
    elif mode == 6:
        # rotate 270 degree
        out = np.rot90(image, k=3)
    elif mode == 7:
        # rotate 270 degree and flip
        out = np.rot90(image, k=3)
        out = np.flipud(out)
    else:
        raise Exception('Invalid choice of image transformation')

    return out

def random_augmentation(*args):
    out = []
    flag_aug = random.randint(0,7)
    for data in args:
        if type(data) == list:
            out.append([data_augmentation(_data, flag_aug).copy() for _data  in data])
        else:
            out.append(data_augmentation(data, flag_aug).copy())
    return out