imlogpolar.m

介绍了傅立叶变换的基本原理

function [rout,g,b] = imlogpolar(varargin) 
>IMLOGPOLAR Compute logarithmic polar transformation of image. 
> B = IMLOGPOLAR(A,NRHO,NTHETA,METHOD) computes the logarithmic 
> polar transformation of image A, generating a log polar image 
> of size NRHO by NTHETA. METHOD describes the interpolation 
> method. METHOD is a string that can have one of these values: 
> 
> 'nearest' (default) nearest neighbor interpolation 
> 
> 'bilinear' bilinear interpolation 
> 
> 'bicubic' bicubic interpolation 
> 
> If you omit the METHOD argument, IMLOGPOLAR uses the default 
> method of 'nearest'. 
> 
> B = IMLOGPOLAR(A,NRHO,NTHETA,METHOD,CTR) assumes that the 2x1 
> vector CTR contains the coordinates of the origin in image A. 
> If CTR is not supplied, the default is CTR = [(m+1)/2,(n+1)/2], 
> where A has n rows and m columns. 
> 
> B = IMLOGPOLAR(A,NRHO,NTHETA,METHOD,CTR,SHAPE) where SHAPE is a 
> string that can have one of these values: 
> 
> 'full' - returns log polar transformation containing ALL 
> pixels from image A (the circumscribed circle 
> centered at CTR) 
> 
> 'valid' - returns log polar transformation containing only 
> pixels from the largest inscribed circle in image A 
> centered at CTR. 
> 
> If you omit the SHAPE argument, IMLOGPOLAR uses the default shape 
> of 'valid'. If you specify the shape 'full', invalid values on the 
> periphery of B are set to NaN. 
> 
> Class Support 
> ------------- 
> The input image can be of class uint8 or double. The output 
> image is of the same class as the input image. 
> 
> Example 
> ------- 
> I = imread('ic.tif'); 
> J = imlogpolar(I,64,64,'bilinear'); 
> imshow(I), figure, imshow(J) 
> 
> See also IMCROP, IMRESIZE, IMROTATE. 

> Nathan D. Cahill 8-16-01, modified from: 
> Clay M. Thompson 8-4-92 
> Copyright 1993-1998 The MathWorks, Inc. All Rights Reserved. 
> $Revision: 5.10 $ $Date: 1997/11/24 15:35:33 $ 

> Grandfathered: 
> Without output arguments, IMLOGPOLAR(...) displays the transformed 
> image in the current axis. 

[Image,rows,cols,Nrho,Ntheta,Method,Center,Shape,ClassIn] = parse_inputs(varargin{:}); 

threeD = (ndims(Image)==3); > Determine if input includes a 3-D array 

if threeD, 
[r,g,b] = transformImage(Image,rows,cols,Nrho,Ntheta,Method,Center,Shape); 
if nargout==0, 
imshow(r,g,b); 
return; 
elseif nargout==1, 
if strcmp(ClassIn,'uint8'); 
rout = repmat(uint8(0),[size(r),3]); 
rout(:,:,1) = uint8(round(r*255)); 
rout(:,:,2) = uint8(round(g*255)); 
rout(:,:,3) = uint8(round(b*255)); 
else 
rout = zeros([size(r),3]); 
rout(:,:,1) = r; 
rout(:,:,2) = g; 
rout(:,:,3) = b; 
end 
else > nargout==3 
if strcmp(ClassIn,'uint8') 
rout = uint8(round(r*255)); 
g = uint8(round(g*255)); 
b = uint8(round(b*255)); 
else 
rout = r; > g,b are already defined correctly above 
end 
end 
else 
r = transformImage(Image,rows,cols,Nrho,Ntheta,Method,Center,Shape); 
if nargout==0, 
imshow(r); 
return; 
end 
if strcmp(ClassIn,'uint8') 
if islogical(Image) 
r = im2uint8(logical(round(r))); 
else 
r = im2uint8(r); 
end 
end 
rout = r; 
end