added proper comments and algorithm description for stripeeraser

1 files changed, 19 insertions, 6 deletions

diff --git a/stripeeraser.m b/stripeeraser.m
index b48a5b4..5d472fe 100644
--- a/stripeeraser.m
+++ b/stripeeraser.m
@@ -1,15 +1,28 @@
-function [immask,imfourier]=stripeeraser(img,radius,filter)
-immask=fftshift(fft2(img));
+function [img_cleaned,imfourier]=stripeeraser(img,radius,threshold_power)
+% Cleans an image from the stripes produced by interference fringes.
+% Such parallel fringes appears like a strong peak in the Fourier transformed image.
+% so it easy to clean them, especially if their spatial frequency is high.
+%
+% We will clean strong frequency components higher them max*10^(-threshold_power)
+% by suppressing them with exponential factor which is increases with distance
+% from the center i.e. zero spatial frequencies.
+
+immask=fftshift(fft2(img)); % move to Fourier space
 max1=max(immask(:));
 for x=1:640
     for y=1:480
         d=sqrt((x-320)^2+(y-240)^2);
-        if d>radius                                                        %Outside the central frequency.
-            if abs(immask(y,x))>max1*(10^(-filter));                       %The filter works like a neutral density filter. 
-                immask(y,x)=immask(y,x)*exp(-(d/radius)^2);                %Erase the frequency of the stripes.
+        if d>radius                                                        
+		% for high enough frequency components
+		%The filter works like a neutral density filter. 
+            if abs(immask(y,x))>max1*(10^(-threshold_power));                       
+		    % Suppress this frequency components which are mostly stripes
+		    % but leave untouched small sharp features of the beam 
+		    % since they are spectrally weak
+		    immask(y,x)=immask(y,x)*exp(-(d/radius)^2);
             end;
         end;
     end;
 end;
 imfourier=immask;
-immask=ifft2(ifftshift(immask));
+img_cleaned=ifft2(ifftshift(immask));