* Note: This is not version 17.x.x Previews of PPM files, with a low max value, are dark. They seem to not honor the ppm, or maybe any netpbm format's, max value. In my tests this is true for plain ppm (magic number P3) as well as raw (P6) types, but may be true for all netpbm library types.
Please check if this is indeed fixed with Qt 5.9. See https://bugreports.qt.io/browse/QTBUG-18262