Add lines on ImageView IOS (objective c)

I need some help to get this thing working..

Basically on button click, I have to add a line of fixed width with circle end points on the ImageView. User can add upto 5 lines. If I click on any circle (red dot) end point of line, it should allow to resize the line. Point can be dragged to any position on screen and line has to be straight. At the end, i should be able to calculate the length of each line. I just spent a lot of time on this and referring other similar answers. But so far, no luck.. Any reference code or links is greatly appreciated. Thanks!