init

README.md

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+Periodic noise removing filter
+==========================
+
+Goal
+----
+
+In this tutorial you will learn:
+
+-   how to remove periodic noise in the Fourier domain
+
+Theory
+------
+
+Removes periodic noise, background and interferences in the Fourier domain. Useful for latent fingerprints, capture artifacts and electromagnetic interferences in videos
+
+
+Result
+------

src matlab/main6_papa_11.m

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+% 2016-01-04 
+% ðåàëèçîâàí àëãîðèòì óäàëåíèÿ òðàôàðåòíîé ñåòêè (ðàñòðà) ïðè ãàçåòíîé ïå÷àòè
+% background cell removing algorithm
+% 2018-08-16
+% ###added user interactivness
+
+close all,clc,clear all;
+
+imgA = imread('papa_1.bmp');
+imgA = rgb2gray(imgA); %color->gray
+figure; imshow(imgA);
+title('Original image');
+
+% user input:
+% %h = imrect();
+% pos = getPosition(h);
+
+img_fft = fft2(imgA);   %spectrum 
+img_fft(1,1) = 0;   %removing of constant component
+imgB = img_fft.*conj(img_fft);  %Power spectrum density
+imgC = fftshift(255*(imgB -min(min(imgB))) /(max(max(imgB)) - min(min(imgB))));
+figure; imshow(imgC);
+title('Power spectrum density');
+imwrite(imgC,'output\Power_spectrum_density.bmp');
+
+[h w] = size(imgC);
+imgD = ones([h w]);
+
+%Array of noise. Enough first eight components
+x1 = [1620 1618 1211 1212 1416 1822 1414 1007 1409 1620 1726 1420 1212 1105 1622 1824 2028 2026 1821 1618 1208 1007 805  806 1010 1215];
+y1 = [ 912 1222 1221  911 757  1068 1377 1066 890  1009 1068 1242 1123 1064 602  757  914  1225 1378 1532 1532 1375 1220 907 754  602];
+
+n = 25; %size of removing spot. 30 - optimum
+for k = 1:size(x1') % k - index of noise component
+    for i =-n:n
+         for j =-n:n
+                imgD(y1(k)+i,x1(k)+j) = 0; %imgD(row, colomn), this is why imgD(y,x) rather than (x,y)
+         end;
+     end;
+end;
+figure; imshow((imgC+imgD)/2);
+title('Power spectrum density + mask');
+
+imgE = ifft2(fftshift(imgD).*img_fft); %filtering
+imgE = real(imgE);  %it needs to get real part because imgE is complex value
+imgF = 255*(imgE - min(min(imgE))) /(max(max(imgE)) - min(min(imgE)));
+imgFF = uint8(imgF);    %in order to convert double to uint8
+figure; imshow(imgFF);
+title('Final image');
+% imtool(imgA,[70 217]);
+% imtool(imgFF,[46 178]);clo
+
+imgAA = imadjust(imgA,[70 217]/255);
+figure; imshow(imgAA);
+imwrite(imgAA,'output\Contrasted_original_image.bmp');
+%figure; imshow(imgA,[70 217]);
+title('Contrasted original image');
+
+imgFFF = imadjust(imgFF,[58 170]/255);
+figure; imshow(imgFFF);
+imwrite(imgFFF,'output\Contrasted_Final_image.bmp');
+%figure; imshow(imgFF,[58 170]);
+title('Contrasted Final image');
+
+figure, imshowpair(imgAA, imgFFF,'montage');
+figure, imshowpair(imgA, imgFF,'montage');