moms-apriltag 2023.1.15

Generate apriltags, calibration targets, and camera (mono/stereo) calibration

Apriltag Camera Calibration Board Generator

Why? There didn't really seem to be an easy way to do this IMHO.

This library is able to produce both generation 2 and 3 apriltags all via python ( no C/C++ library compiling and linking).

However, you will need another library (like cv2.aruco) to decode the tags ... see below for more info.

Install

pip install moms_apriltag

Examples / Usage

See the jupyter notebooks in docs/jupyter folder for how to use this.

This package create a simple numpy image that can then be saved to a PNG or JPEG image and printed. For circular or custom tags, there is a toRGBA() function to save the tag to a png using any image library that can accept numpy array images.

Supported families are shown in the table below in the image and table:

Family	Generation	Hamming	Size	Data Bits	Unique Tags
tag16h5	2	5	4x4	16	30
tag25h9	2	9	5x5	25	35
tag36h10	2	10	5x5	36	2,320
tag36h11	2	11	5x5	36	587
tagCircle21h7	3	7	9x9	36	38
tagCircle49h12	3	12	11x11	49	65,535
tagCustom48h12	3	12	10x10	48	42,211
tagStandard41h12	3	12	9x9	41	2,115
tagStandard52h13	3	13	10x10	52	48,714

ref

#!/usr/bin/env python3
from moms_apriltag import ApriltagBoard
import imageio

board = ApriltagBoard.create(4,6,"tag25h9", 0.02)
tgt = board.board

filename = "apriltag_target.png"
imageio.imwrite(filename, tgt)

# for AprilTag v2
from moms_apriltag import TagGenerator2
from matplotlib import pyplot as plt

tg = TagGenerator2("tag16h5")
tag = tg.generate(4)

plt.imshow(tag, cmap="gray)

# for AprilTag v3
from moms_apriltag import TagGenerator3
from matplotlib import pyplot as plt

tg = TagGenerator3("tagStandard41h12")
tag = tg.generate(137)

plt.imshow(tag, cmap="gray)

Apriltags using opencv-contrib-python for Camera Calibration Target Detection

This library uses the builtin cv2.aruco module that can detect:

• DICT_APRILTAG_16H5
• DICT_APRILTAG_25h9
• DICT_APRILTAG_36h10
• DICT_APRILTAG_36h11

Decoders

cv2.aruco for calibration is built in, but it can decode generation 2 tags only.

• pupil labs (tested): https://github.com/pupil-labs/apriltags can decode generation 2 and 3 tags
• WillB97 (untested): https://github.com/WillB97/pyapriltags can decode generation 2 and 3 tags

Todo

• change the way the board is created, do a fixed scale size and add a margin with text saying the orientation, family, size, and maybe in the small squares next to the tags, put the number of the tag (number is for the lower left apriltag). I think this would help debugging and understanding what is going on
• insert stereo calibration code using pupil labs?
• move the opencv_camera calibration code with apriltags here
• refactor board code
• enable apriltag v3 markers in board

MIT License

Copyright (c) 2020 Kevin J. Walchko

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.