Please help me with image processing.

I need to find a tinny curved line in an image. I tried all of this but I cant find anything. Do I need a fancy function to make it work? I'll appreciate any of your comments. Thank you so much!!

 TRIAL1 

%constrast streching

x=input('enter the factor which contrast should be increased');
a=imread('Test 7 single bb.tif');
[m,n]=size(a);
for i=1;1:m
    for j =1:1:n
     b(i,j)= a(i,j)*x;
    end
end
subplot(1,2,1),subimage(a),title('original image')
subplot(1,2,2),subimage(b),title('contrast image')
%for some reason this one is not working.

TRIAL2

%Power law transformation

f = imread ('Test 7 single bb.tif');
f = im2double (f);
[m n]=size (f);c = 1;
%small number =brighter image
gama = input('gamavalue = ');
for i=1:m
 for j=1:n
  g(i,j)=c*(f(i,j)^gama);
 end
end;
imshow(f),figure, imshow(g);

TRIAL3

%log transformation 

f=imread('Test 7 single bb.tif');

   % you can change 0.02 for any number, small number gives you brigther images

g=im2uint8 (mat2gray (log (0.02+double (f))));

imshow(f), figure, imshow(g)

TRIAL4

%negative transformation

f=imread('Test 7 single bb.tif');

g = imcomplement(f);

imshow(f), figure, imshow(g)

[Image Analyst]

Please indicate which curved line you need to find.