Ask Your Question

Detecting LED array

asked 2014-07-17 07:13:42 -0500

R0b gravatar image

Hey guys,

im working on a project (Qt & C++) to detect an 10x11 LED array in an image. I need the (center)coordinates from each LED to measure the time. I tried several methods (HoughCircle, contour detection, blob detection) but non of them is robust enough to detect all 110 LEDs due to changes in illumination, reflections on the LEDs and noise in the image. Has anyone an idea how to deal with this?

My image roi looks like this:

image description

edit retag flag offensive close merge delete



Just switch to HSV space and threshold on the red color region. That will work perfectly in this case and illumination is less important in that space.

StevenPuttemans gravatar imageStevenPuttemans ( 2014-07-17 07:16:17 -0500 )edit

Thx Steven, but detecting only the red ones is not my problem. I need the coordinates from all 110 LEDs no matter if they're on or off.

R0b gravatar imageR0b ( 2014-07-17 07:25:41 -0500 )edit

Can't you fix the camera and mark the LED centers manually?

Witek gravatar imageWitek ( 2014-07-17 13:16:24 -0500 )edit

No, different cameras and focal length.

R0b gravatar imageR0b ( 2014-07-18 05:57:03 -0500 )edit

1 answer

Sort by ยป oldest newest most voted

answered 2014-07-17 08:35:00 -0500

Hi @Rob! Since your Background color is Different.

  1. Convert the Image into HSV Color Space.
  2. Filter the Background Image Color by using InRange()
  3. Apply Eroding & Dilate to the Binary Image.
  4. Find Contours & Filter them by Area and find the Bounding Box Center.
  5. Now You Know the Co-Ordinates of LED in Image ,the width and Height of each LED.
  6. Set ROI to this Region to decide whether it is ON or OFF by using HSV Values.

Share your work so that we can find were you struck.

edit flag offensive delete link more


Tried it but due to different illumination the delate/erode parameters have to change for some images, thats not very convenient for my task.

R0b gravatar imageR0b ( 2014-07-18 06:45:23 -0500 )edit

what have you tried? Update your code. Also have you noticed all these LED are properly Aligned? So have you considered to estimate these points?

Balaji R gravatar imageBalaji R ( 2014-07-19 08:16:43 -0500 )edit

Question Tools


Asked: 2014-07-17 07:13:42 -0500

Seen: 1,621 times

Last updated: Jul 17 '14