How can i find out if two minutiae points in a fingerprint image are on the same ridge line?

Please i need help on how to know if two minutiae points on a fingerprint image are on the same ridge so as to be able to remove fake minutiae points from the fingerprint.

So I have done the extraction of minutiae points in the fingeprint image but how can i know if two of these minutiae points are on the same ridge line i.e. the same white line.

Thanks.

[darova]

What about bwlabel? You can separate each 'white' line and loop through all individually

Check if one has 2 points

[Fego Etese]

Thanks for your help on this, if i have two white points on the image how can i know with this method you've proposed that they are either on the same line or on different white lines? I mean if you could please just explain to me how the bwlabel can help me do this, I will be very grateful.

Thanks

Answer 1

[darova]

Simple example

I0 = imread('image.jpg');
I1 = ~im2bw(I0);
I2 = bwmorph(I1,'thin',inf);
I3 = bwareaopen(I2,30);         % remove lines bigger 30 pixels
[L,n] = bwlabel(I3);            % label each region

for i = 1:n
    Ic = L==i;                  % find region
    Ib = bwmorph(Ic,'branchpoints');    % branch/minutae points
    [y,x] = find(Ib);           % find coordinates minutae points
    II = cat(3,Ic,I3,I3*0);
    imshow(II,'initialmagnification','fit')
    hold on
    plot(x,y,'or')
    hold off
    pause(1)
end

I used attached image. So how do you want to remove points? And which one?

[Fego Etese]

Please don't be upset but i don't really understand what this code does and why it turns the thinned image green. What i want to do is to be able to confirm if any two minutiae points are on the same ridge, i have been able to extract the minutiae using crossing number algorithm and im trying to remove fake minutia by comparing each minutia with another one and checking if the distance bewteen them are below a value and also if the two minutia are on the same ridge. I can do the distance part but i don;t know how to confirm if they are on the same ridge.

[darova]

• What i want to do is to be able to confirm if any two minutiae points are on the same ridge

I think you have noticed that the code i posted highlights each ridge line separately

So you can easily check how many minutae points has each ridge line

just put this line inside for loop. It tells how many minutae points has current ridge line

length(x)

[Fego Etese]

Is the highligting of the ridges what makes the fingeprint turn green? and which of the function does this highlighting is it the bwlabel or the bwareaopen?

Then please i also noticed that it goes through all the ridges in the fingeprint image, but i dont want to go through all the ridges, i have a list of minutiae points that i want to compare each point to another one by one and also know if they are on the same ridge line during the comparision. Sorry if i'm causing a headache but I'm still a bit confused.

From what i uderstand so far, the code scans for minutie points in the for loop and can count how many minuitae points are on a ridge but i really just want to know if two minutiae points are on the same ridge not the number of minutiae points on a ridge.

Thanks

[darova]

Each color image consist of 3 color (Red,Green and Blue)

So image is 3D matrix I0 of size 204x293x3

Binary image (only white and black) is 2D matrix

So to highlight current minutae i just concantenated (merged) 3 matrices to create 3D matrix (color)

II = cat(3,Ic,I3,I3*0);                 % Ic - minutae, I3 - all lines, I3*0 - zeros
imshow(II,'initialmagnification','fit') % show together

[darova]

• i have a list of minutiae points

Can you show the data?

[Fego Etese]

This is what I mean, I have all the coordinates for the minutiae separately, but i am trying to compare each minutiae point with another one, like a ridge ending with another ridge ending, getting the distance and also finding out if the two endings are on the same ridge, the distance part i have done, i just need to know how to determine if the points are on the same ridge.

[Fego Etese]

The minutiae coordinates are stored in a 2 dimensional array

[darova]

Do you understand this line?

Ib = bwmorph(Ic,'branchpoints');    % branch/minutae points

[Fego Etese]

I think it finds the branchpoints in the image, that is the minutiae bifurcations. I do not understand it well, so i had to write my own code to find the endings and branchpoints. But please can you explain it to me and also the bwlabel, I have tried reading the docs on bwlabel but i don't understand what it does

[Fego Etese]

I think i understand the bwlabel better now, it groups connected regions together, please correct me if i am wrong, but i am thinking that to know if two minutiae are on the same ridge i can check their coordinates in the label matrix returned from bwlabel and see if the values are the same i.e. they are in the same region on the same ridge.

Do you think this could be the solution?

[darova]

• I think i understand the bwlabel better now, it groups connected regions together

You are correct

[Fego Etese]

Thank you so much for your time and patience. God bless!! ?

[Image Analyst]

Yes, if L(row1, col1) is the same as L(row2, col2) then they are on the same ridgeline, otherwise they are on different ridgelines.

[Fego Etese]

Thanks Image Analyst, I appreciate your help. I will do this.