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I was trying to use DigitalColor Meter to find the color of a pixel on my retina MacBook Pro, but I found that it was impossible to get the color that I wanted because the smallest that I could move the mouse by was two pixels (in either direction). If you zoom in using the control-scroll trick and disable pixel antialiasing (in the Accessibility preferences), you'll also see that this is the case.

Is it possible to move the mouse by just one pixel on a retina display? It seems like the ability to do so would make the mouse movement smoother. I guess to solve my color problem, I could just take a screenshot and zoom in on that, but it's a lot of extra work.

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By the way, I've also noticed (by putting it really close to my eye) that scrolling on my retina iPad and iPhone moves by two pixels at a time. So maybe Apple really hasn't updated all their stuff to retina capacity as much as you would think. –  asmeurer Sep 14 '12 at 18:47
    
Oh, and I'm on Mountain Lion (but I vaguely remember that I first tried this before upgrading). –  asmeurer Sep 14 '12 at 18:49
    
Making scrolling and other tiny things move by 1 pixel on Retina displays is really resource intensive, and most people won’t notice any change. No one scrolls pixel by pixel. –  duci9y Sep 15 '12 at 5:59
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up vote 6 down vote accepted

No - the mouse is aligned on the "fake" size of the screen and not the true screen pixel grid in most cases.

The concept of a physical pixel and a display pixel is a distinct one on retina displays since the hardware reports movements on a resolution-independant scale.

Furthermore, there appear to be some subtle bugs in the code side of things so even if the developer wanted to determine the next pixel's color it appears the routine that reports mouse position doesn't count physical pixels on this model screen.

There is a nice, very technical article by one of the programmers for Xscope - Retina for Masochists/ that explains a bit how the resolution that the software is told to draw gets translated into the actual on screen pixels which is fixed.

As an aside - the Xscope program is free to try and puts the digital color meter to shame on many aspects of determining color and much, much more.

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Ah. So this is probably related to the way that it scales up or down a virtual display that I've heard about. –  asmeurer Sep 14 '12 at 20:56
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Thanks. I definitely don't need a $30 program for something I use maybe once a year, but the trial appears to work. For reference, to move by one pixel, you have to use the arrow keys on your keyboard. –  asmeurer Sep 14 '12 at 21:01
    
So are things more or less the same on the iPad and iPhone (see my first comment on the question)? –  asmeurer Sep 14 '12 at 22:17
    
Best to simply ask that question on it's own. You are the first to report it - so I haven't noticed it or seen it referenced anywhere before. –  bmike Sep 15 '12 at 17:54
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