[ros-users] Nodelet version of image_view

[Nicholas Butko]

Yes, but it didn't help, and I don't think it should matter (Isn't it called implicitly by namedWindow() which is called implicitly by imshow()? If not, it should be...) 

Anyway, in playing around with it, I had to call waitKey() from a custom nodelet manager in order to get any output. Unfortunately, this led to frequent crashes, in what looked like OSX graphics APIs. 

In the end, I settled on something where each node processed images, and prepares a graphical output as a published image, but doesn't display it. Then, using a separate image_view process, the output can optionally be displayed. This has the added benefit of using little overhead if you don't need the visualization, and so far it seems quite stable.

Again, this is my experience on OSX, so I don't know how it will generalize.

--Nick 


On Dec 7, 2010, at 1:13 AM, Patrick Mihelich wrote:

> Hi Nick,
> 
> In your nodelet, do you call cvStartWindowThread()? This is what allows image_view to update without explicitly calling cvWaitKey.
> 
> Cheers,
> Patrick
> 
> On Sun, Dec 5, 2010 at 5:22 PM, Nicholas Butko <nbutko at ucsd.edu> wrote:
> I was trying what is essentially this (nodelet image_view) today. I am having a problem, and I don't know if it's unique problem to OSX, or not. If it's unique to OSX, I'll try to fix it in OpenCV, but if not, it's probably better to fix it in nodelet.
> 
> The problem is that cvWaitKey never gets called from the main thread, and so the window content never updates. I have a perpetually white window. Calling cvWaitKey from the nodelet thread is not sufficient.
> 
> If you guys want to try this from Ubuntu, I'm happy to send source.
> 
> --Nick
> 
> 
> On Dec 5, 2010, at 2:24 PM, Radu Bogdan Rusu wrote:
> 
> > Bill, if you want to do that, I can do the point cloud part (pcd_viewer). Save some cycles, split some work. :)
> >
> >
> > On 12/05/2010 02:23 PM, Bill Morris wrote:
> >> On Sun, 2010-12-05 at 14:15 -0800, Radu Bogdan Rusu wrote:
> >> ...
> >>> Speaking of GUIs, it would be really nice to get image_view/rviz/pcd_viewer to have a nodelet component for displaying
> >>> data fast(er). Do you see any drawbacks of nodelets w. GUIs? If not, I might try to do the image_view/pcd_viewer part
> >>> next week as an exercise.
> >>
> >> I would really like to see a nodelet version of image_view if only to
> >> ensure proper operation of a nodelet camera driver.
> >
> >
> > Cheers,
> > Radu.
> > --
> > http://pointclouds.org
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