Generate AprilTags in custom layouts for AprilTag 3.

How to use the package

First, you will need to generate the code associated with the layout of your marker :

ant
java -cp april.jar april.tag.TagFamilyGenerator <layout> <minimalHammingDistance>

The choices of layout are :

• standard_x, new-style april tag with one pixel of data on the outside
• classic_x, old-style april tag
• circle_x, for circular april tag
• custom_[...]. For more details about this last one, please check https://github.com/AprilRobotics/apriltag-generation/blob/master/src/april/tag/TagFamilyGenerator.java

With x the size of the tag (in pixels). The smaller is x, the faster the generation is.

You will have as output into the terminal a string, starting from "package april.tag;" and ending at the end of the terminal. This string is your new code that will be use for generating your markers. Save it into a .java file (ex : TagStandard20h9.java), into src/april/tag.

Then, execute :

ant

Next, you can use this command to generate the C code associated with the marker :

java -cp april.jar april.tag.TagToC april.tag.<name_of_new_java_file>

Or generate your new markers as .png :

java -cp april.jar april.tag.GenerateTags april.tag.<name_of_new_java_file> .

NB : If the format of the markers is very small (ex : by default, 9x9 pixels), you'll need to rescale them. To do so, you may use the following command (Unix) :

convert <small_marker>.png -scale <scale_chosen_in_percent>% <big_marker>.png

Example usage for generating the 21h7 circular tag family:

$ ant
$ java -cp april.jar april.tag.TagFamilyGenerator circle_9 7

Then to generate the c code and tag images after copying the output into the source folder:

$ ant
$ java -cp april.jar april.tag.TagToC april.tag.TagCircle21h7
$ java -cp april.jar april.tag.GenerateTags april.tag.TagCircle21h7 .