IMAGE NOT SHOWING android apk

Question

Image showing the problem. I was trying to edit an apk file, in particular an image but when I open it from my phone what appears instead of the chosen image is a gray square Obviously I modified the pixels of the new photo like those of the old one. I changed all the dpi files related to that image but nothing, it doesn't work. Help. I tried to find other information around but it doesn't work, it's as if the app forbids the insertion of external images, because when I insert the original image again it works. it's very strange, I'm not an expert in fact it's my first app that I've tried to mod, if you need some kind of code just ask. Thank you