www.pudn.com > 图像压缩的几个MATLAB算法.zip > dctcompr.m

function [im] = dctcompr (infile,coeff,outfile) 
% DCTCOMPR (infile,coeff,outfile) 
% Image compression based on Discrete Cosine Transform. 
%  infile is input file name present in the current directory 
%  coeff is the number of coefficients with the most energy 
%  outfile is output file name which will be created 
% 
% Example of use: 
% out=imcompr('input_image.bmp',2000,'output_image.bmp'); 
%  
% The input image A can be RGB or GRAYSCALE. 
% 
% RGB case: 
% If A is of class double, all values must be in the range [0,1], 
% and A must be m-by-n-by-3. 
% If A is of class uint16 or uint8, A must be m-by-n-by-3. 
% The same number of coefficients are selected for each component 
% (red, green and blue). 
% 
% GRAYSCALE case: 
% If A is of class double, all values must be in the range [0,1],  
% and the number of dimensions of A must be 2. If A is of class 
% uint16 or uint8, the number of dimensions of A must be 2. 
% uint16 or double. 
% 
%  
%  
% 
% References: 
% 
% For more details concernings the algorithm implemented please visit the following links: 
%  
%  http://www.mathworks.com/matlabcentral/fileexchange/loadFile.do?objectId=4328&objectType=file 
%  
%  http://www.ece.purdue.edu/~ace/jpeg-tut/jpegtut1.html 
%  
% Please contribute if you find this software useful. 
% Report bugs to luigi.rosa@tiscali.it 
% 
% 
%***************************************************************** 
% Luigi Rosa 
% Via Centrale 27 
% 67042 Civita di Bagno 
% L'Aquila --- ITALY  
% email  luigi.rosa@tiscali.it 
% mobile +39 340 3463208  
% http://utenti.lycos.it/matlab 
%***************************************************************** 
% 
% 
if (exist(infile)==2) 
    a = imread(infile); 
    figure('Name','Input image'); 
    imshow(a); 
else 
    warndlg('The file does not exist.',' Warning '); 
    im=[]; 
    return 
end 
 
 
if isrgb(a)   
     
    if isa(a(:,:,1),'uint8') 
        red = double(a(:,:,1)); 
        green = double(a(:,:,2)); 
        blue = double(a(:,:,3)); 
         
        red_dct=dct2(red); 
        green_dct=dct2(green); 
        blue_dct=dct2(blue); 
         
        red_pow   = red_dct.^2; 
        green_pow = green_dct.^2; 
        blue_pow  = blue_dct.^2; 
         
        red_pow=red_pow(:); 
        green_pow=green_pow(:); 
        blue_pow=blue_pow(:); 
         
        [B_r,index_r]=sort(red_pow); 
        [B_g,index_g]=sort(green_pow); 
        [B_b,index_b]=sort(blue_pow); 
         
        index_r=flipud(index_r); 
        index_g=flipud(index_g); 
        index_b=flipud(index_b); 
         
        im_dct_r=zeros(size(red)); 
        im_dct_g=zeros(size(green)); 
        im_dct_b=zeros(size(blue)); 
         
        for ii=1:coeff 
            im_dct_r(index_r(ii))=red_dct(index_r(ii)); 
            im_dct_g(index_g(ii))=green_dct(index_g(ii)); 
            im_dct_b(index_b(ii))=blue_dct(index_b(ii)); 
        end 
         
        im_r=idct2(im_dct_r); 
        im_g=idct2(im_dct_g); 
        im_b=idct2(im_dct_b); 
         
        im=zeros(size(red,1),size(red,2),3); 
        im(:,:,1)=im_r; 
        im(:,:,2)=im_g; 
        im(:,:,3)=im_b; 
         
        im=uint8(im); 
         
        imwrite(im, outfile);        
         
         
        figure('Name','Output image'); 
        imshow(im); 
         
        return; 
    end 
     
    if isa(a(:,:,1),'uint16') 
        red = double(a(:,:,1)); 
        green = double(a(:,:,2)); 
        blue = double(a(:,:,3)); 
         
        red_dct=dct2(red); 
        green_dct=dct2(green); 
        blue_dct=dct2(blue); 
         
        red_pow   = red_dct.^2; 
        green_pow = green_dct.^2; 
        blue_pow  = blue_dct.^2; 
         
        red_pow=red_pow(:); 
        green_pow=green_pow(:); 
        blue_pow=blue_pow(:); 
         
