optical image processing

8/8/2019 Optical Image Processing

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Coherent lowpass filtering

Filter yang meloloskan intensitas rendah

Semua koefisien matriks filter harus positif

Sumber : pola ruji (Spoke Pattern) Input filter : gambar lingkaran

Output : lowpass filter, radius spatial filter,and corresponding radius pada domain

frekuensi spasial



Gambar yang akan difilter

Spoke Pattern



Digunakan sebagai input filter filter spasial lingkaran

Spatial Filter



Intensitas warna putih (intensitas tinggi) berkurang

Gambar yang sudah terfilter



%@@@@@@@@@@@@@@@@@@@@@@@@@@@

%Input Spoke Pattern

s=256;

n=40; %Jumlah ruji/spokes

for x=1:s

xt=(2*(x-1)/(s-1))-1;for y=1:s

yt=(2*(y-1)/(s-1))-1;

r=xt^2+yt^2;

t=floor(atan2(yt,xt)/pi*n);

spo(x,y)=(r<=0.90)*(mod(t,2)>0.5);

end

end

%Input image

Input=spo;

%End of input image

%@@@@@@@@@@@@@@@@@@@@@@@@@@

Program Gambar Sumber

Matrix ukuran

x*y bernilai 0atau 1



%Fourier transform of the input image

F_Input=(1/256)^2*fft2(S_Input);

F_Input=fftshift(F_Input);

%**********************************

%circular opening at the fourier plane corresponds to lowpass filtering

%Low pass filter

pu=zeros(256);Ro=60; %M determimes the size of the low pass filter

for n=1:256

for m=1:256

if (n-127)^2+(m-127)^2<Ro^2

pu(n,m)=1;

end

end end

R=Ro/255; %R is radius of spatial filter in spatial domain

disp(R)

%End of pass filter

%**********************************

Menggunakan DFTuntuk merubah kedomain frekuensi

kemudian mengatur frekuensi 0 pada pusat

Program Pemfilter

Memberikan

warna putih untuk radius < 60



Pemfilter pada spatial &frequency domain%Display spatial filter

figure(3)

image(X,Y,256*pu)

colormap(gray(256))

title('Spatial Filter in Spatial Domain')xlabel('cm')

ylabel('cm')

axis square

%Spatial filter

kr0=R*2*pi/dx;



Pemfilter pada spatial &frequency domain%Flip the spatial filter

pu=fliplr(pu);

pu=flipud(pu);

S_pu=zeros(256);

S_pu=pu;%Display the filter in frequency domain

figure(4)

image(Kx,Ky,256*S_pu)

colormap(gray(256))

title('Spatial Filter in Frequency Domain')xlabel('rad/cm')

ylabel('rad/cm')

axis square

Mengubah urutan matirx



Program Filter & Output

%Filtering in frequency domain

F_Output=F_Input.*S_pu;

Output=ifft2(F_Output);

Output=(256^2)*Output;

%Output=fftshift(Output);

%Display the filtered output

figure(5)

image(X,Y,256*abs(Output)/max(max(abs(Output))))

colormap(gray(256))

title('Filtered Image')xlabel('cm')

ylabel('cm')

axis square

Bentuk dari konvolusi

yang kemudian diinfvers FFT spuaya

kembali dalam domainspatial



Coherent bandpass filter

Memiliki kelebihan untuk menentukanbatas tepi frekuensi yang diloloskan



Gambar pemfilter



Memiliki rentang nilai intensitas rendah hingga intensitas tinggi.

Gambar setelah difilter



Program Gambar Pemfilter

%**********************************

%Annular opening at the fourier plane corresponds to bandpass filtering

%Bandpass filter

pu=zeros(256);

%Outside radius=a/255 (unit length), inside radius=b/255

a=30;

b=20;for n=1:256

for m=1:256

if (n-127)^2+(m-127)^2<a^2

pu(n,m)=1;

end

end

end for n=1:256

for m=1:256

if (n-127)^2+(m-127)^2<b^2

pu(n,m)=0;

end

end

end










figure(5)


colormap(gray(256))

title('Filtered Image')xlabel('cm')

ylabel('cm')

axis square



Incoherent Spatial Filtering

Terdapat tambahan pada fungsi transfer berupa OTF (Optical Transfer Function)



Gambar Filter



Gambar Optical Transfer Function



Gambar setelah difilter



Program Gambar Pemfilter

pu=zeros(256);

%Outside radius=a/255 (unit length), inside radius=b/255

a=50;

b=10;

for n=1:256

for m=1:256

if (n-127)^2+(m-127)^2<a^2 pu(n,m)=1;

end

end

end

for n=1:256

for m=1:256

if (n-127)^2+(m-127)^2<b^2 pu(n,m)=0;

end

end

end



Program OTF

%Spatial filter

%kr0=R*2*pi/dx;

%Flip the spatial filter

pu=fliplr(pu);

pu=flipud(pu);

S_pu=zeros(256);

S_pu=pu;

%F_S_pu is the fourier transform of H(kx,ky)

F_S_pu=fft2(S_pu);

F_OTF=F_S_pu.*conj(F_S_pu);S_pu=fftshift(fft2(F_OTF));

S_pu=S_pu/(max(max(abs(S_pu))));

%S_pu is the OTF of the system










figure(5)


colormap(gray(256))

title('Incoherent Filtered Image by annular spatial filter')xlabel('cm')

ylabel('cm')

axis square

optical image processing

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