[相機標定] 用Kalibr標定diy的雙目相機

由於diy的雙目相機沒有做時間上的硬件同步，想着看看標定一下內外參能不能湊合用。首先試了一下采用ros自帶的camera_calibration，感覺還行，在--approxiamte_sync=0.1的情況下能夠正常標定。於是想着試一下kalibr...

1. 參照之前博客標定d435i時候的操作，錄製數據集

$ rosrun topic_tools throttle messages /camera/stereo/left/image_rect 4.0 /left

這裏降頻到4Hz錄製圖像數據集，左右目都錄製。這裏錄製的是通過ros的stereo_image_proc發佈出來的rect_image話題。

2. 運行kalibr，這裏也不贅述了，參考我之前標定d435i時候的博客，進入到kalibr_ws工作空間下：

$ kalibr_calibrate_cameras --target /home/nan/dev/kalibr_ws/src/kalibr/data/checkerboard.yaml --bag /home/nan/dataset/labdata/diycams.bag --models pinhole-equi pinhole-equi --topics /left /right --show-extraction

 然後報錯了：

1569208515.99     -     88
1569208516.23     88     -
1569208516.27     -     88
1569208516.5     88     -
1569208516.53     -     88
1569208516.77     88     -
1569208516.8     -     88
1569208517.04     88     -
Cameras are not connected through mutual observations, please check the dataset. Maybe adjust the approx. sync. tolerance.
Traceback (most recent call last):
  File "/home/nan/dev/kalibr_ws/devel/bin/kalibr_calibrate_cameras", line 15, in <module>
    exec(compile(fh.read(), python_script, 'exec'), context)
  File "/home/nan/dev/kalibr_ws/src/kalibr/aslam_offline_calibration/kalibr/python/kalibr_calibrate_cameras", line 444, in <module>
    main()
  File "/home/nan/dev/kalibr_ws/src/kalibr/aslam_offline_calibration/kalibr/python/kalibr_calibrate_cameras", line 201, in main
    graph.plotGraph()
  File "/home/nan/dev/kalibr_ws/src/kalibr/aslam_offline_calibration/kalibr/python/kalibr_camera_calibration/MulticamGraph.py", line 308, in plotGraph
    edge_label=self.G.es["weight"],
KeyError: 'Attribute does not exist'

3. 接下來解決這個報錯的問題

 參考鏈接：https://github.com/shanmo/Kalibr-camera-calibration/tree/master/stereo%20camera%20calibration/preliminary%20test

於是：

$ kalibr_calibrate_cameras --target /home/nan/dev/kalibr_ws/src/kalibr/data/checkerboard.yaml --bag /home/nan/dataset/labdata/diycams.bag --models pinhole-equi pinhole-equi --topics /left /right --show-extraction --approx-sync 0.04 

就正常出結果了