how to find peaks in jpeg image

hi i am new in matlab, and i want to extract peaks from a spectrum peg image and store the peak in vector

this is a spectrum image jpeg file ,so how i can extract peaks from it

please help me .

Answer 1

[Shoaibur Rahman]

You can try with Mablab's findpeaks function, or see the attached code in file exchange:

http://www.mathworks.com/matlabcentral/fileexchange/48818-peak-detection-of-a-function

[Image Analyst]

Won't work, at least not right away. He said he does not have the data but has an image that is a scan of a printout. First, from that image, he needs to get the 1-D signal data, then he can use findpeaks().

Answer 2

[Image Analyst]

Try this:

http://www.mathworks.com/matlabcentral/fileexchange/36904-matlab-script-for-digitizing-a-published-graph

But you'll have to decide how many elements you want the signal divided up into, say 500 or 1000 elements. And once you do that you can't get any wavenumbers because all we know is that the first element is around 2180. We have no idea what the last element in the array would have for a wavenumber because it's not shown on the plot.

[Image Analyst]

guitoune's "Answer" moved here:

Thank you for your comment

Yes,this resolve the problem, but, i want MATLAB code that get peaks position without intervention of user, so the analysIS of peak doing automatically, because we want to get to the correct value of the point without mistake.

[Image Analyst]

guitoune, do you have actual numerical data, or all you have is a printed image of a graph?

[guitoune mohieddine]

I have a printed image jpeg like this , so code matlab get the peaks and valleys automatically, i thik you enderstand me , please help me .

image

[Image Analyst]

Do we need to assume that the axes can be tilted, or can we assume that they are aligned with the image rows and columns? What about the color of the plotted line? Black, blue, or any possible color, except pure white?