How to resize an image while scrolling down?

Link to visualizing picture - could not add image here because I do not have needed reputation level.

I have tried to visualize my problem in the picture above.

I have an ImageView in a ScrollView.
I have modified the start position so a part of the ImageView start above the screen, ScrollView.srollTo(0, [value > 0]).

The issue is:
I want to show the bitmap center cropped when the scroll view is on start position ie. like 90% of the bitmap. While scrolling down the ScrollView to top position (scrollY = 0) I want to decrease the image crop level and when reaching the top the whole image shall be visible, no cropping.