painter->setRasterOp()

how to change setRasterop to setcompatibility option in qt4 or we have to use rubberband instead of compositionmode option

QRubberband is a convenience class if you want to show a selection. And compositionmodes have replaced the rasterops. Look at http://doc.qt.nokia.com/4.7-snapshot...itionMode-enum to find the one you are looking for.

Otherwise showing code to people and explaining the context you are (I'm trying to ...) will always help.