Qt C++ video4linux kamera képe

Ezzel próbálkozom... van egy
videovidget.cpp:

#include "videowidget.h"


videowidget::videowidget(QWidget *parent) :
QWidget(parent)
{
setAutoFillBackground(true);
}

void videowidget::paintEvent(QPaintEvent *event) {
try{
QPainter painter(this);

if(!img.isNull()){
painter.drawImage(QPoint(0,0), img);
}
}catch(...){}
}

videowidget.h:

#ifndef VIDEOWIDGET_H
#define VIDEOWIDGET_H


#include < QWidget >
#include < QPainter >

class videowidget : public QWidget
{
Q_OBJECT
public:
explicit videowidget(QWidget *parent = 0);
QImage img;

protected:
void paintEvent(QPaintEvent *event);

signals:

public slots:

};

#endif // VIDEOWIDGET_H

A mainwindow.cpp-ban van egy onStopCapture(), ami tökéletes lenne:

#include "mainwindow.h"
#include < QString >
#include < QImage >
...
void MainWindow::onStopCapture()
{
t->devam=false;
//QImage img;
QString savepath = "/path/to/pic1.png";
QByteArray ba;
QBuffer buffer(&ba);
buffer.open(QIODevice::WriteOnly);
video->img.save(&buffer, &savepath, "PNG");
}


Erre azt mondja a fordító:

mainwindow.cpp:79: error: no matching function for call to 'QImage::save(QBuffer*, QString*, const char [4])'
video->img.save(&buffer, &savepath, "PNG");
--------------------------------------------------------------------^

Mit rontottam el?

--
G.