MATLAB Answers

Pixelsize of my GUI

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MrMedTech on 12 Apr 2016
Commented: Walter Roberson on 14 Apr 2016
hi together,
I'm doing a calculation with matlab wherefor I need the size of one Pixel.
I'm using a webcam, that works with 1024x576 pixel resolution.
My screen runs with 1920x1080.
So I created a gui and put a axes-system in there. I took pixels as untis and gave them 1024x567 width and height.
Than I changed units to centimeters to see how big it is so I can calculate the size of one pixel.
But the named size does not fit to the size I measured with my tape measure on de screen.
Does anyone of you have an idea? It's a difference round about 1 centimeter.
Thx Phil


Walter Roberson
Walter Roberson on 12 Apr 2016
Are you using an external display? External displays lie about their pixel density more often than not. Low resolution laptops lie about their pixel density a lot too.
MrMedTech on 14 Apr 2016
I'm working with a general Desktop. I downloaded a measure tool which shows me a ruler on my desktop on which a can read the pixel an cm value. But that doesn't fit to the result I get when I use a ruler manually. Maybe I should calculate the ratio between both results and define my pixelsize this way. Any other suggestion?
THX Phil
Walter Roberson
Walter Roberson on 14 Apr 2016
get(0,'ScreenPixelsPerInch') will probably be consistent with what it thinks the physical size is.
Yes, you need to measure and take ratios. And that will be OK for that one system with that one monitor with that one graphics card settings in that particular software release. Provided no-one twiddles the controls of the monitor.
If that sounds a bit pessimistic... Well when you have been around enough monitors you will find that there are Good Reasons why monitors cannot report accurately, but that it is also really common for monitors to not even try much to be correct.

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