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[Q] Function of white blocks in framemarkers?

November 29, 2013 - 7:29am #5

Hi,

I am using the framemarker PNGs on a white background. So the black outline is visible as well as the black 'pixels'. I notice that the PNGs also contain white 'pixels' which only become visible when overlaid on a coloured background.

As I'm using a white background, the white 'pixels' are not visible to the camera. Yet my app seems to work.

So what is the function of the white pixels? Would tracking improve if I overlay on a colour and both the white and black pixels are visible? Or can I only address a subset of the 512 markers if I only rely on black pixels?

Any enlightenment greatly appreciated.

 

 

Tom

[Q] Function of white blocks in framemarkers?

November 29, 2013 - 7:38am #4

As you've noticed, the white blocks are redundant w/ the black blocks. This provides for more robust detection and tracking over a broader range of backgrounds. 

The SDK converts all images to grayscale for processing and so colors are not significant. It's the luminance contrast of the image that it used by the tracker. So the best way to analyze background colors for FrameMarkers is to convert them to grayscale and look for ones that are a medium gray between black and white - i.e. so both the white and black blocks stand out against the background. 

[Q] Function of white blocks in framemarkers?

November 29, 2013 - 7:56am #3

Many thanks for your reply, David. So in short, am I right to understand that framemarkers on a medium grey background will result in better tracking than on a pure white background?

 

 

Tom

[Q] Function of white blocks in framemarkers?

November 29, 2013 - 8:06am #2

They should, but it's worth testing, the difference may be marginal. You're likely to see improved detection times, but the tracking performance may be nearly equivalent.

[Q] Function of white blocks in framemarkers?

November 29, 2013 - 1:01pm #1

Many thanks, definitely worth trying.

 

 

Tom

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