Both PNG and JPEG support is now included with Qt. PNG is always available, and JPEG is available if the installer of Qt enabled it. Hence, the ImageIO extension is no longer required.
When installing Qt, add "-system-jpeg" when you run "configure". Notes that this requires that you have JpegLib 6.0 or better installed on your system It is also tested with libjpeg.so.6.0.1. See ftp.uu.net for the official sources. See FTP Search for other sources. See the JPEG FAQ for more information.