Weickert's coherence-enhancing filter

It is effective in enhancing fingerprint images or scanned images.

The process removes noise and closes small gaps in the ridges while leaving the locations of minutiae points unchanged.

B = COHERENCEFILTER(A,T) applies the coherence-enhancing filter to a grayscale or color image A with diffusion time T. Larger T implies stronger enhancement.
 
COHERENCEFILTER(...,'PARAM1',VALUE1,'PARAM2',VALUE2,...) can be used to specify additional method parameters. 

Requirements:

· MATLAB 7.5 or higher