How to convert blob into byteArray in flask python?

Question

A customer sends a multipart file to me, I read it with:

    blob = request.files['file'].read()

I have a blob file in hand. Now I have to send this file with requests like open('file.png', 'rb'). How can I convert blob to something like rb mode. With open I could not open blob directly.

The below code did not work:

opened_file = open(request.files['file'], 'rb')

And I got the following error:

TypeError: coercing to Unicode: need string or buffer, FileStorage found

Is there a way to do that without saving it on file system? I send my requests to somewhere else:

files = dict({'file': byteArrayFile})
r = requests.post(self.url, files=files, headers=headers)

Thomas Orozco · Accepted Answer · 2015-02-02 08:44:54Z

1

request.files['file'] is already a file-like object (it's a FileStorage instance), so you can use that directly; you don't need to open it.

r = requests.post(self.url, files={"file": request.files["file"]}, headers=headers)

You can think of a file-like object as an open file. They behave the same way.

answered Feb 2, 2015 at 8:44

Thomas Orozco

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Amandeep Singh · Accepted Answer · 2015-06-26 18:28:27Z

1

try using

from PIL import Image
import requests
from io import BytesIO

response = requests.get(url)
img = Image.open(BytesIO(response.content))

it worked for me and for testing if you wish to have a look on the images try

img.show()

answered Jun 26, 2015 at 18:28

Amandeep Singh

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Charles Vogt · Accepted Answer · 2019-02-15 07:28:18Z

If your image is stored in a Blob format (i.e. in a database) you can use the same technique explained by Billal Begueradj to convert your image from Blobs to a byte array.

In my case, I needed my images where stored in a blob column in a db table:

def select_all_X_values(conn):
    cur = conn.cursor()
    cur.execute("SELECT ImageData from PiecesTable")    
    rows = cur.fetchall()    
    return rows

I then created a helper function to change my dataset into np.array:

X_dataset = select_all_X_values(conn)
imagesList = convertToByteIO(np.array(X_dataset))

def convertToByteIO(imagesArray):
    """
    # Converts an array of images into an array of Bytes
    """
    imagesList = []

    for i in range(len(imagesArray)):  
        img = Image.open(BytesIO(imagesArray[i])).convert("RGB")
        imagesList.insert(i, np.array(img))

    return imagesList

After this, I was able to use the byteArrays in my Neural Network.

plt.imshow(imagesList[0])

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