Save image from control of another window with button click.

Question

 

I have a winform app with few controls that loads an image and a datagrid to enter data. Issue: I want to save that image from my winform app when I click a button.

So far Im able to find the source window handle in C# code but do not know how to find that control and save the image...

I know I have to use winapi methods but do not know which ones...

Kindly provide some input or a sample code. I have attached the sample screenshot!!

Thank you...