Convert captcha images so it can be read in tesseract

captcha.txt

# apt-get install -y imagemagick tesseract-ocr tesseract-ocr-eng python-pip
# pip install Image pytesseract
# python convert.py 2 captcha.png captcha-clean.png
# convert captcha-clean.png -resize 500 captcha-clean-big.png
# tesseract -c tessedit_char_whitelist=abcdefghijklmnopqrstuvwxyz1234567890 -psm 7 captcha-clean-big.png output
# cat output.txt

convert.py

#!/usr/bin/env python
## pip install Image
## python convert.py float(1-3) input.png output.png
from PIL import Image
import sys

chomp = float(sys.argv[1])
image = Image.open(sys.argv[2]).convert('1')
width, height = image.size
data = image.load()

for y in range(height):
    for x in range(width):

        if data[x, y] > 128:
            continue

        total = 0

        for c in range(x, width):

            if data[c, y] < 128:
                total += 1

            else:
                break

        if total <= chomp:
            for c in range(total):
                data[x + c, y] = 255

        x += total


for x in range(width):
    for y in range(height):

        if data[x, y] > 128:
            continue

        total = 0

        for c in range(y, height):

            if data[x, c] < 128:
                total += 1

            else:
                break

        if total <= chomp:
            for c in range(total):
                data[x, y + c] = 255

        y += total

image.save(sys.argv[3])