Bad Svg in QGraphicsView [Qt 5.5]

GGAllin

Hello everyone
I've a problem with some svg icons and retina monitor..
they looks perfect when are scaled at 100% but if are under 100% they looks really bad
here's my code

#include <QApplication>
#include <QDebug>
#include <QWidget>
#include <QGraphicsView>
#include <QGraphicsSvgItem>
#include <QSvgRenderer>

int main(int argc, char **argv)
{
    QApplication app(argc, argv);

    QGraphicsScene scene;
    QGraphicsView view(&scene);

    QString pic(argv[1]);
    QSvgRenderer renderer(pic);

    int w = 58;
    int h = 58;
    int hdpi = 2;
    QImage image(w*hdpi, h*hdpi, QImage::Format_ARGB32);
    QPainter painter(&image);
    renderer.render(&painter);

    QGraphicsPixmapItem pix( QPixmap::fromImage(image));
    //pix.setScale(1.0/hdpi); // 100%
    pix.setScale(0.4/hdpi);
    scene.addItem(&pix);

    view.show();
    return app.exec();
}

here the result
link text

and at 100%
link text

are there something wrong in my code ?
Help me please! ;-)

Tnks.
GG

mrjj

hi
have you tried with
painter.setRenderHint(QPainter::Antialiasing);
or
painter.setRenderHint(QPainter::HighQualityAntialiasing);
to see if u can get it to smooth it ?

kshegunov

@GGAllin
You're scaling a raster image, so don't do that. Instead provide a smaller image for the QSvgRenderer to render onto. For example, what's wrong with this?

    QImage image(0.4 * w, 0.4* h, QImage::Format_ARGB32);
    QPainter painter(&image);
    renderer.render(&painter);

    QGraphicsPixmapItem pix( QPixmap::fromImage(image));
    scene.addItem(&pix);

The idea is that the last thing you do is render the vector data to raster, so you can actually keep the quality.

GGAllin

@mrjj

@mrjj said:

hi
have you tried with
painter.setRenderHint(QPainter::Antialiasing);
or
painter.setRenderHint(QPainter::HighQualityAntialiasing);
to see if u can get it to smooth it ?

@kshegunov said:

@GGAllin
You're scaling a raster image, so don't do that. Instead provide a smaller image for the QSvgRenderer to render onto. For example, what's wrong with this?
    QImage image(0.4 * w, 0.4* h, QImage::Format_ARGB32);
    QPainter painter(&image);
    renderer.render(&painter);

    QGraphicsPixmapItem pix( QPixmap::fromImage(image));
    scene.addItem(&pix);
The idea is that the last thing you do is render the vector data to raster, so you can actually keep the quality.

@mrjj said:

hi
have you tried with
painter.setRenderHint(QPainter::Antialiasing);
or
painter.setRenderHint(QPainter::HighQualityAntialiasing);
to see if u can get it to smooth it ?

Nothing change with QPainter::HighQualityAntialiasing or QPainter::Antialiasing

mrjj

ok.
good to know.
Was just a shot.

so @kshegunov way should do it :)

GGAllin

Yeah!```
QImage image(0.4 * w, 0.4* h, QImage::Format_ARGB32);
QPainter painter(&image);
renderer.render(&painter);

QGraphicsPixmapItem pix( QPixmap::fromImage(image));
scene.addItem(&pix);


works perfect!
Many thanks to all!!

GGAllin

better result using fill(Qt::Transparent)

    int w = svgSize.width();
    int h = svgSize.height();
    int hdpi = docView->devicePixelRatio() <2 ? 1: 2;
    QSvgRenderer renderer("icon.svg");
    QImage image(scaleF*w*hdpi,scaleF* h*hdpi, QImage::Format_ARGB32);
    image.fill(Qt::TransparentMode);
    QPainter painter(&image);
    painter.setRenderHint(QPainter::HighQualityAntialiasing);
    renderer.render(&painter);
    QGraphicsPixmapItem* pix =new QGraphicsPixmapItem(QPixmap::fromImage(image));
    pix->setScale(1.0/hdpi);

kshegunov

@GGAllin
Forgive my ignorance, but how is this:

QImage image(scaleF * w * hdpi, scaleF * h * hdpi, QImage::Format_ARGB32);
QGraphicsPixmapItem* pix = new QGraphicsPixmapItem(QPixmap::fromImage(image));
pix->setScale(1.0 / hdpi);

different from this:

QImage image(scaleF * w, scaleF * h, QImage::Format_ARGB32);
QGraphicsPixmapItem* pix = new QGraphicsPixmapItem(QPixmap::fromImage(image));

The whole point of using vector graphics is not to scale raster images, but to render directly to the correct sizes. isn't it? So why do you insist on rendering a larger image and then scaling it down?