I don't know how to translate a position to it's relative position to an object's rotation and position.
I have created a script to move the sprite based on a stored x and y position. I do not know how to reverse this script and have it work for getting the relative position when I place it down.
The script on the bottom will accurately work as I rotate the map sprite I am using, but I have been unsuccesful in usung the position on the stage to create the 'x' and 'y' variables.
Custom block definitions:
Change y by cos(direction of sprite one) * the pixel length from the rotation point that you want the y anchored to
Do the same for x with sin(direction of sprite one) * the same pixel length.
You are changing the original point by these values, or, mathematics wise, adding these to the respective y and x of the original point.
Make sure you anchor it at 0 degrees to align it.
Edit: I haven't tried this equation in costume context yet, only for a costume that was specifically a line, but it should work just as well. If the equation only works in quadrant one (top left section relative to the sprite at 0 degrees) then make sure that Snap!'s degree system goes from 0->90->180->-90.
if not convert it to that so that x and y can be negative
Edit: Sorry for the lack of explanation, I was trying to hurry to leave for church. I am glad your problem was solved :).
There is a project Username=dardoro&ProjectName=world2map to check the coordinate translation
Green rectangle is a mini-map, the stage is a "world".
The green dot is a point on mini-map following the mouse pointer.
The calculated "world" position is marked by a red dot.