[doc] Add insta360 air camera doc

[knorth55]

add insta360 air camera

cc. @708yamaguchi

[708yamaguchi]

Thank you.

Why do you think we need jsk_perception/launch/libuvc_camera.launch?
I think sample_insta360_air.launch is enough.

Other than that, I think this PR is fine.

[708yamaguchi]

We may need libuvc_camera to run_depend of package.xml.

[knorth55]

libuvc_camera launch is also used in #2545 , that is why i added it.
libuvc_camera is needed to run,
but it is just sample so i didn't add it.
i dont know how hard the release is, but i think we should not add a lot of run dependencies for sample programs

[708yamaguchi]

OK, thank you for your explanation.

[knorth55]

@k-okada Travis passed, can you please merge this PR?

[708yamaguchi]

FYI:
The mjpeg format of libuvc_camera is not available in indigo and fetch15 cannot use this launch file.
The following comment is helpful.
ros-drivers/libuvc_ros#37 (comment)

Instead, I was able to view the insta360 mjpeg images by using usb_cam.
http://wiki.ros.org/usb_cam

[708yamaguchi]

@knorth55 @YoheiKakiuchi how can I get panorama view image from 360 fisheye camera?

[knorth55]

@708yamaguchi what do you mean by panorama view image?
if you mean the rectified image, you need to calibrate the camera.

[708yamaguchi]

I mean panorama view image like below.
http://rraj.rsj-web.org/atcl/749

If calibration is needed, do you know a good method to calibrate the camera?

[knorth55]

I think it is better to calibrate the camera as normal camera, split into several images and recognize objects and human separately.

FYI:
paper: http://www.ee.oulu.fi/~jkannala/publications/tpami2006.pdf
fisheye camera model name: ros/common_msgs#109
fisheye calibration: ros-perception/image_pipeline#440
fisheye camera model: ros-perception/vision_opencv#358
fisheye image_proc: ros-perception/image_pipeline#441

[YoheiKakiuchi]

Is there a recognition technique that uses original fisheye image ?
Opencv calibration is not so easy with a checkerboard, which is usually done with a normal lens, because the distortion is so large.

The opencv calibration just transform from a fisheye model to a pinhole model.
So you'll need to use narrow angle of view, or more than two images.

I think the panorama view is using N images which are connected in a nice way,
but I can't find a paper or an implementation.

[knorth55]

Is there a recognition technique that uses original fisheye image ?
Opencv calibration is not so easy with a checkerboard, which is usually done with a normal lens, because the distortion is so large.

Which version of opencv have you done with?
From opencv3, fisheye camera model and calibration is introduce, so I think it is not so hard as it was (I hope).
image_pipeline camera calibration now supports fisheye calibration, so we can try it.
(however, we still don't have the image_proc for fisheye camera model)

https://stackoverflow.com/questions/50857278/raspicam-fisheye-calibration-with-opencv
https://docs.opencv.org/3.0.0/db/d58/group__calib3d__fisheye.html

I think the panorama view is using N images which are connected in a nice way,
but I can't find a paper or an implementation.

If you want to make panorama view with no calibration, we need to spin the camera in z-axis, capture images and concatenate them, in my understanding.
If there is any technique to make a panorama from no calibrated fisheye camera, I really want to know it.

[knorth55]

@708yamaguchi BTW, can you also add launch file for usb_cam and add args use_usb_cam in sample_insta360.launch?

[708yamaguchi]

@YoheiKakiuchi @knorth55
Thank you very much for your information.
I understand that I need to find good method by myself if I want to create panorama view or to do fisheye rectification on ROS...

@knorth55
Thank you for merging my PR to you.

[knorth55]

@k-okada Travis passed! Can you merge this PR?