XnView Software

I would be nice to have an option to specify the screen PPI (Pixels Per Inch).

Currently it seems that it is automatically calculated using the system PPI scaling, in my case it is 150% (standard 96 PPI), so 144 PPI. My screen has 163.7 PPI actually, that means that when I use "real size" to view the actual size of an image (using the printing DPI settings) it is scaled incorrectly (about 12% smaller than the actual real size).

I know I could set my system wide DPI scalling to 170% and it would solve the issue but they are actually different things. One is the scalling of the UI elements to the right size you want them to be and the other is the real physical PPI for real representation of sizes in screen. I think it should be an option to set the actual screen PPI you want the application to use, and it shouldn't be hard to implement.

Thanks

you can set environment variable like QT_SCALE_FACTOR
Please check here

Thanks for your answer but that is not exactly the same.

If I do that it will scale all UI elements of all QT based applications. You could even do that for a an executable only.

But that is not the issue, the issue is that you should be able to have the UI element at the scale you want and also be able to display the real size of the image correctly. And the only way to do that is to have a separate setting for "real world" screen PPI.