        [B_r,index_r]=sort(red_pow); 
        [B_g,index_g]=sort(green_pow); 
        [B_b,index_b]=sort(blue_pow); 
         
        index_r=flipud(index_r); 
        index_g=flipud(index_g); 
        index_b=flipud(index_b); 
         
        im_dct_r=zeros(size(red)); 
        im_dct_g=zeros(size(green)); 
        im_dct_b=zeros(size(blue)); 
         
        for ii=1:coeff 
            im_dct_r(index_r(ii))=red_dct(index_r(ii)); 
            im_dct_g(index_g(ii))=green_dct(index_g(ii)); 
            im_dct_b(index_b(ii))=blue_dct(index_b(ii)); 
        end 
         
        im_r=idct2(im_dct_r); 
        im_g=idct2(im_dct_g); 
        im_b=idct2(im_dct_b); 
         
        im=zeros(size(red,1),size(red,2),3); 
        im(:,:,1)=im_r; 
        im(:,:,2)=im_g; 
        im(:,:,3)=im_b; 
         
        im=uint16(im); 
         
        imwrite(im, outfile);        
         
         
        figure('Name','Output image'); 
        imshow(im); 
         
         
        return; 
    end 
     
    if isa(a(:,:,1),'double') 
        red = double(a(:,:,1)); 
        green = double(a(:,:,2)); 
        blue = double(a(:,:,3)); 
         
        red_dct=dct2(red); 
        green_dct=dct2(green); 
        blue_dct=dct2(blue); 
         
        red_pow   = red_dct.^2; 
        green_pow = green_dct.^2; 
        blue_pow  = blue_dct.^2; 
         
        red_pow=red_pow(:); 
        green_pow=green_pow(:); 
        blue_pow=blue_pow(:); 
         
        [B_r,index_r]=sort(red_pow); 
        [B_g,index_g]=sort(green_pow); 
        [B_b,index_b]=sort(blue_pow); 
         
        index_r=flipud(index_r); 
        index_g=flipud(index_g); 
        index_b=flipud(index_b); 
         
        im_dct_r=zeros(size(red)); 
        im_dct_g=zeros(size(green)); 
        im_dct_b=zeros(size(blue)); 
         
        for ii=1:coeff 
            im_dct_r(index_r(ii))=red_dct(index_r(ii)); 
            im_dct_g(index_g(ii))=green_dct(index_g(ii)); 
            im_dct_b(index_b(ii))=blue_dct(index_b(ii)); 
        end 
         
        im_r=idct2(im_dct_r); 
        im_g=idct2(im_dct_g); 
        im_b=idct2(im_dct_b); 
         
        im=zeros(size(red,1),size(red,2),3); 
        im(:,:,1)=im_r; 
        im(:,:,2)=im_g; 
        im(:,:,3)=im_b; 
         
        imwrite(im, outfile);        
         
        figure('Name','Output image'); 
        imshow(im); 
        return; 
    end 
end 
 
if isgray(a) 
     
    dvalue=double(a); 
     
     
    if isa(a,'uint8') 
        img_dct=dct2(dvalue); 
        img_pow=(img_dct).^2; 
        img_pow=img_pow(:); 
        [B,index]=sort(img_pow); 
        B=flipud(B); 
        index=flipud(index); 
         
        compressed_dct=zeros(size(dvalue)); 
        for ii=1:coeff 
            compressed_dct(index(ii))=img_dct(index(ii)); 
        end 
        im=idct2(compressed_dct); 
        im=uint8(im); 
    end 
     
    if isa(a,'uint16') 
        img_dct=dct2(dvalue); 
        img_pow=(img_dct).^2; 
        img_pow=img_pow(:); 
        [B,index]=sort(img_pow); 
        B=flipud(B); 
        index=flipud(index); 
         
        compressed_dct=zeros(size(dvalue)); 
        for ii=1:coeff 
            compressed_dct(index(ii))=img_dct(index(ii)); 
        end 
        im=idct2(compressed_dct); 
        im=uint16(im); 
         
    end 
     
    if isa(a,'double') 
        img_dct=dct2(dvalue); 
        img_pow=(img_dct).^2; 
        img_pow=img_pow(:); 
        [B,index]=sort(img_pow); 
        B=flipud(B); 
        index=flipud(index); 
         
        compressed_dct=zeros(size(dvalue)); 
        for ii=1:coeff 
            compressed_dct(index(ii))=img_dct(index(ii)); 
        end 
        im=idct2(compressed_dct); 
         
    end 
     
    imwrite(im, outfile); 
    figure('Name','Output image'); 
    imshow(im); 
    return; 
end