Taking slices from several images and stitching them together

Hi everyone, i have several images like the one which can be seen here :

In all images the location of the two bars are always in the same position on the y axis. They only change intensity.

I would like to take a pixel row at a certain height on the y axis of all images, stitch them together and display the resulting image.

So far i have the following in Matlab:

A =imread('image0000000351.pgm');
A = floor(A./16); % transform back to 12 bit
[n m] = size(A);
B=A-400; % remove background noise 
imagesc(B);

I'm a bit lost at this stage. How would i proceed to cut a slice on the y axis for several images and stich them together?

Answer 1

[Image Analyst]

Just extract the line from this image and add it into some accumulation line.

sumOfLines = zeros(numberOfImages, columns);
for k = 1 : numberOfImages
    % Read image.....
    baseFileName = sprintf('image....... whatever.....
    fullFileName = fullfile(folder, baseFileName);
    A =imread(fullFileName);
    A = floor(A./16); % transform back to 12 bit
    B = A - 400; % remove background noise 
    imshow(B);
    thisLine = B(desiredRow, :);
    sumOfLines = sumOfLines + double(thisLine);
    drawnow;
    pause(0.2); % Wait long enough to see it.
end
averageLine = sumOfLines / numberOfImages;
plot(sumOfLines, 'b-');
grid on;

You need to figure out the number of lines and the number of columns but there are ways to do that - either you know in advance or you check the size after you read in the very first image. And of course you might want to make it more robust by checking that the number of columns is the same for every image, and that the image actually exists before you try to read it in.

[Darellon]

Thank you for your answer. I've done the following:

sumOfLines = zeros(91, 1312); %(numberOfImages, columns)
for k = 300 : 390 
    % Read image.....
    baseFileName = sprintf('image0000000%3d.pgm',k);
    fullFileName = fullfile('C:\Users\Moz\Documents\MATLAB\hyperspec\images\', baseFileName); 
    A =imread(fullFileName);
    A = floor(A./16); 
    B = A - 400; 
    imshow(B);
    thisLine = B(595, :); 
    sumOfLines = sumOfLines + double(thisLine);
    drawnow;
    pause(0.2); % Wait long enough to see it.
end
averageLine = sumOfLines / 91; 
plot(sumOfLines, 'b-');
grid on;

and i get the following errors Error

 Error using  +  
Matrix dimensions must agree.

Error in doit4 (line 11)
    sumOfLines = sumOfLines + double(thisLine);

my A value is

1082x1312 uint16

[Image Analyst]

And what are the sizes of sumOfLines and thisLine? They need to be the same number of elements and both must be row vectors, not column vectors.

See http://blogs.mathworks.com/videos/2012/07/03/debugging-in-matlab/

[Moritz P.]

Thank you for your help.

[Image Analyst]

Sorry, actually sumOfLines should be a 1D array:

sumOfLines = zeros(columns);