Length tool - How the image coordinates remain consistent even if the image is zoomed or if the viewport size differs

When I try to draw a line using the length tool, I want to know how the points are marked and how it remains consistent even if the viewport size changes. Please let me know where can i find this code in the OHIF folder structure.

it is in cornerstone3D , since we use worldCoordinate system, and not canvas, so no matter how much you zoom or pan, it is the same place

read more about world coordinate system here Coordinate systems — 3D Slicer documentation