mongodb python image 图像存储读取

最近做一些数据库调研的工作，目标是实现影像更快的入库、出库、查询，并实现并行访问等操作。

将结果总结成一个mongoImg类，也算是小结吧。

 '''
 Created on 2013-8-6
 class mongoInsert
 @author: tree
 '''
 __metaclass__ = type

 import os
 from pymongo.database import Database
 import time
 import gridfs

 class mongoImg(object):
     """mongoInsert is a class for inserting document

     """
     def __init__(self, database, dir):
         """Create a new instance of :class:mongoInsert
         :Parameters:
           - `database`: database to use
           - `dir` : directory of document
           """
         if not isinstance(database, Database):
             raise TypeError("database must be an instance of Database")
         if len(dir) < 1:
             raise TypeError("dir must be an string of directory")

 #         self.__con = Connection()
         self.__imgdb = database
         self.__imgfs = gridfs.GridFS (self.__imgdb)
         self.__dir = dir
         self.__filelist=[]

     #save filepath in list.txt
     def __dirwalk(self,topdown=True):
         """traverse the documents of self.__dir and save in self.__filelist
         """
         sum=0
         self.__filelist.clear()

         for root,dirs,files in os.walk(self.__dir,topdown):
             for name in files:
                 sum+=1
                 temp=os.path.join(root,name)
                 self.__filelist.append(temp)
         print(sum)

     #insert image
     def insert(self):
         """insert images in mongodb
         """
         self.__dirwalk()

         tStart = time.time()
         for fi in self.__filelist:
             with open (fi,'rb') as myimage:
                 data=myimage.read()
                 self.__imgfs.put(data, content_type = "jpg", filename =fi)

         tEnd =time.time ()
         print ("It cost %f sec" % (tEnd - tStart))

     #get image by filename
     def getbyname(self,filename,savepath):
         """get img from mongdb by filename
         """
         if len(savepath) < 1:
             raise TypeError("dir must be an string of directory")
         dataout=self.__imgfs.get_version(filename)
         try:
             imgout=open(savepath,'wb')
             data=dataout.read()
             imgout.write(data)
         finally:
             imgout.close()
         

使用示例：也可以将数据库连接写在类内部

 from pymongo import Connection
 import mongoImg

 filedir=r'D:\image'
 con = Connection()
 db = con.imgdb
 imgmongo=mongoImg.mongoImg(db,filedir)
 imgmongo.insert()

感觉mongodb存储影像切片还是蛮快的，1w多个图片，大约100-200秒左右。

tip：

gridfs.GridFS.put 函数

put(data, **kwargs)
Put data in GridFS as a new file.

Equivalent to doing:

try:
    f = new_file(**kwargs)
    f.write(data)
    finally
f.close()

在存储读取图像时，犯了低级错误，将open得到的file实例当做数据存储，读取的时候怎么也读不出数据。。。囧

另外以字节流形式读取图像数据比较适合。

pipe = open('/dev/input/js0','rb')

如果以str形式存储的话，可能会出现UnicodeDecodeError错误，貌似是因为图像数据有些超出了python默认编码的存储区间。

ps：初学python 数据库操作也忘得差不多 欢迎大家批评和指正~