I've been working on processing of DNA gel electrophoresis images. Can anyone suggest me a method to determine the size of the dna bands after segmentation? Thanks in advance.

i used the following code to segment the image clear; close all; f = imread('Fig1022(a)(gel-image).tif'); h = fspecial('Sobel'); fd = double(f); g = sqrt(imfilter(fd, h, 'replicate').^2 + ... imfilter(fd, h', 'replicate').^2); %computing the gradient by Sobel operator directly subplot(231); imshow(f, []); title(' the original image');

 L = watershed(g);
 wr = L == 0;                               % get the watershed ridge lines;
 subplot(232); imshow(wr);           % note the servere oversegmentation
 title('oversegmentation result');    %oversegmentation resulting fom applying the watershed 
  % tranform directly to the gradient magnitude image g, which due in part
  % to the large number of regional minima.
  %rm = imregionalmin(f);             % compute the location of all regional minima.
  rm = imregionalmin(g)  % compute the location of all regional minima of gradient image
 subplot(233); imshow(rm);
 title(' regional minima of gradient magnitude image');

 % To eliminate these extraneous minima, IPT function imextendedmim can be used
 % this function uses the extended minima transform suggested by Soille [2003]
 im = imextendedmin(f, 2); % obtain the internal markers
 fim = f;
 fim(im) = 175;  % superimpose the extended minima locations as gray blobs 
 subplot(234); imshow(fim, []);
 title(' internal markers');

 % next external markers must be found
 Lim = watershed(bwdist(im));
 em = Lim == 0;
 subplot(235); imshow(em);
 title('external markers');

 % then, a so-called technique of minima imposition is used to modify the
 % original  gray-scale image.
% mp = imiposemin(f, mask);

 % modify the gradient image by imposing regional minima at the location of
 % both the internal and external markers
 g2 = imimposemin(g, im|em);
 subplot(236); imshow(g2, []);
 title(' modified gradient image');

 %at last, compute the watershed transform of the marker-modified gradient image
 L2 = watershed(g2);
 f2 = f;
 f2(L2 == 0) = 255;
 figure; imshow(f2, []);
 title('improved segmentation results');