Book cover test

cover.py

import cv2 as cv
import numpy as np
import os.path
import sys


def is_useful_cover(f):
    # intended for thumbnail images, width = 180 pixels
    img = cv.imread(f)
    img = cv.Canny(img, 100, 200)
    edginess = np.mean(img, axis=1)
    n = np.std(edginess)
    return n >= 13


def write_report(filenames):
    print('''
<style>
img { vertical-align: top; }
.useful { border: 10px solid blue; }
.not { border: 10px solid red; }
</style>
''')
    for filename in filenames:
        name = os.path.splitext(os.path.basename(filename))[0]
        url = 'https://archive.org/services/img/%s' % name
        useful = is_useful_cover(filename)
        print('<img src="{url}" alt="{name}" class="{klass}">'.format(
            filename=filename,
            url=url,
            name=name,
            klass='useful' if useful else 'not'))


if __name__ == '__main__':
    write_report(sys.argv[1:])