image conversion speed?

[tommy]

I have a choice to either make a QPixmap out of a file or out of a QImage.
Which is faster?

Which of the below functions is faster?


QPixmap QPixmap::fromImage ( const QImage & image, Qt::ImageConversionFlags flags = Qt::AutoColor ) [static]

QBitmap::QBitmap ( const QString & fileName, const char * format = 0 )


I try to achieve the following:
1) extract QImage and QPixmap from an image file (jpg)
2) resize both of them to a certain size
What is the best pipeline for doing that? Should I:
a) first make both from the file and then resize them both, or
b) make one of them (and which one first?), then resize it and convert into the other ??

[tommy]

I guess my my main question is this:
If you had to vote, which one do you think is faster:



QPixmap pic;
pic=pic.load(filename);

or


QPixmap pic;
QImage image;
pic=pic.fromImage(image, Qt::AutoColor);

[ChristianEhrlicher]

According to the qt-source (you could also take a look by your own), QPixmap::load() uses QImage and QPixmap::fromImage() to convert it to a QPixmap. So it should be faster to get the QPixmap from the QImage.