Autonomous seam detection on matlab

I'm trying to detect the seam on the following image

I wanna find pixels position of the detected line(red line in desire image) on the original image.

use the following code and finally removed noise from image reach this result

clc,clear,clf;
im = imread('Im.png.png');
imshow(im);title('Original image'); pause(0.5);
sim = edge(im, 'sobel');
imshow(sim);title('after Sobel'); pause(0.5);
mask = im > 5;
se = strel('square', 5);
mask_s = imerode(mask, se);
mask(mask_s) = false;
mask = imdilate(mask, se);
sim(mask) = false;
imshow(sim);title('after mask');pause(0.5);
sim= medfilt2(sim);
imshow(sim);title('after noise removal')

unfortunately there is nothing remain to find the seam perfectly.

any help would be appreciated.

Downlaod original image.