CODEWITHSUNDEEP
qtqt5
DalJit Maan
DalJit Maan

Reputation: 11

Converting Text to Image (like PNG or JPEG)

I need help in writing my static text to image file without using "QApplication app(argc, argv);" in main(). My version of QT is 5.12.2.

Currently I'm able to do this with the below code:

int main(int argc, char *argv[])
{
QApplication app(argc, argv);
QCoreApplication::addLibraryPath("./plugins");
QString imagePath(QStringLiteral("./images/output/testOutput1.png"));
QImage image(500, 400, QImage::Format_RGB888);

image.fill(Qt::red);

QPainter painter;

if (!painter.begin(&image))
    return;

painter.setPen(QPen(Qt::black));
painter.setFont(QFont("Times", 12, QFont::Bold));
painter.drawText(image.rect(), Qt::AlignCenter, "writing text on image");
painter.end();

image.save(imagePath);

return 0;
}

I'm trying to get a similar type solution which does not uses "QApplication app(argc, argv);" in my code.

Currently if I remove the deceleration of "QApplication app(argc, argv);" my code crashes at "painter.drawText(...);".

Upvotes: 0

Views: 560

Answers (1)

Matteo Italia
Matteo Italia

Reputation: 126777

The most you can do is to exchange the QApplication for a QGuiApplication (thus avoiding the useless dependency from the QtWidgets module).

Qt initializes most of its static/global stuff inside the bowels of QCoreApplication (for QtCore stuff)/QGuiApplication (for QtGui stuff)/QApplication (for QtWidgets stuff); each derives from the other, so if you have a QApplication you already have all the stuff from Gui and Core.

The font engine (and other paint-related stuff) is initialized inside the QGuiApplication constructor, as hinted in QFont documentation

Note that a QGuiApplication instance must exist before a QFont can be used.

so you are not going to paint without instantiating it (or a class derived from it).

Upvotes: 1

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