Image Compression using DCT and FFT techniques



Here we take a file and then compress the file applying DCT and FFT on the image. The compression is done
1. 70%
2. 50%
3. 30%
4. 10%.

The Code is like this :

clear all;
p=imread('kaka.jpg');
a=imresize(p,[100,100]);


%DCT
Z(:,:,1)=dct2(a(:,:,1));
Z(:,:,2)=dct2(a(:,:,2));
Z(:,:,3)=dct2(a(:,:,3));

for i=1:100
    for j=1:100
        if((i+j)>60)
            Z(i,j,1)=0;
            Z(i,j,2)=0;
            Z(i,j,3)=0;
        end
    end
end
K(:,:,1)=idct2(Z(:,:,1));
K(:,:,2)=idct2(Z(:,:,2));
K(:,:,3)=idct2(Z(:,:,3));
subplot(2,4,1);
%imshow(Z);
imshow(uint8(K));
title('70% compression');

Z(:,:,1)=dct2(a(:,:,1));
Z(:,:,2)=dct2(a(:,:,2));
Z(:,:,3)=dct2(a(:,:,3));

for i=1:100
    for j=1:100
        if((i+j)>100)
            Z(i,j,1)=0;
            Z(i,j,2)=0;
            Z(i,j,3)=0;
        end
    end
end
K(:,:,1)=idct2(Z(:,:,1));
K(:,:,2)=idct2(Z(:,:,2));
K(:,:,3)=idct2(Z(:,:,3));
subplot(2,4,2);
%imshow(Z);
imshow(uint8(K));
title('50% compression');

Z(:,:,1)=dct2(a(:,:,1));
Z(:,:,2)=dct2(a(:,:,2));
Z(:,:,3)=dct2(a(:,:,3));

for i=1:100
    for j=1:100
        if((i+j)>140)
            Z(i,j,1)=0;
            Z(i,j,2)=0;
            Z(i,j,3)=0;
        end
    end
end
K(:,:,1)=idct2(Z(:,:,1));
K(:,:,2)=idct2(Z(:,:,2));
K(:,:,3)=idct2(Z(:,:,3));
subplot(2,4,3);
%imshow(Z);
imshow(uint8(K));
title('30% compression');

Z(:,:,1)=dct2(a(:,:,1));
Z(:,:,2)=dct2(a(:,:,2));
Z(:,:,3)=dct2(a(:,:,3));

for i=1:100
    for j=1:100
        if((i+j)>180)
            Z(i,j,1)=0;
            Z(i,j,2)=0;
            Z(i,j,3)=0;
        end
    end
end
K(:,:,1)=idct2(Z(:,:,1));
K(:,:,2)=idct2(Z(:,:,2));
K(:,:,3)=idct2(Z(:,:,3));
subplot(2,4,4);
%imshow(Z);
imshow(uint8(K));
title('10% compression');

%FFT
Z(:,:,1)=fft2(a(:,:,1));
Z(:,:,2)=fft2(a(:,:,2));
Z(:,:,3)=fft2(a(:,:,3));


for i=1:100
    for j=1:100
        if((i+j)>60)
            Z(i,j,1)=0;
            Z(i,j,2)=0;
            Z(i,j,3)=0;
        end
    end
end
K(:,:,1)=ifft2(Z(:,:,1));
K(:,:,2)=ifft2(Z(:,:,2));
K(:,:,3)=ifft2(Z(:,:,3));
subplot(2,4,5);
%imshow(Z);
imshow(uint8(K));
title('70% compression FFT');

Z(:,:,1)=fft2(a(:,:,1));
Z(:,:,2)=fft2(a(:,:,2));
Z(:,:,3)=fft2(a(:,:,3));

for i=1:100
    for j=1:100
        if((i+j)>100)
            Z(i,j,1)=0;
            Z(i,j,2)=0;
            Z(i,j,3)=0;
        end
    end
end
K(:,:,1)=ifft2(Z(:,:,1));
K(:,:,2)=ifft2(Z(:,:,2));
K(:,:,3)=ifft2(Z(:,:,3));
subplot(2,4,6);
%imshow(Z);
imshow(uint8(K));
title('50% compression FFT');

