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Image targets where color is inverted

December 14, 2018 - 4:35am #1

I am using a good quality black-and-white image target that tracks very well. However, an inverted version of the image (black and white parts reversed) will not track.

The attached images show the features of both images are the same. Should I add both targets to my application if I want to track positive and negative versions of the same target?

Image targets where color is inverted

December 18, 2018 - 4:40pm #2

Hello,

Yes, it should not work. Inverted image means changing descriptors, so no match is expected. I've found an explanation for how this works in SIFT, but in principle it's the same issue for Vuforia: https://stackoverflow.com/a/15044609

Some things to check:

  • Always print the image that was uploaded to the portal to the exact same aspect ratio. Any stretching or altering of the image will cause it not to be detected. Some printers default to "stretch to fit", which can change the aspect ratio.
  • Check the size values you are using when uploading Targets to the Vuforia Target Manager. Note there is specific language used in the dialogue box that says Vuforia uses meters as the default unit scale. Incorrect target sizes could affect either our detection/tracking algorithm, or the augmentation in that it so large that it cannot be viewed because it extends beyond the clipping plane.
  • Review ADB logs to see if Vuforia detects and tracks the target. If the target is being tracked but the augmentation cannot be seen, this could indicate an issue with the clipping plane.

Thanks,

Vuforia Engine Support

 

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