get_mask.py

import argparse

import numpy as np
import matplotlib.pyplot as plt

from matplotlib.widgets import LassoSelector
from matplotlib.path import Path
from skimage import color


parser = argparse.ArgumentParser(description="mask an image")
parser.add_argument("image")
args = parser.parse_args()

fn = args.image
im = color.rgb2gray(plt.imread(fn)/255.)
fout = ''.join(fn.split('.')[:-1]) + "_mask"
imh, imw = im.shape

plt.figure()
plt.imshow(im, cmap='gray')

def onselect(verts):
    path = Path(verts)

    x = np.arange(imw)
    y = np.arange(imh)
    xx, yy = np.meshgrid(x, y)
    points = list(zip(np.ravel(xx), np.ravel(yy)))

    inside = np.reshape(path.contains_points(points), (imh, imw))
    plt.figure()
    plt.imshow(inside)
    plt.show()
    np.save(fout, inside)


lasso = LassoSelector(plt.gca(), onselect)
plt.show()