what does marker size mean?

[hahazhky]

I set marker size to 100mm, but when I use ruler to measure its length, it is not equal to 100mm？
I have set the web page or pdf file proportion to 100%.
Thank you very much.

[okalachev]

Hi!

Marker's size is passed to CSS width and height of the containing svg element on the page.
I made a little research now, and figured out, that mm units are actually not physical millimetres, but just mapped directly to pixels (considering the density is 96 ppi). So this would work accurately only on some monitors.

I would consider this a bug, so some JS code should be added, to recalculate the element size correctly. So thank you for the report!

For now, as a workaround, you can open the .svg file in vector editing program, and print it from there, with the correct physical size.

[hahazhky]

@okalachev when I use OpenCV to generate Aruco marker, pixel size should be set. But when I use Aruco marker to do robot hand_eye calibration, physical size should be set. If I use OpenCV to generate marker, what should I do? Print it and then measure its physical size?

[okalachev]

You either measure its physical size yourself, or either edit you image in vector editing program to get a proper physical size.

[hahazhky]

I get it, thank you very much

[okalachev]

@hahazhky, can you please tell, which browser have you used to generate pdf to get incorrect measures? And have you printed out the pdf page?

[hahazhky]

Chrome or Firefox on Ubuntu16.04, I'm not very sure about that. I print it out and get about 97mm（I set to 100mm）

[jernejp21]

I have full HD monitor and using Firefox. If I use 133% zoom, marker size is correct on monitor.

I have downloaded markers and used Inkscape to rearrange them (printed out 24 at once, 35 mm size) and save as PDF. When I measured printed markers, the size was 33 mm. I didn't use printer connected to PC, so I don't know if print size was 100% or 95%.

I know that some printers shrink A4 paper by default when printing from Acrobat Reader and you have to be careful that it's 100% size.