Computationally inexpensive (lossy) method of screenshot and/or movie?

[Mr_Cloud]

Hello,

I'm trying to sequentially grab screenshots and send them to a label located on the GUI. The purpose is to eventually write a program which records the screen.

I've successfully achieved this with QPixmap's grabWindow, only it is quite slow and not very framerate friendly (I would love some 20-30fps). I've also noticed that grabWindow hides the mouse before taking a screenshot, which is a great feature usually but doesn't interest me. Also, seeing as it is a QPixmap feature, it is safe to assume that lossless (png?) screenshots are taken, which means 6meg or more per 1080p screen.

Here is my code so far:

//mw.h
#include <QtGui/QMainWindow>
#include <QApplication>
#include <QPixmap>
#include <QWidget>
#include <QtGui>
#include <QTimer>
 
namespace Ui
{
    class mw;
}
 
class mw : public QMainWindow
{
    Q_OBJECT
 
public:
    mw(QWidget *parent = 0);
    ~mw();
    QTimer *derp;
 
public slots:
    void process();
 
private:
    Ui::mw *ui;
};

//mw.h
#include <QtGui/QMainWindow>
#include <QApplication>
#include <QPixmap>
#include <QWidget>
#include <QtGui>
#include <QTimer>

namespace Ui
{
    class mw;
}

class mw : public QMainWindow
{
    Q_OBJECT

public:
    mw(QWidget *parent = 0);
    ~mw();
    QTimer *derp;

public slots:
    void process();

private:
    Ui::mw *ui;
};

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//mw.cpp
using namespace std;
 
mw::mw(QWidget *parent)
    : QMainWindow(parent), ui(new Ui::mw)
{
    ui->setupUi(this);
 
    derp=new QTimer;
    connect(derp,SIGNAL(timeout()),this,SLOT(process()));
    derp->start(50); //20fps
}
 
mw::~mw()
{
    delete ui;
}
 
void mw::process(){
    ui->label->setPixmap(QPixmap::grabWindow(QApplication::desktop()->winId()).scaled(ui->label->size(),Qt::KeepAspectRatio,Qt::SmoothTransformation));
}

//mw.cpp
using namespace std;

mw::mw(QWidget *parent)
    : QMainWindow(parent), ui(new Ui::mw)
{
    ui->setupUi(this);

    derp=new QTimer;
    connect(derp,SIGNAL(timeout()),this,SLOT(process()));
    derp->start(50); //20fps
}

mw::~mw()
{
    delete ui;
}

void mw::process(){
    ui->label->setPixmap(QPixmap::grabWindow(QApplication::desktop()->winId()).scaled(ui->label->size(),Qt::KeepAspectRatio,Qt::SmoothTransformation));
}

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What would be an alternative to lossless, CPU-intensive screenshots? Would Qt support taking jpg screenshots instead of png? Or perhaps it could be done with OpenGL somehow? Perhaps even QImageWriter?

Thanks in advance.


Regards,
Mr_Cloud

[anda_skoa]

A screenshot is just pixel data, it is not in any image storage format.
You can decide which format to save to.

http://qt-project.org/doc/qt-5/QImag...ng-image-files

Cheers,
_