Woah... I'm genuinely concerned for you. What are you talking about? A screenshot should be a 1:1 pixel perfect match to the screen. It's a literal dump of the pixels on your monitor, that's what happens when you Print Screen on your keyboard. Even screenshots on Android are full size captures of the entire screen - even the pixels obscured by front camera cutouts. I know this because I've taken screenshots from my phone and put them in Paint.NET, the resolution of the image is identical to the resolution of the phone, all text is of identical fonts (whatever the HTML/CSS of the page says it should be).

Unless you're assuming AI post-processing is messing with images, but that's a much bigger and separate concern. Screenshots can be manipulated, and that means you can be manipulated.