Export Plot Results to PDF

[theofthe]

In my application, I have multiple tabs, in each tab, there is a plot diagram (QwtPlot object). I need to export the plot diagram inside each tab into a single pdf file. Is there any "append" option in QwtPlotRenderer class I can use? If not, is there any file format supported by qwt?

[Uwe]

A convenient way for one plot to one file is QwtPlotRenderer::renderDocument().


QwtPlotRenderer renderer;
for( int i = 0; i < numTabs; i++ )
{
renderer.renderDocument( plot(i), fileName(i), "pdf", QSizeF( 300, 200 ), 85 );
// renderer.renderDocument( plot(i), fileName(i), QSizeF( 300, 200 ), 85 ); // guesses the format from the fileName extension
}
As PDF ( like SVG ) is a vector graphics format the resolution parameter only matters, when your plot contains raster graphics ( f.e. a spectrogram ). For raster graphic formats ( see QImageWriter::supportedImageFormats() ) a higher resolution means higher quality.

QwtPlotRenderer offers several convenience methods how to set up a QPainter, but in the end they all call:


virtual void QwtPlotRenderer::render( QwtPlot *, QPainter *, const QRectF &rect ) const;

So when none of the convenience methods match your use case you can always setup your painter individually and call QwtPlotRenderer::render() from application code.
Examples might be if you want to render several plots to the same page, or create a PDF document for all plots, where you want to have each plot on a single page.

When trying to set up the painter in application code looking at the implementation of QwtPlotRenderer ( qwt_plot_renderer.cpp ) might help.

Uwe

[theofthe]

Thanks again Uwe. Your suggestion works fine.

Btw, may be if QwtPlotRenderer class could provide the append function and page adjustment functions in the future, it would be greater?