QPrinter prints only in GrayScale (option setColorMode enabled)

[locke]

Hi everyone,

I'm trying to print a QwtPlot, but it is only printed in gray scale. Here is the code:

QPrinter printer;
 
            printer.setOrientation(QPrinter::Landscape);
 
            printer.setOutputFormat(QPrinter::NativeFormat);
            printer.setColorMode(QPrinter::Color);
 
            QPrintDialog *dialog = new QPrintDialog(&printer, 0);  
            dialog->setWindowTitle(tr("Print Plot: ") + myPlotName);
            if (dialog->exec() != QDialog::Accepted) return;
 
            QPainter painter;
            painter.begin(&printer);
            painter.setPen( Qt::black);
            painter.setFont(QFont("Arial", 12));
 
            QwtPlotPrintFilter filter;
            my_plot->print(&painter, QRect(100,100,800,600), filter);
            QString dateLabel = "Produced on: " + QDate::currentDate().toString() + " at: " + QTime::currentTime().toString();
            painter.drawText(QRect(0,0, 600, 600), dateLabel);
            painter.end();

QPrinter printer;
     
            printer.setOrientation(QPrinter::Landscape);
 
            printer.setOutputFormat(QPrinter::NativeFormat);
            printer.setColorMode(QPrinter::Color);

            QPrintDialog *dialog = new QPrintDialog(&printer, 0);  
            dialog->setWindowTitle(tr("Print Plot: ") + myPlotName);
            if (dialog->exec() != QDialog::Accepted) return;

            QPainter painter;
            painter.begin(&printer);
            painter.setPen( Qt::black);
            painter.setFont(QFont("Arial", 12));

            QwtPlotPrintFilter filter;
            my_plot->print(&painter, QRect(100,100,800,600), filter);
            QString dateLabel = "Produced on: " + QDate::currentDate().toString() + " at: " + QTime::currentTime().toString();
            painter.drawText(QRect(0,0, 600, 600), dateLabel);
            painter.end();

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The curious thing, if I export it as PDF:

printer.setOutputFormat(QPrinter::PdfFormat);
 printer.setOutputFileName(filename);

printer.setOutputFormat(QPrinter::PdfFormat);
 printer.setOutputFileName(filename);

To copy to clipboard, switch view to plain text mode 

It is correctly exported, in color.

Any idea please??

Thanks in advance