How to render a scale (like a Ruler!) into a picture

Hello folks, a new day - a new problem.
Okay in my WebApplication i have a webform showing some pictures.
The pictures - or better - the picturepath i get from a database.
With this paths i am loding the pictures into my webform.

Now i want to render a scale into these pictures. For example lets say 1px = 1cm.
It should look something like in this sample picture:
 


Is it possible to realize somethin like that and how?!
I tryied to google something but i could not find anything!


Thanks in Advance! 


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