qTox/src/misc/qrwidget.cpp

#include "qrwidget.h"
#include <QPainter>
#include <QDebug>
#include <QBuffer>
#include <QImage>
#include "qrcodewindow.h"
#include "qrencode.h"

QRWidget::QRWidget(QWidget *parent) : QWidget(parent), data("0")
//Note: The encoding fails with empty string so I just default to something else. Use the setQRData() call to change this.
{
    //size of the qimage might be problematic in the future, but it works for me
    size.setWidth(480);
    size.setHeight(480);
    image = new QImage(size, QImage::Format_RGB32);
}

void QRWidget::setQRData(QString data)
{
    this->data = data;
    paintImage();    
}

QString QRWidget::getImageAsText()
{
    paintImage();
 	QByteArray ba;
 	QBuffer buffer(&ba);
 	buffer.open(QIODevice::WriteOnly);
    image->save(&buffer, "PNG"); // writes the image in PNG format inside the buffer
    
    QString iconBase64 = QString::fromLatin1(ba.toBase64().data());
    QString base64Image  = "<img width=\"350\" heigth=\"350\" src=\"data:image/png;base64," + iconBase64 +"\" />";
    
 	return QString(base64Image);
}

//http://stackoverflow.com/questions/21400254/how-to-draw-a-qr-code-with-qt-in-native-c-c
void QRWidget::paintImage()
{
    QPainter painter(image);
    //NOTE: I have hardcoded some parameters here that would make more sense as variables.
    QRcode *qr = QRcode_encodeString(data.toStdString().c_str(), 1, QR_ECLEVEL_L, QR_MODE_8, 0);
    
    if(0 != qr)
    {
        QColor fg("black");
        QColor bg("white");
        painter.setBrush(bg);
        painter.setPen(Qt::NoPen);
        painter.drawRect(0, 0, size.width(), size.height());
        painter.setBrush(fg);
        const int s = qr->width>0 ? qr->width : 1;
        const double w = width();
        const double h = height();
        const double aspect = w / h;
        const double scale = ((aspect > 1.0) ? h : w) / s;
        
        for(int y = 0; y < s; y++)
        {
            const int yy = y * s;
            for(int x = 0; x < s; x++)
            {
                const int xx = yy + x;
                const unsigned char b = qr->data[xx];
                if(b & 0x01)
                {
                    const double rx1 = x * scale,
                                 ry1 = y * scale;
                    QRectF r(rx1, ry1, scale, scale);
                    painter.drawRects(&r, 1);
                }
            }
        }
        QRcode_free(qr);
        painter.save();
    }
    else
    {
        QColor error("red");
        painter.setBrush(error);
        painter.drawRect(0, 0, width(), height());
        qDebug() << "QR FAIL: " << strerror(errno);
    }
    
    qr = 0;
}