There is no parameter for speed/rate

[mariolourobert]

A parameter for speed/rate, or, in an another point of view, the z-index of the image, may be a good improvement ?

[bruckmatthew]

This should be an easy fix. A rate property needs to be included and insterted to the code here at line 210 in parallax_image.dart:

Alignment alignment;
if (_scrollPosition.axis == Axis.vertical) {
double value = rate*(_position.dy / _screenSize.height - 0.5).clamp(-1.0, 1.0);
alignment = new Alignment(0.0, value);
} else {
double value = rate*(_position.dx / _screenSize.width - 0.5).clamp(-1.0, 1.0);
alignment = new Alignment(value, 0.0);
}

I've played aroud with changing the values in the package code and negative values work well.

Apologies for not just doing it as I've not edited plugins before. Granted i gave it a try, but it came up with errors. @pulyaevskiy