boundary_modification.py

import cv2
import numpy as np
import random
import math

try:
    from util.de_transform import perturb_seg
except:
    from de_transform import perturb_seg


def modify_boundary(image, regional_sample_rate=0.1, sample_rate=0.1, move_rate=0.0, iou_target = 0.8):
    # modifies boundary of the given mask.
    # remove consecutive vertice of the boundary by regional sample rate
    # ->
    # remove any vertice by sample rate
    # ->
    # move vertice by distance between vertice and center of the mask by move rate. 
    # input: np array of size [H,W] image
    # output: same shape as input
    
    # get boundaries
    if int(cv2.__version__[0]) >= 4:
        contours, _ = cv2.findContours(image, cv2.RETR_LIST, cv2.CHAIN_APPROX_NONE)
    else:
        _, contours, _ = cv2.findContours(image, cv2.RETR_LIST, cv2.CHAIN_APPROX_NONE)

    #only modified contours is needed actually. 
    sampled_contours = []   
    modified_contours = [] 

    for contour in contours:
        if contour.shape[0] < 10:
            continue
        M = cv2.moments(contour)

        #remove region of contour
        number_of_vertices = contour.shape[0]
        number_of_removes = int(number_of_vertices * regional_sample_rate)
        
        idx_dist = []
        for i in range(number_of_vertices-number_of_removes):
            idx_dist.append([i, np.sum((contour[i] - contour[i+number_of_removes])**2)])
            
        idx_dist = sorted(idx_dist, key=lambda x:x[1])
        
        remove_start = random.choice(idx_dist[:math.ceil(0.1*len(idx_dist))])[0]
        
       #remove_start = random.randrange(0, number_of_vertices-number_of_removes, 1)
        new_contour = np.concatenate([contour[:remove_start], contour[remove_start+number_of_removes:]], axis=0)
        contour = new_contour
        

        #sample contours
        number_of_vertices = contour.shape[0]
        indices = random.sample(range(number_of_vertices), int(number_of_vertices * sample_rate))
        indices.sort()
        sampled_contour = contour[indices]
        sampled_contours.append(sampled_contour)

        modified_contour = np.copy(sampled_contour)
        if (M['m00'] != 0):
            center = round(M['m10'] / M['m00']), round(M['m01'] / M['m00'])

            #modify contours
            for idx, coor in enumerate(modified_contour):

                change = np.random.normal(0,move_rate) # 0.1 means change position of vertex to 10 percent farther from center
                x,y = coor[0]
                new_x = x + (x-center[0]) * change
                new_y = y + (y-center[1]) * change

                modified_contour[idx] = [new_x,new_y]
        modified_contours.append(modified_contour)
        

    #draw boundary
    gt = np.copy(image)
    image = np.zeros_like(image)

    modified_contours = [cont for cont in modified_contours if len(cont) > 0]
    if len(modified_contours) == 0:
        image = gt.copy()
    else:
        image = cv2.drawContours(image, modified_contours, -1, (255, 0, 0), -1)

    image = perturb_seg(image, iou_target)
    
    return image