de_transform.py

import cv2

import numpy as np

def get_random_structure(size):
    # The provided model is trained with 
    #   choice = np.random.randint(4)
    # instead, which is a bug that we fixed here
    choice = np.random.randint(1, 5)

    if choice == 1:
        return cv2.getStructuringElement(cv2.MORPH_RECT, (size, size))
    elif choice == 2:
        return cv2.getStructuringElement(cv2.MORPH_ELLIPSE, (size, size))
    elif choice == 3:
        return cv2.getStructuringElement(cv2.MORPH_ELLIPSE, (size, size//2))
    elif choice == 4:
        return cv2.getStructuringElement(cv2.MORPH_ELLIPSE, (size//2, size))

def random_dilate(seg, min=3, max=10):
    size = np.random.randint(min, max)
    kernel = get_random_structure(size)
    seg = cv2.dilate(seg,kernel,iterations = 1)
    return seg

def random_erode(seg, min=3, max=10):
    size = np.random.randint(min, max)
    kernel = get_random_structure(size)
    seg = cv2.erode(seg,kernel,iterations = 1)
    return seg

def compute_iou(seg, gt):
    intersection = seg*gt
    union = seg+gt
    return (np.count_nonzero(intersection) + 1e-6) / (np.count_nonzero(union) + 1e-6)

def perturb_seg(gt, iou_target=0.6):
    h, w = gt.shape
    seg = gt.copy()

    _, seg = cv2.threshold(seg, 127, 255, 0)

    # Rare case
    if h <= 2 or w <= 2:
        print('GT too small, returning original')
        return seg

    # Do a bunch of random operations
    for _ in range(250):
        for _ in range(4):
            lx, ly = np.random.randint(w), np.random.randint(h)
            lw, lh = np.random.randint(lx+1,w+1), np.random.randint(ly+1,h+1)

            # Randomly set one pixel to 1/0. With the following dilate/erode, we can create holes/external regions
            if np.random.rand() < 0.25:
                cx = int((lx + lw) / 2)
                cy = int((ly + lh) / 2)
                seg[cy, cx] = np.random.randint(2) * 255

            if np.random.rand() < 0.5:
                seg[ly:lh, lx:lw] = random_dilate(seg[ly:lh, lx:lw])
            else:
                seg[ly:lh, lx:lw] = random_erode(seg[ly:lh, lx:lw])

        if compute_iou(seg, gt) < iou_target:
            break

    return seg