Pivot property in pixels

[Vasily-van-Zaam]

Hey. I am using Sprite.fromImage.
I need to change the pivot property in pixels, but as I understand it cannot be done =(

var image = Sprite.fromImage(img);
image.pivot = Offset(0.5555, 0.5555);

if print the pivot, can this:

 Offset(0.5, 0.5)

Not even that Offset(0.5555, 0.5555);

These values ​​are rounded and do not refer to local coordinates, but refer to the height and width of the sprite.
How to make them relative to local coordinates?

I want it to be like this:

image.size = Size(50.0, 50.0);
image.position = Offset(250.0, 250.0); // center of canvas; canvas width and height == 500.0;
image.rotation = 90.0;
image.pivot = Offset(image.size.width/2, 100.0); 

Thanks.