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# How to detect peaks in laser strip

Asked by Lalit Patil on 19 Nov 2012

I = imread('1.jpg'); z = im2bw(I); skel = bwmorph(z,'skel',Inf); imshow(skel)

I want to detect middle of laser strip in image 1, called peak detection.. i tried thinning and morphological operations, but it exactly doesn't work and gives image 2.. I want single middle line.. So, which function or logic or code may be applied, please suggest me...

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Answer by Image Analyst on 19 Nov 2012
Edited by Image Analyst on 19 Nov 2012

I'd just scan down line by line, determining the center on a line-by-line basis. You could just threshold and determine the center that way, or, if it has a nice non-saturated profile, use something like a Savitzky-Golay filter (a sliding window polynomial fit, sgolay() is in the signal processing toolbox) to find the peak. The Signal Processing Toolbox also has a findpeaks() function. Then make groups where the column of the center doesn't move much from line to line. Then fit each group to a line with polyfit().

Lalit Patil on 20 Nov 2012

If i follow your first statement then i write a code that gives all centre points to me.. But, then how to create centre line image from it..!

And if i follow second statement then i got following image. http://www.fileconvoy.com/dfl.php?id=g1835684e61f18243171923475a58f31fdedd20 I think the space between the three different regions get filled, so this second can not be applied...

But still the problem is same.. How to create image from first solution.?

Lalit Patil on 20 Nov 2012

Ok... Now i understand the concept... In real i need only that middle points and saved it to text file, no need of image.. and i got it.. I have done same as per your first suggestion "scan down line by line" Thank you...

Answer by Harshit on 19 Nov 2012

It is not possible due to noise. Although if you just want a line use hough transform to get different lines and then select the biggest line.

## 1 Comment

Lalit Patil on 19 Nov 2012

If i do this, Image = imread('1.jpg'); bwImage = im2bw(Image); imshow(bwImage)

then the noise is removed, now i want to detect middle single straight line.. How can i do this..?