What is the best way to render a WSQ image in a QLabel

Question

I am trying to render a WSQ image in a QLabel in PyQt5. The WSQ image is in an xml file which is located in a zip file. Here is my approach:

import zipfile
import xml.etree.cElementTree as ET
import base64.b64decode as b64decode
from PyQt5 import QtGui, QtWidgets
...
try:
    with zipfile.ZipFile(zfilename) as src_zip:
        root = ET.fromstring(src_zip.open(xmlfilename).read())
except zipfile.BadZipFile as e:
    root = None
finger_prints = []
if root:
    for data in root.findall('.//Demographics/FingerData'):
        finger_prints.append(b64decode(data.find('FingerprintImage').text))
...
finger_data = finger_prints.pop()
pixmap = QtGui.QPixmap()
pixmap.loadFromData(finger_data, 'WSQ') # freezes
QtWidgets.QLabel().setPixmap(pixmap)

The second but last line causes the program to freeze/hang but if I do:

with file('/tmp/finger_print.wsq', 'wb') as f:
    f.write(finger_data)

I am able to view the image in a WSQ viewer. I understand Qt has plugins for different image formats, Is there an image plugin I am missing?

Thanks in advance for your help.

-Abraham.

Answer 1

The image formats Qt supports by default are:

 Format  Description                            Qt's support
 BMP     Windows Bitmap                         Read/write
 GIF     Graphic Interchange Format (optional)  Read
 JPG     Joint Photographic Experts Group       Read/write
 JPEG    Joint Photographic Experts Group       Read/write
 PNG     Portable Network Graphics              Read/write
 PBM     Portable Bitmap                        Read
 PGM     Portable Graymap                       Read
 PPM     Portable Pixmap                        Read/write
 XBM     X11 Bitmap                             Read/write
 XPM     X11 Pixmap                             Read/write

So you'll either have to write a custom Qt image plugin, or somehow convert the image data to one of the formats Qt understands.