Z(:,:,1)=fft2(a(:,:,1));
Z(:,:,2)=fft2(a(:,:,2));
Z(:,:,3)=fft2(a(:,:,3));

for i=1:100
    for j=1:100
        if((i+j)>140)
            Z(i,j,1)=0;
            Z(i,j,2)=0;
            Z(i,j,3)=0;
        end
    end
end
K(:,:,1)=ifft2(Z(:,:,1));
K(:,:,2)=ifft2(Z(:,:,2));
K(:,:,3)=ifft2(Z(:,:,3));
subplot(2,4,7);
%imshow(Z);
imshow(uint8(K));
title('30% compression FFT');

Z(:,:,1)=fft2(a(:,:,1));
Z(:,:,2)=fft2(a(:,:,2));
Z(:,:,3)=fft2(a(:,:,3));

for i=1:100
    for j=1:100
        if((i+j)>180)
            Z(i,j,1)=0;
            Z(i,j,2)=0;
            Z(i,j,3)=0;
        end
    end
end
K(:,:,1)=ifft2(Z(:,:,1));
K(:,:,2)=ifft2(Z(:,:,2));
K(:,:,3)=ifft2(Z(:,:,3));
subplot(2,4,8);
%imshow(Z);
imshow(uint8(K));
title('10% compression FFT'); 
 
OUTPUT :




OUTPUT : compressed image









Original Image






















































Comments









  1. v.sasidharreddyDecember 1, 2012 at 5:58 AM
    o = imread ('off stuff(F:):\downloads:\tat.jpg');
     
    w = size (o, 2);
     
    samplesHalf = floor(w / 2);
     
    samplesQuarter = floor(w / 4);
     
    samplesEighth = floor(w / 8);
     
    ci2 = [];
     
    ci4 = [];
     
    ci8 = [];
    for   k = 1:3% all color layers: RGB
    for  i = 1:size(o, 1)% all rows
     
    rowDCT = dct(double(o(i,:,k)));
     
    ci2(i,:,k) = idct(rowDCT(1:samplesHalf), w);
     
    ci4(i,:,k) = idct(rowDCT(1:samplesQuarter), w);
     
    ci8(i,:,k) = idct(rowDCT(1:samplesEighth), w);
     
    end
     
    end

    h = size(o, 1);
     
    samplesHalf = floor(h / 2);
     
    samplesQuarter = floor(h / 4);
     
    samplesEighth = floor(h / 8);
     


    ci2f = [];
     
    ci4f = [];
     
    ci8f = [];

    for k=1:3% all color layers:RGB
     
    for i=1:size(o, 2)% all columnsJECT:

    IMAGE COMPRESSION USING DISCRETE COSINE TRANFORM IMPLEMENTING MATLAB

    columnDCT2=dct(double(ci2(:,i,k)));
     
    columnDCT4=dct(double(ci4(:,i,k)));
     
    columnDCT8=dct(double(ci8(:,i,k)));
     
    ci2f(:,i,k) = idct(columnDCT2(1:samplesHalf), h);
     
    ci4f(:,i,k) = idct(columnDCT4(1:samplesQuarter), h);
     
    ci8f(:,i,k) = idct(columnDCT8(1:samplesEighth), h);
     
    end
     
    end
     subplot(2,2,1), image(uint8(o)), title('Original Image');
    subplot(2,2,2), image(uint8(ci2)), title('Compression Factor 2');
    subplot(2,2,3), image(uint8(ci4)), title('Compression Factor 4');
    subplot(2,2,4), image(uint8(ci8)), title('Compression Factor 8');
    figure

    subplot(2,2,1), image(uint8(o)), title('Original Image');
    subplot(2,2,2), image(uint8(ci2f)), title('Compression Factor 2 * 2');
    subplot(2,2,3), image(uint8(ci4f)), title('Compression Factor 4 * 4');
    subplot(2,2,4), image(uint8(ci8f)), title('Compression Factor 8 * 8');
       

    can u just guide what is mistake in this code for image compression using  dct  and how to correct this
    ReplyDelete
  2. UnknownNovember 13, 2016 at 7:51 AM
    no  mistake it is working 100%
    ReplyDelete











Post a Comment