Using ImageMagick/ZBar to read QR codes

Question

I've got scanned image files that I perform some preprocessing on and get them looking something like this:

My phone's ZBar app can read this QR code fine, but zbarimg seems to be unable to figure it out. I've tried all sorts of things in ImageMagick to make it smoother (-smooth, -morphology) but even with slightly better-looking results, zbarimg still comes up blank.

Why would my phone's ZBar be so much better than my computer's (zbar-0.10)? Is there anything I can do to get zbarimg to read this successfully?

Answer 1

You can try morphological closing.

Python code:

# -*- coding: utf-8 -*-
import qrtools
import cv2
import numpy as np

imgPath = "Fdnm1.png"

img = cv2.imread(imgPath, 0)
kernel = np.ones((5, 5), np.uint8)
processed=cv2.morphologyEx(img, cv2.MORPH_CLOSE, kernel)
cv2.imwrite('test.png', processed)
d = qrtools.QR(filename='test.png')
d.decode()
print d.data

Result:

1MB24