问题
I've extracted features using caffe, which generates a .mdb file. Then I'm trying to read it using Python and display it as a readable number.
import lmdb
lmdb_env = lmdb.open('caffefeat')
lmdb_txn = lmdb_env.begin()
lmdb_cursor = lmdb_txn.cursor()
for key, value in lmdb_cursor:
print str(value)
This prints out a very long line of unreadable, broken characters.
Then I tried printing int(value), which returns the following:
ValueError: invalid literal for int() with base 10: '\x08\x80 \x10\x01\x18\x015\x8d\x80\xad?5'
float(value) gives the following:
ValueError: could not convert string to float:? 5????5
Is this a problem with the lmdb file itself, or does it have to do with conversion of data type?
回答1:
Here's the working code I figured out
import caffe
import lmdb
lmdb_env = lmdb.open('directory_containing_mdb')
lmdb_txn = lmdb_env.begin()
lmdb_cursor = lmdb_txn.cursor()
datum = caffe.proto.caffe_pb2.Datum()
for key, value in lmdb_cursor:
datum.ParseFromString(value)
label = datum.label
data = caffe.io.datum_to_array(datum)
for l, d in zip(label, data):
print l, d
回答2:
If you have encoded images in lmdb
, you'll probably see this error when using @ytrewq's code
ValueError: total size of new array must be unchanged
Use this function instead:
import caffe
import lmdb
import PIL.Image
from StringIO import StringIO
import numpy as np
def read_lmdb(lmdb_file):
cursor = lmdb.open(lmdb_file, readonly=True).begin().cursor()
datum = caffe.proto.caffe_pb2.Datum()
for _, value in cursor:
datum.ParseFromString(value)
s = StringIO()
s.write(datum.data)
s.seek(0)
yield np.array(PIL.Image.open(s)), datum.label
Example:
lmdb_dir = '/save/jobs/20160613-125532-958f/train_db/'
for im, label in read_lmdb(lmdb_dir):
print label, im
来源:https://stackoverflow.com/questions/33117607/caffe-reading-lmdb-from-python