IplImage to QImage memory issue

[p3l-outrepid]

Dear forum,
I am using this method to change from IplImage captured by OpenCV library to a QImage to use QPainter class on and paint on it another QImage, now the problem is that I am using the method in a while loop which eats up my memory (over 1GB in mere seconds) and I can't find a way around it.

QImage MainWindow::IplImage2QImage(IplImage *iplImg)
{
    this->h = iplImg->height;
    this->w = iplImg->width;
    this->channels = iplImg->nChannels;
    this->qimg = new QImage(w, h, QImage::Format_ARGB32);
    this->data = iplImg->imageData;
 
    for (int y = 0; y < h; y++, data += iplImg->widthStep)
    {
    for (int x = 0; x < w; x++)
    {
    char r, g, b, a = 0;
    if (channels == 1)
    {
    r = data[x * channels];
    g = data[x * channels];
    b = data[x * channels];
    }
    else if (channels == 3 || channels == 4)
    {
    r = data[x * channels + 2];
    g = data[x * channels + 1];
    b = data[x * channels];
    }
 
    if (channels == 4)
    {
    a = data[x * channels + 3];
    qimg->setPixel(x, y, qRgba(r, g, b, a));
    }
    else
    {
    qimg->setPixel(x, y, qRgb(r, g, b));
    }
    }
    }
    return *qimg;
}

QImage MainWindow::IplImage2QImage(IplImage *iplImg)
{
    this->h = iplImg->height;
    this->w = iplImg->width;
    this->channels = iplImg->nChannels;
    this->qimg = new QImage(w, h, QImage::Format_ARGB32);
    this->data = iplImg->imageData;

    for (int y = 0; y < h; y++, data += iplImg->widthStep)
    {
    for (int x = 0; x < w; x++)
    {
    char r, g, b, a = 0;
    if (channels == 1)
    {
    r = data[x * channels];
    g = data[x * channels];
    b = data[x * channels];
    }
    else if (channels == 3 || channels == 4)
    {
    r = data[x * channels + 2];
    g = data[x * channels + 1];
    b = data[x * channels];
    }

    if (channels == 4)
    {
    a = data[x * channels + 3];
    qimg->setPixel(x, y, qRgba(r, g, b, a));
    }
    else
    {
    qimg->setPixel(x, y, qRgb(r, g, b));
    }
    }
    }
    return *qimg;
}

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now that's the method itself and the while loop for looping on frames is the following

while(i<numFrames){
    if(i<(SelectedFrame+numofFrames)){
        cvGrabFrame(capture);
        img2=cvRetrieveFrame(capture);
        qimage=this->IplImage2QImage(img2);
        QPainter p(&qimage);
        p.drawImage(xcoordinate, ycoordinate, input , 0,0,-1,-1,Qt::AutoColor);
        img3=this->qtToCv(&(qimage));
        cvWriteFrame(writer,img3);
        i++;
        img2=0;
        img3=0;
        p.end();
        qimage=QImage();
    }
    else {
      cvGrabFrame(capture);
      img2=cvRetrieveFrame(capture);
      cvWriteFrame(writer,img2);
      i++;
      img2=0;
    }
    ui->progressBar_2->setValue(i);
    }

while(i<numFrames){
    if(i<(SelectedFrame+numofFrames)){
        cvGrabFrame(capture);
        img2=cvRetrieveFrame(capture);
        qimage=this->IplImage2QImage(img2);
        QPainter p(&qimage);
        p.drawImage(xcoordinate, ycoordinate, input , 0,0,-1,-1,Qt::AutoColor);
        img3=this->qtToCv(&(qimage));
        cvWriteFrame(writer,img3);
        i++;
        img2=0;
        img3=0;
        p.end();
        qimage=QImage();
    }
    else {
      cvGrabFrame(capture);
      img2=cvRetrieveFrame(capture);
      cvWriteFrame(writer,img2);
      i++;
      img2=0;
    }
    ui->progressBar_2->setValue(i);
    }

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now I know that the problem is with the method because I commented everything else and only the calling of the method caused the memory overload. All I need is for another method (or a change in this method) to ensure that not too much memory is used while applying it.
Thanks a lot and best regards,
p3l

[high_flyer]

The reason for the memory consumption is that you are only allocating memory, and never free it.
There is no need to allocate a new QImage for each iteration.
Allocate the QImage once, and reuse it.

QImage MainWindow::IplImage2QImage(IplImage *iplImg)
{
    this->h = iplImg->height;
    this->w = iplImg->width;
    this->channels = iplImg->nChannels;
    if(this->qimg == NULL); //don't forget to set qimg = NULL in the constructor, and delete it in the destructor (or give it a parent)
         this->qimg = new QImage(w, h, QImage::Format_ARGB32);
    this->data = iplImg->imageData;
.....
}

QImage MainWindow::IplImage2QImage(IplImage *iplImg)
{
    this->h = iplImg->height;
    this->w = iplImg->width;
    this->channels = iplImg->nChannels;
    if(this->qimg == NULL); //don't forget to set qimg = NULL in the constructor, and delete it in the destructor (or give it a parent)
         this->qimg = new QImage(w, h, QImage::Format_ARGB32);
    this->data = iplImg->imageData;
.....
}

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