I want to take screenshots that come out at 2880×1800 and show the exact color displayed on each pixel of my 15.4" rMBP, no matter what scaled resolution I am using. How can I do this? In particular, if I set my screen to 1680×1050, I want my screenshots to be 2880×1800 not 3160×2100. And if I set my screen to 1920×1200, I want my screenshots to be 2880×1800 not 3840×2400. You know, a snapshot of the screen.