Create QR-code in Python (PyQt)

Question

I'm currently using PyQt4 and qrcode4.0.4.

from PyQt4 import QtGui, QtCore
from PIL.ImageQt import ImageQt
import qrcode

class QRLabel(QtGui.QLabel):
    def __init__(self, text=""):
        super(QRLabel, self).__init__()
        self.setCode(text)

    def setCode(self, text=""):        
        self.text = text      
        qrImg = qrcode.make(text)
        imgQt = ImageQt(qrImg.convert("RGB"))   # keep a reference!
        pixm = QtGui.QPixmap.fromImage(imgQt)
        self.setPixmap(pixm.scaled(self.size(),QtCore.Qt.KeepAspectRatio))

As you can see, there are several hurdles to be passed before you get the image on your screen. The QR code starts as a RGBA PIL Image, it is converted to RGB, then to PIL ImageQt object, then to a QPixmap, which is then placed on a QLabel with a scaling fix.

If you don't explicitly store the imgQt reference, you get rubbish when you load the widget.

My question: is there anything I could do to improve this, as it seems there are so many conversions involved.

Answer 1

From the qrcode docs, it appears you can create your own image_factory, which might allow you to streamline the process.

You just need to subclass qrcode.image.base.BaseImage and reimplement the new_image, drawrect and save methods. This subclass could wrap a QImage and therefore eliminate the need for the PIL conversion step.

UPDATE:

Here's a demo that eliminates the PIL dependency (which is just as well, because I found PIL crashes with certain inputs):

from PyQt4 import QtGui, QtCore
import qrcode

class Image(qrcode.image.base.BaseImage):
    def __init__(self, border, width, box_size):
        self.border = border
        self.width = width
        self.box_size = box_size
        size = (width + border * 2) * box_size
        self._image = QtGui.QImage(
            size, size, QtGui.QImage.Format_RGB16)
        self._image.fill(QtCore.Qt.white)

    def pixmap(self):
        return QtGui.QPixmap.fromImage(self._image)

    def drawrect(self, row, col):
        painter = QtGui.QPainter(self._image)
        painter.fillRect(
            (col + self.border) * self.box_size,
            (row + self.border) * self.box_size,
            self.box_size, self.box_size,
            QtCore.Qt.black)

    def save(self, stream, kind=None):
        pass

class Window(QtGui.QWidget):
    def __init__(self):
        QtGui.QWidget.__init__(self)
        self.label = QtGui.QLabel(self)
        self.edit = QtGui.QLineEdit(self)
        self.edit.returnPressed.connect(self.handleTextEntered)
        layout = QtGui.QVBoxLayout(self)
        layout.addWidget(self.label)
        layout.addWidget(self.edit)

    def handleTextEntered(self):
        text = unicode(self.edit.text())
        self.label.setPixmap(
            qrcode.make(text, image_factory=Image).pixmap())

if __name__ == '__main__':

    import sys
    app = QtGui.QApplication(sys.argv)
    window = Window()
    window.setGeometry(500, 300, 200, 200)
    window.show()
    sys.exit(app.exec_())

Answer 2

You can also use PNG as an intermediate format and store it in memory using StringIO.

import qrcode
import StringIO

def set_qr_label(label, text):
    """
    set qrcode image on QLabel

    @param label: QLabel
    @param text: text for the QR code
    """
    buf = StringIO.StringIO()
    img = qrcode.make(text)
    img.save(buf, "PNG")
    label.setText("")
    qt_pixmap = QtGui.QPixmap()
    qt_pixmap.loadFromData(buf.getvalue(), "PNG")
    label.setPixmap(qt_pixmap)

Answer 3

This is ekhumoro answer working in pyqt5 in python3 hope it helps someone down the line.

from PyQt5 import QtWidgets, QtCore, QtGui
import qrcode

class Image(qrcode.image.base.BaseImage):
    def __init__(self, border, width, box_size):
        self.border = border
        self.width = width
        self.box_size = box_size
        size = (width + border * 2) * box_size
        self._image = QtGui.QImage(
            size, size, QtGui.QImage.Format_RGB16)
        self._image.fill(QtCore.Qt.white)

    def pixmap(self):
        return QtGui.QPixmap.fromImage(self._image)

    def drawrect(self, row, col):
        painter = QtGui.QPainter(self._image)
        painter.fillRect(
            (col + self.border) * self.box_size,
            (row + self.border) * self.box_size,
            self.box_size, self.box_size,
            QtCore.Qt.black)

    def save(self, stream, kind=None):
        pass

class Window(QtWidgets.QWidget):
    def __init__(self):
        QtWidgets.QWidget.__init__(self)
        self.label = QtWidgets.QLabel(self)
        self.edit = QtWidgets.QLineEdit(self)
        self.edit.returnPressed.connect(self.handleTextEntered)
        layout = QtWidgets.QVBoxLayout(self)
        layout.addWidget(self.label)
        layout.addWidget(self.edit)

    def handleTextEntered(self):
        text = self.edit.text()#text = unicode(self.edit.text())
        self.label.setPixmap(
            qrcode.make(text, image_factory=Image).pixmap())

if __name__ == '__main__':

    import sys
    app = QtWidgets.QApplication(sys.argv)
    window = Window()
    window.setGeometry(500, 300, 200, 200)
    window.show()
    sys.exit(app.exec_())

Answer 4

Great answer by mgmax but Python2 only. For Python3 use:

import qrcode
from io import BytesIO

def set_qr_label(label, text):
    """
    set qrcode image on QLabel

    @param label: QLabel
    @param text: text for the QR code
    """
    buf = BytesIO()
    img = qrcode.make(text)
    img.save(buf, "PNG")
    label.setText("")
    qt_pixmap = QtGui.QPixmap()
    qt_pixmap.loadFromData(buf.getvalue(), "PNG")
    label.setPixmap(qt_pixmap)