QImage::invertPixels may produce invalid data after inversions of
images with premultiplied alpha, because the inverted colors will be
larger than the alpha.
This patch converts any image with a premultiplied alpha channel to
ARGB32 before inverting the pixels, and then back to the original
format after the inversion.
Support is added for correct inversion of RGBA8888 and RGB30 formats.
Task-number: QTBUG-39901
Change-Id: Ief24c55f495e67ef2ad6429b5b418d02963a64dd
Reviewed-by: Gunnar Sletta <gunnar.sletta@jollamobile.com>
d8dc664b94