Question

I’m working on app that needs user interaction to locate some points in image. because the image apear smaller in the app , I need to transform the points locations to a larger image. so I need the math to do so. to transform points to a larger image.

Answer 1

smaller image dimensions: Ws x Hs
bigger image dimensions: Wb x Hb

user taps smaller image at (Xs,Ys)

appropriate point on the bigger image (Xb,Yb) would be:

Xb = Xs * (Wb/Ws);
Yb = Ys * (Hb/Hs);

And for the other way around:

Xs = Xb / (Wb/Ws);
Ys = Yb / (Hb/Hs);