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Image Comparison - Detecting region of interest

December 22, 2013 - 9:45pm #1

Hi All,



I am using vuforia library for image detection and showing overlay on it, this works on the feature point concept. But say if i have one image in which it has two LED glowing and another similar image in which it has only one LED glowing out of two, then when i try this image detection with vuforia's sample code imageTarget, it detects both the image as same/similar. Basically it is not differentiating between this two images color combination ON and OFF LED colors. 

Anyone having idea on how can i differentiate between this two images on the basis of color combination or image comparison with vuforia ?


Thanks and Regards,

Vipul Parmar.

Image Comparison - Detecting region of interest

March 5, 2017 - 8:06pm #5

Hi Vipul,

May I know were you successful in achieving your requirement ? Please share some details.

Even I am trying the similar thing as posted by you.


Image Comparison - Detecting region of interest

December 23, 2013 - 6:47am #4

Firstly the Pose Matrix will give you the position of the Target - see the previous link.

Next you will need to use the dimensions of the Target to give you the extent (all 4 corners) of the Target in 3D space

  • Use the Target dimensions to give you the width and height
  • This should give you coordinates of each of the 4 corners in 3D space
  • From this you should be able to work out the coordinates of the Point - LED you wish to test

Take the LED 3D point you wish to test and transform this back into 2D space - to hopefully give you the coordinates in screen space, as indicated by the Dev Guide here:



From these coordinates you need to access the Screen buffer to access the pixels, and hopefully the region that contains the LED area that you wish to test.

As you can see, this is non-trivial, and it may take you some time

I do not know whether what you are trying to do will work, so you might wish to break it down into component parts and do a test, perhaps on your detection algorithm first i.e. without the code above.







Image Comparison - Detecting region of interest

December 23, 2013 - 3:16am #3

Thanks for your input Nalin, But i didn't get you. Can you please elaborate a bit more. 

Image Comparison - Detecting region of interest

December 23, 2013 - 2:12am #2

The coordinates of the target are implied in the Pose Matrix when a target is identified:



The units that the scene uses are defined in the online Target Manager when you uploaded your target, and you may be able to use this information to determine the relative position of the LEDs, and subsequently grab the image and test for intensity.




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