Color filter using the color picker...tips?
17 year
I have this nice ring of glue that I would like to inspect for foreign material like the black speck at 3 O'clock on the ring. Then I would like to know the width of the ring, making sure the start stop point (the lump at 11 O'clock on the ring) isn't too thin or to thick at that point compared to the other points on the ring.

I thought I would start off by isolating the ring with the color filter.  I would pick the various colors in the ring using the color picker.  Trouble is, I can't seem to get the color picker to update on anything. Is this feature working for anyone else?

I also tried the color threshold tool and it only seems to update if the image window is clicked and then the color threshold panel is clicked.  Could this be changed to update whenever one of the sliders is moved?

Once this is figured out, next steps would probably be to look for the black speck on the ring with the blob filter.  I would think that the "blob inner" or "blob within" tool would one way to start.

After that we can move onto width measurent.  Another post showed finding the edges, cropping the image horizontally, and measuring the distance between blobs. This could also be done for two measurements vertically.  What to do about the 11 O'clock position?

So, backing up, let's try and isolate the ring first.

Thank you!


P.S.  I played with the save avi and save images features and was most impressed with the framerate.  I was recording to disk at around 20 frames per second @ 640x480 in color. This is very impressive considering the program is being fed by a webcam.  Well done!
Anonymous 17 year
Hi, I've not had much luck with the colour picker either, so I've had a go using the RGB filter -attached.
Almost there...
Pete  [6 posts]
17 year
Thanks for the try Chas.  That does work well for the black speck.
I would like to get the color picker working though in order to isolate the entire ring so that the width can be checked at various points, the lump at 11 O'clock being one of them.  Because the lump color is a bit off from the rest of the ring, it gets dropped out with the RGB filter.

If the color filter color picker works as described, I would think I could sample various areas of the ring and add all its different shades and hues
to the filter. That way the entire ring should stand out.

Thanks again,

Ring of Glue
17 year
Hi Pete,

That was a tricky one. We did fix the color picker in the color filter module but that (as expected) does not help. The issue is that the color of the ring is too close to the surrounding pink area to reliably threshold.

So, instead of that we first apply the Canny edge detector

which outlines the ring nicely but has some disconnected points in the circle (which is normal for canny). So we add in the "Connect Points" module which will connect those end points. Further we dilate the edges to ensure that they separate the objects in the next steps. With these two modules we get

which we then use the math module to combine these lines with the original image to get

which separates the objects. Now we can use the "flood fill" module to average the color in each object. This makes the object a lot flatter and easier to pick out the object using just color.

At this step you could also use the other blob filters to remove the other objects ... but we'll stick with color for now. Using the color filter module (with the now working picker) we select the color and get

which is basically what we want ... to then bring back in the original colors we can use the math module again to finally get

and if you want to use the technique in the other post for measuring the distance you can simply rotate the image by about -60 degrees to align the lump on the horizontal axis. See Rotate module.

Note that you will need to download RR v1.7.2.21 to run the robo-file below to see those changes.

Very nice... Works well!
Pete  [6 posts]
17 year
That works well!  

Lighting seems to be very important for consistant results, which is expected. Changes in lighting result in changes in color levels.  

Do you think that there would be any value in being able to change the  threshold settings of the Canny edge detector with variables?  I was thinking that an area of the image could be looked at, the Color Statistics evaluated, and the Canny edge detector threshold settings modified accordingly.  This might help with lighting variations.

I really like the flood fill module now.  I was trying to use it earlier, but didn't get very far with it.  Your method shows the power available if the image is segmented with an edge tool.

Thank you for fixing the color picker.  


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