Just give your QImage the desired size. The SVG renderer will scale to fit the whole image.
#include <QApplication>
#include <QSvgRenderer>
#include <QPainter>
#include <QImage>
// In your .pro file:
// QT += svg
int main(int argc, char **argv)
{
// A QApplication instance is necessary if fonts are used in the SVG
QApplication app(argc, argv);
// Load your SVG
QSvgRenderer renderer(QString("./svg-logo-h.svg"));
// Prepare a QImage with desired characteritisc
QImage image(500, 200, QImage::Format_ARGB32);
image.fill(0xaaA08080); // partly transparent red-ish background
// Get QPainter that paints to the image
QPainter painter(&image);
renderer.render(&painter);
// Save, image format based on file extension
image.save("./svg-logo-h.png");
}
This will create an 500×200 PNG image from the passed in SVG file.
Example output with an SVG image from the SVG logos page:
