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How to detect AprilGrid? #328
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The apriltag library needs a white border around the tag to do the edge detection properly. This border is interrupted by the black squares on the corner of the tags. |
The apriltag library only supports a black border width of 1. It looks like in your image the border width is 2, which is why it is not detected |
@wfxcqsc I tried your AprilGrid image with Alternatively, you can also try the "AprilTags C++ Library" from https://people.csail.mit.edu/kaess/apriltags/ (https://bitbucket.org/kaess/apriltags/src/master/) which generally supports tag families with multiple black border sizes: https://bitbucket.org/kaess/apriltags/src/3aea96d3239bb83870cb5e0a85f142a2b0589563/AprilTags/TagFamily.h#lines-64. |
Thanks for your reply!in fact, when I using opencv_demo to detect AprilGrid which have black squares on the corner of tags, I can not detect any detections. but I have detected AprilGrid successfully by using Kalibr,and I will also try the “AprilTags C++ Library”. |
hello,I am confused with the AprilGrid, when i detect the following picture(Apriltag board) using the opencv_demo, it can be successfully detected.
![apriltag7](https://private-user-images.githubusercontent.com/76416341/329563922-2098c267-1d9c-48eb-b27b-f7bec39700b4.jpg?jwt=eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.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.WPonXfn4qgNwhSGi1g1Dd2S4xQDJODPA_RkJIKOlJHE)
however,when detect the AprilGrid, it can not detect, i guess the reason is the the border width of Apriltag board is one ,while AprilGrid with border width the size of two
![apriltag3](https://private-user-images.githubusercontent.com/76416341/329563416-a9fedf08-7a4a-4eb4-b523-f3fd2e025f0d.jpg?jwt=eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.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.txXeozfCnqt8Y_cJSAfyWgQ7di3mUHxZ72Jl9-P64qM)
so,i want to figure out whether can set the borderbits, and how to detect AprilGrid?
Looking forward to your reply!
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