问题
I managed to write numpy arrays to lmdb, howewer solution is far from perfection, but actually my X
is just jpg image, so my question is how to directly write jpeg file to lmdb?
Seems like pycaffe
doing similar thing but it use caffe specific Datum
and I need some general solution without dependencies.
回答1:
Here is example that write image as numpy array and directly as encoded jpg.
As we can see store jpg directly is more efficient in terms of storage.
du -sh * 184K temp.db 120K temp_jpg.db
import numpy as np
import lmdb
import cv2
n_samples= 2
def create_random_image(filename):
img= (np.random.rand(100,120,3)*255).astype(np.uint8)
cv2.imwrite(filename,img)
def write_lmdb(filename):
print 'Write lmdb'
lmdb_env = lmdb.open(filename, map_size=int(1e9))
X= cv2.imread('random_img.jpg')
y= np.random.rand(1).astype(np.float32)*10.0
for i in range(n_samples):
with lmdb_env.begin(write=True) as lmdb_txn:
lmdb_txn.put('X_'+str(i), X)
lmdb_txn.put('y_'+str(i), y)
print 'X.shape:',X.shape
print 'y:',y
def read_lmdb(filename):
print 'Read lmdb'
lmdb_env = lmdb.open(filename)
lmdb_txn = lmdb_env.begin()
lmdb_cursor = lmdb_txn.cursor()
#also can do it without iteration via txn.get('key1')?
n_counter=0
with lmdb_env.begin() as lmdb_txn:
with lmdb_txn.cursor() as lmdb_cursor:
for key, value in lmdb_cursor:
print key
if('X' in key):
print 'X.shape', np.fromstring(value, dtype=np.uint8).shape
if('y' in key):
print np.fromstring(value, dtype=np.float32)
n_counter=n_counter+1
print 'n_samples',n_counter
def write_lmdb_jpg(filename):
print 'Write lmdb'
lmdb_env = lmdb.open(filename, map_size=int(1e9))
X= cv2.imread('random_img.jpg')
y= np.random.rand(1).astype(np.float32)*10.0
for i in range(n_samples):
with lmdb_env.begin(write=True) as lmdb_txn:
lmdb_txn.put('X_'+str(i), cv2.imencode('.jpg', X)[1])
lmdb_txn.put('y_'+str(i), y)
print 'X.shape', cv2.imencode('.jpg', X)[1].shape
print 'y:',y
def read_lmdb_jpg(filename):
print 'Read lmdb'
lmdb_env = lmdb.open(filename)
lmdb_txn = lmdb_env.begin()
lmdb_cursor = lmdb_txn.cursor()
#also can do it without iteration via txn.get('key1')?
n_counter=0
with lmdb_env.begin() as lmdb_txn:
with lmdb_txn.cursor() as lmdb_cursor:
for key, value in lmdb_cursor:
print key
if('X' in key):
X_str= np.fromstring(value, dtype=np.uint8)
print 'X_str.shape', X_str.shape
X= cv2.imdecode(X_str, cv2.CV_LOAD_IMAGE_COLOR)
print 'X.shape', X.shape
if('y' in key):
print np.fromstring(value, dtype=np.float32)
n_counter=n_counter+1
print 'n_samples',n_counter
create_random_image('random_img.jpg')
#Write as numpy array
write_lmdb('temp.db')
read_lmdb('temp.db')
#Write as encoded jpg
write_lmdb_jpg('temp_jpg.db')
read_lmdb_jpg('temp_jpg.db')
来源:https://stackoverflow.com/questions/44280549/write-jpeg-file-directly-to-lmdb