Only read part of a binary file

Rory_1

I'm a Qt beginner and would like a little direction to help me get started.

I want to draw an embedded jpeg from a raw camera file in an imageLabel. I have done this successfully by editing a raw file in a hex editor, eliminating all of the file except the embedded jpeg and then tested using this code:

QFile file("D:/Rory/Pictures/test2.nef");
file.open(QIODevice::ReadOnly);
QByteArray buf = file.readAll();
QImage *image = new QImage;
image->loadFromData(buf);
imageLabel->setPixmap(QPixmap::fromImage(*image));
...

I want to populate buf with only the embedded jpeg from the NEF raw image file. I need to find the file offset for the first instance of hex FFD8 and then read until hex FFD9. I think I should iterate through the file using qFile::seek to find the offsets for FFD8 and FFD9, use qFile::pos to move to FFD8 and qFile::read(the offset difference between FFD8 and FFD9).

Am I on the right path? And if so, is there any sample code to help me?

Many thanks in advance.

t3685

@Rory_1

You can also consider using QDataStream:

http://doc.qt.io/qt-5/qdatastream.html

Rory_1

Thanks, QDataStream looks promising.