compressing numpy array with zlib + base64 [python]

Question

I'm trying to send a numpy array through the python requests module to a flask server.

First, I compressed the numpy array with zlib, then used base64 to encode the data, then tried to decode and decompress but it's not working.

import numpy as np 
import base64
import zlib
import requests

frame = np.random.randint(0,255,(5,5,3)) # dummy rgb image
# compress
data = zlib.compress(frame)
print('compressed')
print(data)
print(len(data))
print(type(data))

data = base64.b64encode(frame)
print('b64 encoded')
print(data)
print(len(data))
print(type(data))

data = base64.b64decode(data)
print('b64 decoded')
print(data)
print(len(data))
print(type(data))

data = zlib.decompress(data)
print('b64 decoded')

I'm getting the following error:

Traceback (most recent call last):
  File "client.py", line 26, in <module>
    data = zlib.decompress(data)
zlib.error: Error -3 while decompressing data: incorrect header check

Roy2012 · Accepted Answer · 2020-05-27 11:01:28Z

1

data = base64.b64encode(frame) should be

b64encode (data)

You’re accidentally encoding the wrong thing ...

answered May 27, 2020 at 11:01

Roy2012

12.7k3 gold badges28 silver badges38 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

Zabir Al Nazi Nabil · Accepted Answer · 2020-05-27 11:13:32Z

0

I just realized after considering the extra length for base64 encoded string, I can completely get rid of it.

So, the following code snippet does what I need, it compresses the numpy array, then I can get the original array back without using base64. It gets rid of some of the overhead.

import numpy as np 
import base64
import zlib
import requests

frame = np.random.randint(0,255,(5,5,3)) # dummy rgb image
# compress
data = zlib.compress(frame)
print('compressed')
print(data)
print(len(data))
print(type(data))


data = zlib.decompress(data)
print('b64 decoded')


data = np.frombuffer(data, dtype=np.uint8)

print(data)
print(type(data))

answered May 27, 2020 at 11:13

Zabir Al Nazi Nabil

11.3k4 gold badges38 silver badges71 bronze badges

Collectives™ on Stack Overflow

compressing numpy array with zlib + base64 [python]

2 Answers 2

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related