使用Tesseract 识别验证码

参考：
http://code.google.com/p/tesseract-ocr/
https://stackoverflow.com/questions/2363490/limit-characters-tesseract-is-looking-for
http://resources.infosecinstitute.com/case-study-cracking-online-banking-captcha-login-using-python/

1. 安装：

apt-get install tesseract-ocr

2. 预先处理图片，代码片段：

from PIL import Image
import os
import time

def crack(cap_name):
 
    img = Image.open(cap_name+'.JPEG')
    img = img.convert("RGB")
    pixdata = img.load()
 
    for y in xrange(img.size[1]):
        for x in xrange(img.size[0]):
            if pixdata[x, y][0] < 90:
                pixdata[x, y] = (0, 0, 0, 255)
    for y in xrange(img.size[1]):
        for x in xrange(img.size[0]):
            if pixdata[x, y][1] < 136:                 pixdata[x, y] = (0, 0, 0, 255)     for y in xrange(img.size[1]):         for x in xrange(img.size[0]):             if pixdata[x, y][2] > 0:
                pixdata[x, y] = (255, 255, 255, 255)
    ext = ".tif"
    img.save(cap_name + ext)

3. 使用tesseract命令识别图片：

tesseract imagename outbase [-l lang] [-psm N] [configfile ...]

引用

0 = Orientation and script detection (OSD) only.
1 = Automatic page segmentation with OSD.
2 = Automatic page segmentation, but no OSD, or OCR
3 = Fully automatic page segmentation, but no OSD. (Default)
4 = Assume a single column of text of variable sizes.
5 = Assume a single uniform block of vertically aligned text.
6 = Assume a single uniform block of text.
7 = Treat the image as a single text line.
8 = Treat the image as a single word.
9 = Treat the image as a single word in a circle.
10 = Treat the image as a single character.

4. 限制Tesseract搜索的字符
1）在tessdata/configs文件夹中创建一个新的配置文件
2）在配置文件中添加如下：

引用

tessedit_char_whitelist abcdefghijklmnopqrstuvwxyz 

3. 使用新建的配置文件调用tessdata命令。

5. 训练Tesseract识图能力
参考文章：
http://code.google.com/p/tesseract-ocr/wiki/TrainingTesseract2
http://code.google.com/p/tesseract-ocr/wiki/TrainingTesseract3