In some image constructors, image data are currently auto-scaled. This
works by accident, as the device zoom used for auto scaling conforms to
the zoom of the image to be initialized.

However, to make this explicit, with this change the proper zoom is
passed to scale method. It also makes the autoScaleUp method in DPIUtil
obsolete and removes it.

Co-authored-by: Hannes Wellmann <wellmann.hannes1@gmx.net>