I'm not sure I understand your question. I assume you are doing something along the lines of:

import base64

with open("yourfile.ext", "rb") as image_file:
    encoded_string = base64.b64encode(image_file.read())

You have to open the file first of course, and read its contents - you cannot simply pass the path to the encode function.

Edit: Ok, here is an update after you have edited your original question.

First of all, remember to use raw strings (prefix the string with 'r') when using path delimiters on Windows, to prevent accidentally hitting an escape character. Second, PIL's Image.open either accepts a filename, or a file-like (that is, the object has to provide read, seek and tell methods).

That being said, you can use cStringIO to create such an object from a memory buffer:

import cStringIO
import PIL.Image

# assume data contains your decoded image
file_like = cStringIO.StringIO(data)

img = PIL.Image.open(file_like)
img.show()

Python 3

import base64
from io import BytesIO

buffered = BytesIO()
image.save(buffered, format="JPEG")
img_str = base64.b64encode(buffered.getvalue())

Python 2

import base64
import cStringIO

buffer = cStringIO.StringIO()
image.save(buffer, format="JPEG")
img_str = base64.b64encode(buffer.getvalue())

The simplest approach would be: Array to json to base64:

import json
import base64

data = [0, 1, 0, 0, 83, 116, -10]
dataStr = json.dumps(data)

base64EncodedStr = base64.b64encode(dataStr.encode('utf-8'))
print(base64EncodedStr)

print('decoded', base64.b64decode(base64EncodedStr))

Prints out:

>>> WzAsIDEsIDAsIDAsIDgzLCAxMTYsIC0xMF0=
>>> ('decoded', '[0, 1, 0, 0, 83, 116, -10]')  # json.loads here !

... another option could be using bitarray module.

You can encode the RGB directly to jpg in memory and create a base64 encoding of this.

jpg_img = cv2.imencode('.jpg', img)
b64_string = base64.b64encode(jpg_img[1]).decode('utf-8')

Full example:

import cv2
import base64
img = cv2.imread('test_image.jpg')
jpg_img = cv2.imencode('.jpg', img)
b64_string = base64.b64encode(jpg_img[1]).decode('utf-8')

The base 64 string should be decodable with https://codebeautify.org/base64-to-image-converter

I believe since numpy.arrays support the buffer protocol, you just need the following:

processed_string = base64.b64encode(img)

So, for example:

>>> encoded = b"aGVsbG8sIHdvcmxk"
>>> img = np.frombuffer(base64.b64decode(encoded), np.uint8)
>>> img
array([104, 101, 108, 108, 111,  44,  32, 119, 111, 114, 108, 100], dtype=uint8)
>>> img.tobytes()
b'hello, world'
>>> base64.b64encode(img)
b'aGVsbG8sIHdvcmxk'
>>>