Qt resize image with best quality

Question

Can anyone help me resize an image in qt without making the image pixelated. Here's my code. the result is not as good as the original quality..thanks...

QImage img(name);
QPixmap pixmap;
pixmap = pixmap.fromImage(img.scaled(width,height,Qt::IgnoreAspectRatio,Qt::FastTransformation));
QFile file(folder+"/"+name);
file.open(QIODevice::WriteOnly);
pixmap.save(&file, "jpeg",100);
file.close();

Wreathe

Do you shrink or extend the image? If you extend the image you will always have a "big" quality loss, since there is no more information for the new space than in the original image. Nevertheless every resize will be a loss in quality. There are quite a few algorithms for this all having different pros and cons. – Whispering

Did you try using Qt::SmoothTransformation instead of Qt::FastTransformation? – Millham

Answer 1

You have to pass Qt::SmoothTransformation transformation mode to the scaled function like:

QImage img(name);
QPixmap pixmap;
pixmap = pixmap.fromImage(img.scaled(width,height,Qt::IgnoreAspectRatio,Qt::SmoothTransformation));
QFile file(folder+"/"+name);
file.open(QIODevice::WriteOnly);
pixmap.save(&file, "jpeg",100);
file.close();

Crosse