Image drawing is distorted when app run on scaled display

Question

Hi, I have a small C# utility app to take a 750x500 photo and cut it into puzzle pieces. Works perfectly on 100% display (96 DPI). If the same app is run on a device which has a 150% display (to make images/text more visible on a small screen), the puzzle pieces are no longer correctly cut: images are cut-off on the edges.

 

I have turned off the high DPI aware in the XML. Does not help. Must be a problem with some other code that is scaling and drawing these images?

 

Any suggestions welcome.