sf_filter.asv

% spatial frequency (SF) filtering by SF-bandpass filter

% the SF filter is unselective to orientation (doughnut-shaped in the SF
% domain).

% parameters for SF filtering
ctrSF = 1/(40*2); % center SF
s = ctrSF/0.5; % sigma of Gaussian function
ctrSF = 0;

show_log_amp = false; % flag to show log SF spectrum instead of SF spectrum
min_amp_to_show = 10 ^ -10; % small positive value to replace 0 for log SF spectrum

filtered_magnified = zeros(size(filtered));

img1 = filtered(1, 1, :);
img1 = reshape(img1, imgDim);

% calculate the number of points for FFT (power of 2)
FFT_pts = 2 .^ ceil(log2(size(img1)));

if 1
for i = 1:%size(filtered, 1)
    for index = 1:1
        img = filtered(5, index, :);
        img = reshape(img, imgDim);
%img(abs(img) > 0.2) = 0;
%img = blurDn(img, 1);
%img = imresize(img, imgDim);

        [img_spektrum fx fy mfx mfy] = Myff2(img, FFT_pts(1), FFT_pts(2));

        SF = sqrt(mfx .^ 2 + mfy .^ 2);

        % SF-bandpass and orientation-unselective filter
        filt = exp(-(SF - ctrSF) .^ 2 / (2 * s ^ 2));

        img_spektrum_filtered = filt .* img_spektrum; % SF filtering
        img_filtered = real(ifft2(ifftshift(img_spektrum_filtered))); % IFFT
        img_filtered = img_filtered(1: size(img, 1), 1: size(img, 2));

        filtered_magnified(i, index, :) = img_filtered(:);
    end
end
end

if 0
img = filtered(5, 1, :);
img = reshape(img, imgDim);
%imagesc(img1)
caxis([-0.3 0.3]);
img(abs(img) > 0.2) = 0;
img = blurDn(img, 1);
img = imresize(img, imgDim);
end
[img_spektrum fx fy mfx mfy] = Myff2(img, FFT_pts(1), FFT_pts(2));
%return;

figure(1);
clf reset;

colormap gray;

% luminance image
subplot(2, 2, 1);
imagesc(img);
colorbar;
axis square;
set(gca, 'TickDir', 'out');
title('original image');
xlabel('x');
ylabel('y');

img_spektrum = abs(img_spektrum);
if show_log_amp
    img_spektrum(find(img_spektrum < min_amp_to_show)) = min_amp_to_show; % avoid taking log 0 
    img_spektrum = log10(img_spektrum);
end

% spectral amplitude
subplot(2, 2, 2);
imagesc(fx, fy, img_spektrum);
axis xy;
axis square;
set(gca, 'TickDir', 'out');
title('amplitude spectrum');
xlabel('fx (cyc/pix)');
ylabel('fy (cyc/pix)');

% filter in the SF domain
subplot(2, 2, 3);
imagesc(fx, fy, filt);
axis xy;
axis square;
set(gca, 'TickDir', 'out');
title('filter in the SF domain');
xlabel('fx (cyc/pix)');
ylabel('fy (cyc/pix)');

% filtered image
subplot(2, 2, 4);
imagesc(img_filtered);
colorbar;
axis square;
set(gca, 'TickDir', 'out');
title('filtered image');
xlabel('x');
ylabel('y');
return

cx=65;cy=65;ix=128;iy=128;r=5;
[x,y]=meshgrid(-(cx-1):(ix-cx),-(cy-1):(iy-cy));
c_mask=((x.^2+y.^2)<=r^2);
imagesc(c_mask)