Argh, I haven't seen that you post in the qwt sub forum. I never have worked with it, but after some digging in the sources it seems to me that IO::Save support all formats QImageWriter::supportedImageFormats() provide. Is jpeg in it on your machine? And for a simple test load a jpeg file and save it right back with QImage and see if it works. If so there must be a problem in the qwt libraries, but then I am out.


EDIT: Ok, need to long to write; What's about QwtPlots in release mode?
EDIT: not my day: Seems you missing the plugin for release mode...