安装：
sudo apt-get install imagemagick
ImageMagick 是一个用来创建、编辑、合成图片的软件。它可以读取、转换、写入多种格式的图片。图片切割、颜色替换、各种效果的应用，图片的旋转、组合，文本，直线， 多边形，椭圆，曲线，附加到图片伸展旋转。ImageMagick是免费软件：全部源码开放，可以自由使用，复制，修改，发布。支持大多数的操作系统。
检测是否支持指定格式 identify -list format | grep PNG
sudo apt-get install tesseract-ocr
OCR(Optical Character Recognition):光学字符识别,是指对图片文件中的文字进行分析识别，获取的过程。
Tesseract：开源的OCR识别引擎，初期Tesseract引擎由HP实验室研发，后来贡献给了开源软件业，后经由Google进行改进，消除bug，优化，重新发布
gem install mini_magick
mini_magick 是用ruby对ImageMagick命令的封装,可以这样简单的使用
image = MiniMagick::Image.open("input.jpg") image.resize "100x100" image.write "output.jpg"
image = MiniMagick::Image.open("http://www.google.com/images/logos/logo.png") image.resize "5x5" image.format "gif" image.write "localcopy.gif"
https://github.com/minimagick/minimagick
gem install rtesseract
rtesseract对了tesseract-ocr进行了封装
识别验证码：
RTesseract.new(img.path).to_s
在 ubuntu12.04上安装如果出现如下问题，请安装 libmagickwand-dev
sudo apt-get install libmagickwand-dev
zhaol-a@ubuntu:~/gcj_project$ gem install rtesseract
/usr/share/ruby-rvm/rubies/ruby-1.9.3-p392/lib/ruby/1.9.1/yaml.rb:56:in `<top (required)>':
It seems your ruby installation is missing psych (for YAML output).
To eliminate this warning, please install libyaml and reinstall your ruby.
Building native extensions. This could take a while...
ERROR: Error installing rtesseract:
ERROR: Failed to build gem native extension.
/usr/share/ruby-rvm/rubies/ruby-1.9.3-p392/bin/ruby extconf.rb
checking for Ruby version >= 1.8.5... yes
checking for gcc... yes
checking for Magick-config... no
Can't install RMagick 2.13.2. Can't find Magick-config in /usr/share/ruby-rvm/gems/ruby-1.9.3-p392/bin:/usr/share/ruby-rvm/gems/ruby-1.9.3-p392@global/bin:/usr/share/ruby-rvm/rubies/ruby-1.9.3-p392/bin:/usr/share/ruby-rvm/gems/ruby-1.9.3-p392/bin:/usr/share/ruby-rvm/gems/ruby-1.9.3-p392@global/bin:/usr/share/ruby-rvm/rubies/ruby-1.9.3-p392/bin:/usr/share/ruby-rvm/bin:/usr/lib/lightdm/lightdm:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games
*** extconf.rb failed ***
Could not create Makefile due to some reason, probably lack of
necessary libraries and/or headers. Check the mkmf.log file for more
details. You may need configuration options.
Provided configuration options:
--with-opt-dir
--without-opt-dir
--with-opt-include
--without-opt-include=${opt-dir}/include
--with-opt-lib
--without-opt-lib=${opt-dir}/lib
--with-make-prog
--without-make-prog
--srcdir=.
--curdir
--ruby=/usr/share/ruby-rvm/rubies/ruby-1.9.3-p392/bin/ruby
使用mechanize，nokogiri进行数据抓取，验证码识别的例子：
#encoding: utf-8
require 'mechanize'
require 'nokogiri'
require 'spreadsheet'
require 'rtesseract'
require 'mini_magick'
require 'open-uri'
require 'uri'
require 'iconv'
require 'active_support/all'
#调整图片的大小来提高图片的识别准确度
def parse_img_to_str(img_url)
img = MiniMagick::Image.open(img_url)
img.resize '200%x200%' # 放大
img.colorspace("GRAY") # 灰度化
img.monochrome # 去色
str = RTesseract.new(img.path).to_s # 识别
File.unlink(img.path) # 删除临时文件
if str.nil?
return nil
else
return str.strip.to_f
end
end
#使用异常处理，可以减少因为网络延迟导致timeout的问题，但是不能完全避免
#分析请求的url, 和参数
def get_json_data(agent, url, params)
begin
response = agent.post(url, params)
json_data = JSON.parse(response.body)
return json_data
rescue
retry # restart from beginning
end
end
p "waiting................."
agent = Mechanize.new
agent.open_timeout = 15
file_path = File.dirname(__FILE__)user
#用户登陆要抓取的网站后，用firefox导出cookies信息到cookies.txt
cookies_file_path = "/home/username/project/cookies.txt"
#导入cookie信息，跳过登陆
agent.cookie_jar.load_cookiestxt(cookies_file_path)
#抓取年份信息的例子
title_params = {"area" => area,"province" => "北京"}
years_info = get_json_data(agent, gov_mat_ttile_url, title_params)["result"]
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