device pixel denisty and screen resolution

I'm trying to print 512x512 image to screen on center of my image. The image doesnt show when it's left as the original resolution which is 512x512. But when i scale my image by 200 factor its desplayed to the screen. The thing is i want to detect when the user clicks on my image using the on touch event. So i check if he pressed on my image by checking if the event.getX and event.getY are inside the texture boundries with its original height and width 512x512. This seems not to be working when i keep the scale value as 200 as this is not the actual size. And not even working when i leave it with its original size. So i want to know if there is a relation between the screen resolution and the pexil denisty of the device and also the captured video by vuforia. I'm using LG G2 with 1080x1920 ~414ppi and 13 MP camera. Thanks.