www.pudn.com > 图像压缩的几个MATLAB算法.zip > conv2fft.m

function [out] = conv2fft(z1,z2,shape,shape2) 
%CONV2FFT FFT-based two dimensional convolution. 
%    C = CONV2FFT(A, B) performs the 2-D convolution of matrices 
%    A and B.   If [ma,na] = size(A) and [mb,nb] = size(B), then 
%    size(C) = [ma+mb-1,na+nb-1]. 
%    C = CONV2FFT(H1, H2, A) convolves A first with the vector H1  
%    along the rows and then with the vector H2 along the columns. 
%  
%    C = CONV2FFT( ... ,'shape') returns a subsection of the 2-D 
%    convolution with size specified by 'shape': 
%      'full'  - (default) returns the full 2-D convolution, 
%      'same'  - returns the central part of the convolution 
%                that is the same size as A. 
%      'valid' - returns only those parts of the convolution 
%                that are computed without the zero-padded 
%                edges. size(C) = [ma-mb+1,na-nb+1] when 
%                all(size(A) >= size(B)), otherwise C is empty. 
% 
% 
% 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 
%***************************************************************** 
% 
 
 
 
%-------------------------------------------------------------------------- 
%-------------------------------------------------------------------------- 
% 3 input arguments: matrix 1, matrix 2, shape 
if ((nargin==3)&&(isa(shape,'char')))  
    if strcmp(shape,'same') 
        z1x=size(z1,1); 
        z1y=size(z1,2); 
        z2x=size(z2,1); 
        z2y=size(z2,2); 
         
        if any(any(imag(z1)))||any(any(imag(z2))) 
            out=(ifft2(fft2(z1,z1x+z2x-1,z1y+z2y-1).*fft2(z2,z1x+z2x-1,z1y+z2y-1))); 
        else 
            out=real(ifft2(fft2(z1,z1x+z2x-1,z1y+z2y-1).*fft2(z2,z1x+z2x-1,z1y+z2y-1))); 
        end 
         
         
        px=((z2x-1)+mod((z2x-1),2))/2; 
        py=((z2y-1)+mod((z2y-1),2))/2; 
         
        out=out(px+1:px+z1x,py+1:py+z1y); 
        return; 
    end 
     
    if strcmp(shape,'full') 
        z1x=size(z1,1); 
        z1y=size(z1,2); 
        z2x=size(z2,1); 
        z2y=size(z2,2); 
         
        if any(any(imag(z1)))||any(any(imag(z2))) 
            out=(ifft2(fft2(z1,z1x+z2x-1,z1y+z2y-1).*fft2(z2,z1x+z2x-1,z1y+z2y-1))); 
        else 
            out=real(ifft2(fft2(z1,z1x+z2x-1,z1y+z2y-1).*fft2(z2,z1x+z2x-1,z1y+z2y-1))); 
        end 
         
        return; 
    end 
     
    if strcmp(shape,'valid') 
        z1x=size(z1,1); 
        z1y=size(z1,2); 
        z2x=size(z2,1); 
        z2y=size(z2,2); 
        if ((z1xoutx)||(dimy>outy)||(dimx+lx-1>outx)||(dimy+ly-1>outy) 
                out=[]; 
                return; 
            else                 
                out=out(dimx:dimx+lx-1,dimy:dimy+ly-1); 
                return; 
            end            
        end 
        %---------------------------------------------         
        if strcmp(shape2,'same') 
            lx=ax; 
            ly=ay; 
            px=((dimx-1)+mod((dimx-1),2))/2; 
            py=((dimy-1)+mod((dimy-1),2))/2; 
             
            out=out(px+1:px+ax,py+1:py+ay);             
            return; 
        end 
        %---------------------------------------------           
         
    end 
    %------------------------- 
end