Fingerprint Ridge Crossing

[koosdoos]

Hi guys ,

Does anyone know how to count the number of crossings between 2 minutiae in a fingerprint image ? For an example ive attached an image to make it a bit easier to understand .

Looking at the image , two minutiae are marked in red . OK . So connecting the 2 minutiae with a blue line i would like to count the number of ridges the blue line crosses . In this attached image the anwser would be 7 .

Does anyone know how this can be done , and in matlab ?


Thank you
Regards

Koosdoos

 

[leekk8]

Can you get all the coordinates where blue line going through? Let says your blue line is 1 pixel width, you can check the pixels beside the blue line. Check all the pixels along the blue line, when the pixel value from 0 to 1, then there is a ridge. Can you understand?

 

[smileysam]

very simple...
If u know the co-ordinates of the minutiae points find out the slope..Then use y=mx+c formula to get value of c at a minutiae point
now go from one minutaie point to other(preferably from the lowest i.e. (from (2,1) to (6,5) rather than (6,5) to (2,1));
the subsitute x from 2 to 6 & find out value of y round it off to an integer.
this will give u a line between 2 minutiae points & now count the trasitions from back to white & white to balck.. Num of ridges =num of transition/2;

 

[koosdoos]

Thanks SmileySam ,

Looking at the formula you gave me: 'y=mx+c' is 'm' the slope of the line ?

Thank you for your help .

Regards

koosdoos

 

[leekk8]

Yes, for y=mx+c, m is the slope. c is the intersection of the line and y axis.
Having computed this line to connect the 2 points, you can examine each pixel on that line. When the pixel change from white to black, there is 1 ridge.