Erlang/Elixir: 使用 OpenCV, Python 搭建图片缩略图服务器

这篇文章是在OSX上测试和运行的的, Ubuntu下的安装和配置请移步到这里

应用程序进程树, 默认 Poolboy 中初始化10个用于处理图片的 Python 工作进程(Worker)

首先安装OpenCV需要的工具包

 

 

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ruby -e "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/master/install)" brew install python brew tap homebrew/science brew install opencv sudo pip install numpy sudo pip install matplotlib

使用 Homebrew 的 Python 版本, 而不是 Mac OS X 系统自带的 Python

 

 

1	alias python='/usr/local/bin/python'

创建 Elixir 项目

 

 

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➜  mix new opencv_thumbnail_server --sup * creating README.md * creating .gitignore * creating mix.exs * creating config * creating config/config.exs * creating lib * creating lib/opencv_thumbnail_server.ex * creating test * creating test/test_helper.exs * creating test/opencv_thumbnail_server_test.exs   Your Mix project was created successfully. You can use "mix" to compile it, test it, and more:       cd opencv_thumbnail_server     mix test   Run "mix help" for more commands.

Elixir 模块

 

 

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require Logger defmodule OpencvThumbnailServer do   use Application   def start(_type, _args) do     Logger.info "Start opencv thumbnail server"     OpencvThumbnailServer.Supervisor.start_link()   end end

 

 

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defmodule OpencvThumbnailServer.Supervisor do   use Supervisor     <a href="http://www.jobbole.com/members/chkconfig">@config</a> Application.get_env :opencv_thumbnail_server, :settings     def start_link() do     Supervisor.start_link(__MODULE__, [], name: {:global,__MODULE__})   end     def init([]) do     pool_options = @config[:poolboy]     {_, name} = pool_options[:name]     children = [       :poolboy.child_spec(name, pool_options, @config[:module_name])     ]     supervise(children, strategy: :one_for_all, max_restarts: 1000, max_seconds: 3600)   end end

 

 

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defmodule OpencvThumbnailServer.Worker do   use GenServer   <a href="http://www.jobbole.com/members/chkconfig">@config</a> Application.get_env(:opencv_thumbnail_server, :settings)     def start_link(python_module) do     GenServer.start_link(__MODULE__, python_module, [])   end     def call_python(worker, function, args) do     GenServer.call(worker, {:call_python, function, args}, 10_000)   end     def init(python_module) do     IO.puts "Start worker"     {:ok, pid} = :python.start_link([       {:python_path, @config[:python_path]},       {:python, @config[:python]}     ])     state = {python_module, pid}     {:ok, state}   end     def handle_call({:call_python, function, args}, _from, state) do     {module, pid} = state     result = :python.call(pid, module, function, args)     reply = {:ok, result}     {:reply, reply, state}   end     def handle_call(_request, _from, state) do     {:stop, :error, :bad_call, state}   end     def handle_info(_msg, {module,py_pid}) do     {:stop, :error, {module,py_pid}}   end     def terminate(_reason, {_, py_pid}) do     :python.stop(py_pid)     :ok   end end

图像处理

获取宽高

 

 

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# -*- coding: utf-8 -*-   import urllib2 as urllib import numpy as np import cv2     def load_image_url(url):     resp = urllib.urlopen(url)     buf = resp.read()     return buf     def load_image_file(filename):     image = cv2.imdecode(filename, cv2.IMREAD_COLOR)     return image   def get_photo_sizes():     return [         [160, 160],         [320, 320],         [640, 640],         [1060, 1060],         [1280, 1280]     ] def show(buf):     # print buf     # x = cv2.imdecode(image, cv2.IMREAD_COLOR)     # d = cv2.cvtColor(c, cv2.COLOR_RGB2BGR)     np_ndarray = np.fromstring(buf, dtype=np.uint8)     x = cv2.imdecode(np_ndarray, cv2.IMREAD_UNCHANGED)     return cv2.imshow('NBA Image', x)   def write(buf):     nparray = np.fromstring(buf, dtype=np.uint8)     img = cv2.imdecode(nparray, cv2.IMREAD_UNCHANGED)     return cv2.imwrite('/tmp/imwrite.png', img)   # def get_dimension(): #     url = 'http://img1.gtimg.com/16/1601/160106/16010642_1200x1000_0.jpg' #     resp = urllib.urlopen(url) #     buf = resp.read() #     x = np.fromstring(buf, dtype=np.uint8) #     img = cv2.imdecode(x, cv2.IMREAD_UNCHANGED) #     # height = np.size(img, 0) #     # width = np.size(img, 1) #     height, width = image.shape[:2] #     return (width, height)   def get_dimension(buffer):     # 把原始的二进制图片数据转换为NpArray     nparray = np.fromstring(buffer, dtype=np.uint8)     # 把 nparray 转换为 opencv 的图像格式     image = cv2.imdecode(nparray, cv2.IMREAD_UNCHANGED)     height, width = image.shape[:2]     return (width, height)   def convert_color():     url = 'http://ww3.sinaimg.cn/mw690/6941baebgw1epzcuv9vmxj20me0hy0u1.jpg'     resp = urllib.urlopen(url)     buf = resp.read()     x = np.fromstring(buf, dtype=np.uint8)     img = cv2.imdecode(x, cv2.IMREAD_UNCHANGED)   if __name__ == '__main__':     get_dimension()

