For simple cases, where a manual method is enough, I do the following:

![image= ;][1]

Then, with the help of get coordinates (from the context menu):

    imageCut = ImageTrim[image, {{96, 222}, {421, 417}}]

Followed by:

    range = {{400, 900}, {2.1, 2.7}};
    Graphics[Inset[imageCut, Scaled[{0, 0}], {0, 0}, Scaled[{1, 1}]], 
     PlotRange -> range, AspectRatio -> ImageAspectRatio[imageCut], 
     ImageSize -> 400, Frame -> True, Axes -> False, 
     PlotRangePadding -> 0]

![enter image description here][2]

And then you can easily use the Get Coordinates

I know this I not perfect, neither complete. The following post talks a little more on the subject [Link][3].



  [1]: https://i.sstatic.net/uUXhL.gif
  [2]: https://i.sstatic.net/OaRmW.gif
  [3]: https://mathematica.stackexchange.com/questions/1524/recovering-data-points-from-an-image#comment3892_1524