How to determine the period of a pattern contained in a grayscale image?

Hello,

I want to determine the period of a specific pattern in a grayscale image. The matrix representing the image is a 86x60000 matrix containing values between 0-255 (grayscale). I read about different approaches using functions like findpeaks, ischange and crosscorrelation to determine the period but I am not quite sure how I could use them in order to solve my problem. I am new to matlab and therefore I am not familiar with all functionalities matlab provides. Do you have any ideas how to tackle this problem?

Here is a picture that illustrates what I want to calculate.

Answer 1

[Image Analyst]

Not too hard. Just threshold then scan to find the top edge. Then invert and call findpeaks. Here's a start

grayImage = imread(fileName);
if ndims(grayImage) > 1
    grayImage = rb2gray(grayImage);
end
mask = grayImage > someThresholdValue;
[rows, columns] = size(grayImage);
topRows = rows * ones(1, columns);
for col = 1 : columns
    tr = find(mask(:, col), 1, 'first');
    if ~isempty(tr)
        topRows(col) = tr;
    end
end
% Invert
topRows = rows - topRows;
% Find peaks
[peakValues, columnsOfPeaks] = findpeaks(topRows, 'MinPeakDistance', columns/10);
peakValues = rows - peakValues;
% Plot on image.
hold on;
x = 1 : columns;
plot(x(columnsOfPeaks), peakValues, 'rv', 'MarkerSize', 15, 'LineWidth', 2);

Attach your actual image if you can't figure it out.

[Glypton]

Thank you for your response!

I am new to image processing. There is no image per se. Just a big matrix with values between 0-255 or 150-255 since there are no black pixels contained in the matrix. The actual dimension of the matrix is 86x6*10^5. I extracted the first 6*10^4 columns to show you what I want to achieve. This means that the above pattern is repeated 10 times with some noises. Now I try to calculate the period of that pattern. So, there is no image but a big matrix. Sorry for being unclear and thank you again for your response!

[Image Analyst]

It doesn't matter what you call it: image or matrix. Essentially they're the same. If you need any more help, ask. And attach the matrix in a .mat file with the paperclip icon.