摘要：這篇文章是在上測試和運行的的下的安裝和配置請移步到這里應用程序進程樹默認啟動時初始化個用于處理圖片的工作進程首先安裝需要的工具包使用的版本而不是系統自帶的創建項目模塊圖像處理獲取寬高把原始的二進制圖片數據轉換為把轉換為的圖

這篇文章是在OSX上測試和運行的的, Ubuntu下的安裝和配置請移步到這里

應用程序進程樹, 默認啟動 Poolboy 時, 初始化10個用于處理圖片的 Python 工作進程(Worker)

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 系統自帶的 Python

alias python="/usr/local/bin/python"

?  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 模塊

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

defmodule OpencvThumbnailServer.Supervisor do
  use Supervisor

  @config 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

defmodule OpencvThumbnailServer.Worker do
  use GenServer
  @config 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

獲取寬高

# -*- 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):
    # 把原始的二進制圖片數據轉換為NpArray
    nparray = np.fromstring(buffer, dtype=np.uint8)
    # 把 nparray 轉換為 opencv 的圖像格式
    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()

Erlang 的binary()數據類型和 Python 之間的映射關系, 在Python 2.x 中二進制數據類型為 str() 表示, Python 3.x 中為 bytes()

buf = resp.read(), 其中變量 buf 的類型為

在 Elixir 我們看到變量 buf 的值為:

{: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, ...>>}

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

之前的 Python 圖像處理模塊可以組織到一個項目中多帶帶維護. 這里使用工具 cookiecutter 創建 Python 一個基本的項目骨架, 用于實現縮略圖的功能

cookiecutter 可以通過多種方式安裝, 包括pip, easy_install, conda, brew

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

目錄結構

?  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

調用需要從 Poolboy 池中取出一個工作進程, 并調用工作進程的call_python, 進程使用完成后返還給 Poolboy 進程池, 這里對調用過程封裝一下, 以簡化使用.

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

https://github.com/developerworks/opencv_thumbnail_server

利用Python和OpenCV將URL直接轉換成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?