Serializing QImage

In qt doc:
http://doc.qt.nokia.com/4.7/datastreamformat.html
is written:

Quote:

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... If you want control of the format, stream the image into a QBuffer (using QImageIO) and stream that.

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Can anyone explain me how can I "stream the image into a QBuffer (using QImageIO) and stream that"?(Maybe some minimal C++ example?)

Code:

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QBuffer buffer;
image.save(&buffer, "PNG");
QDataStream stream;
// ...
stream << buffer.data();

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