Getting TypeError when trying to convert in-memory image to base64 string?

Question

I'm getting URL through POST via DAJAX.

The URL is then passed into the function below. A TypeError is thrown.

I do not want to save the 'img' to disk and then reopen it to do the conversion.

I'm not sure what else to try so I figured I as the world. Thanks for the help in advance.

def getqrcode(link):
    bsettings = Bitcoinsettings.objects.get(pk=1)
    qr = qrcode.QRCode(version=1, error_correction=qrcode.constants.ERROR_CORRECT_H, box_size=bsettings.qrcodesize , border=5,)
    qr.add_data(link)
    qr.make(fit=True)
    img = qr.make_image()
    output = StringIO.StringIO()
    img.save(output, 'GIF')
    contents = output.getvalue()
    data = base64.b64encode(open(contents,'rb').read())
    data = "data:image/png;base64," + data
    output.close()
    img = []
    return data

TypeError: file() argument 1 must be encoded string without NULL bytes, not str

Here is the ajax.py code.

from torgap.bitcoin.bitcoin import getqrcode
from dajaxice.decorators import dajaxice_register
from dajax.core import Dajax
@dajaxice_register
def getimage(request, image):
    try:
        dajax = Dajax()
        link = image
        image = getqrcode(link)
        dajax.assign('#qrcode', 'src', image)
        return dajax.json()
    except Exception as e: 
        print e 

Answer 1

I'm not sure you understand what returns ouput.getvalue() since you are trying to read the file again with

data = base64.b64encode(open(contents,'rb').read())

but in the line above contents already contains a string representation of the image file. And it is almost sure that here is where are hidden the annoying NULL bytes that file() complains about.

Try change the line above by:

 data = base64.b64encode(contents)

Also you can give a look at StringIO reference.