在 Erlang 和 Python 之间传输二进制数据

Erlang 的binary()数据类型和 Python 之间的映射关系, 在Python 2.x 中二进制数据类型为 str() 表示, Python 3.x 中为 bytes()

buf = resp.read(), 其中变量 buf 的类型为

在 Elixir 我们看的如下的值

 

 

 

 

 

Python

 

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{:ok, <<255, 216, 255, 224, 0, 16, 74, 70, 73, 70, 0, 1, 1, 1, 0, 72,       0, 72, 0, 0, 255, 219, 0, 67, 0, 8, 6, 6, 7, 6, 5, 8, 7, 7, 7,       9, 9, 8, 10, 12, 20, 13, 12, 11, 11, 12, 25, 18, 19, ...>>}

调用 Python 函数

 

 

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{:ok, data} = OpencvThumbnailServer.Api.load_image_url("https://segmentfault.com/img/bVwhAW") OpencvThumbnailServer.Api.get_dimension(data) {:ok, {800, 431}}

创建 Python 模块

之前的 Python 图像处理模块可以组织到一个项目中单独维护. 这里使用工具 cookiecutter创建 Python 一个基本的项目骨架, 用于实现缩略图的功能

cookiecutter 可以通过多种方式安装, 包括pip, easy_install, conda, brew 厦门电动叉车

 

 

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pip install cookiecutter easy_install cookiecutter conda install -c https://conda.binstar.org/pydanny cookiecutter brew install cookiecutter(Mac OS X)

目录结构

 

 

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➜  opencv_thumbnail git:(master) tree . ├── AUTHORS.rst ├── CONTRIBUTING.rst ├── HISTORY.rst ├── LICENSE ├── MANIFEST.in ├── Makefile ├── README.rst ├── build │   ├── bdist.macosx-10.11-x86_64 │   └── lib │       └── opencv_thumbnail │           ├── __init__.py │           └── opencv_thumbnail.py ├── dist │   └── opencv_thumbnail-0.1.0-py2.7.egg ├── docs │   ├── Makefile │   ├── authors.rst │   ├── conf.py │   ├── contributing.rst │   ├── history.rst │   ├── index.rst │   ├── installation.rst │   ├── make.bat │   ├── readme.rst │   └── usage.rst ├── opencv_thumbnail │   ├── __init__.py │   ├── __init__.pyc │   ├── opencv_thumbnail.py │   └── opencv_thumbnail.pyc ├── opencv_thumbnail.egg-info │   ├── PKG-INFO │   ├── SOURCES.txt │   ├── dependency_links.txt │   ├── not-zip-safe │   └── top_level.txt ├── requirements_dev.txt ├── setup.cfg ├── setup.py ├── tests │   ├── __init__.py │   └── test_opencv_thumbnail.py ├── tox.ini └── travis_pypi_setup.py   9 directories, 36 files

API实现

调用需要从 Poolboy 池中取出一个工作进程, 并调用工作进程的call_python, 进程使用完成后返回 Poolboy 进程池, 这里封装一下以简化调用

 

 

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defmodule OpencvThumbnailServer.Api do   alias OpencvThumbnailServer.Worker     def get_dimension(data) do     worker = :poolboy.checkout(:opencv_thumbnail_server_pool)     {w, h} = Worker.call_python(worker, :get_dimension, [data])     :poolboy.checkin(:opencv_thumbnail_server_pool, worker)     {w, h}   end     def load_image_url(url) do     worker = :poolboy.checkout(:opencv_thumbnail_server_pool)     image_bin = Worker.call_python(worker, :load_image_url, [url])     :poolboy.checkin(:opencv_thumbnail_server_pool, worker)     image_bin   end end

源码

https://github.com/developerworks/opencv_thumbnail_server

参考资料

利用Python和OpenCV将URL直接转换成OpenCV格式
How to read raw png from an array in python opencv?
Install OpenCV for Python on Mac OS X
Installing scikit-image
How can i read an image from an internet url in python cv2 , scikit image and mahotas
Using Elixir, erlport with Python 2.7.9, receiving an arity error
How to read image from in memory buffer (StringIO) or from url with opencv python library
Python OpenCV convert image to byte string?