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 )

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

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

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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);

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

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or

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

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

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[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.