htmlsnap.cpp

#include "htmlsnap.h"
#include <QPainter>
#include <QDebug>
#include <QWebFrame>

HtmlSnap::HtmlSnap()
{
    connect(&page, SIGNAL(loadFinished(bool)), this, SLOT(render()));
}

void HtmlSnap::loadHtml(char* html)
{
    qDebug() << "loading HTML";
    page.mainFrame()->setHtml(QString(html), QUrl());
}

void HtmlSnap::render()
{
    qDebug() << "rendering";
    page.setViewportSize(page.mainFrame()->contentsSize());
    QImage image(page.viewportSize(), QImage::Format_ARGB32);
    QPainter painter(&image);

    page.mainFrame()->render(&painter);
    painter.end();

    QImage thumbnail = image.scaled(400, 400);
    thumbnail.save("thumbnail.png");

    qDebug() << "done";

    emit finished();
}

htmlsnap.h

#ifndef HTMLSNAP_H
#define HTMLSNAP_H

#include <QObject>
#include <QWebPage>

class HtmlSnap : public QObject
{

    Q_OBJECT

    QWebPage page;
public:
    HtmlSnap();
    void loadHtml(char* html);

private slots:
    void render();

signals:
    void finished();

};

#endif // HTMLSNAP_H

main.cpp

#include <QApplication>
#include "htmlsnap.h"

int main(int argc, char *argv[])
{
    QApplication app(argc, argv);

    HtmlSnap snap;
    QObject::connect(&snap, SIGNAL(finished()), &app, SLOT(quit()));

    snap.loadHtml("<h1>Hello World</h1>");

    return app.exec();
}