图像直角坐标系向对数极坐标转换的有关代码

发布时间：2011-11-24 21:39:20 来源：文档文库

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新的对数极变换的代码

%function[rout,g,b]=LHimlogpolar(image,Nrho,Ntheta,Method,Center,Shape)
function [rout,g,b] = LHimlogpolar(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.

% Outputs: A       the input image
%           Nrho    the desired number of rows of transformed image
%           Ntheta the desired number of columns of transformed image
%           Method interpolation method (nearest,bilinear,bicubic)
%           Center origin of input image
%           Shape   output size (full,valid)
%           Class   storage class of A
[Image,rows,cols,Nrho,Ntheta,Method,Center,Shape,ClassIn]=LHparse_inputs(varargin{:});
threeD = (ndims(Image)==3); % Determine if input includes a 3-D array

if threeD,
   [r,g,b] = LHtransformImage(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 = LHtransformImage(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

function [A,Ar,Ac,Nrho,Ntheta,Method,Center,Shape,Class] = LHparse_inputs(varargin)
% Outputs: A       the input image
%           Nrho    the desired number of rows of transformed image
%           Ntheta the desired number of columns of transformed image
%           Method interpolation method (nearest,bilinear,bicubic)
%           Center origin of input image
%           Shape   output size (full,valid)
%           Class   storage class of A
error(nargchk(3,6,nargin));

A = varargin{1};

Ar = size(A,1); % Ar = number of rows of the input image
Ac = size(A,2); % Ac = number of columns of the input image

Nrho = varargin{2};
Ntheta = varargin{3};
Class = class(A);

if nargin < 4
    Method = '';
else
    Method = varargin{4};
end
if isempty(Method)
    Method = 'nearest';
end
Method = lower(Method);
if ~any(strcmp(Method,{'nearest','bilinear','bicubic'}))
    error('Method must be one of ''nearest'', ''bilinear'', or ''bicubic''.');
end

if nargin < 5
    Center = [];
else
    Center = varargin{5};
end
if isempty(Center)
    Center = [(Ac+1)/2 (Ar+1)/2];
end
if length(Center(:))~=2
    error('Center should be 1x2 array.');
end
if any(Center(:)>[Ac;Ar] | Center(:)<1)
% THIS LINE USED TO READ 'ifany(Center(:)>[Ar;Ac] | Center(:)<1)' but Ar and Ac should be swapped round -- look at line 40 for whty this should be. A.I.Wilmer,12th Oct 2002
    num2str(['Center is',num2str(Center(1)),',',num2str(Center(2)),'with size of image =',num2str(Ar),'x',num2str(Ac),' (rows,columns)']);
    warning('Center supplied is not within image boundaries.');
end

if nargin < 6
    Shape = '';
else
    Shape = varargin{6};
end
if isempty(Shape)
    Shape = 'valid';
end
Shape = lower(Shape);
if ~any(strcmp(Shape,{'full','valid'}))
    error('Shape must be one of ''full'' or ''valid''.');
end

if isa(A, 'uint8'),     % Convert A to Double grayscale for interpolation
   if islogical(A)
      A = double(A);
   else
      A = double(A)/255;
   end
end

function [r,g,b] = LHtransformImage(A,Ar,Ac,Nrho,Ntheta,Method,Center,Shape)
% Inputs:   A       the input image
%           Nrho    the desired number of rows of transformed image
%           Ntheta the desired number of columns of transformed image
%           Method interpolation method (nearest,bilinear,bicubic)
%           Center origin of input image
%           Shape   output size (full,valid)
%           Class   storage class of A

global rho;
theta = linspace(0,2*pi,Ntheta+1); theta(end) = [];

switch Shape
case 'full'
    corners = [1 1;Ar 1;Ar Ac;1 Ac];
    d = max(sqrt(sum((repmat(Center(:)',4,1)-corners).^2,2)));
case 'valid'
    d = min([Ac-Center(1) Center(1)-1 Ar-Center(2) Center(2)-1]);
end
minScale = 1;
rho = logspace(log10(minScale),log10(d),Nrho)'; % default 'base 10' logspace - play with d to change the scale of the log axis

% convert polar coordinates to cartesian coordinates and center
xx = rho*cos(theta+pi) + Center(1);
yy = rho*sin(theta+pi) + Center(2);

if nargout==3
if strcmp(Method,'nearest'), % Nearest neighbor interpolation

      [xi,yi] = meshgrid(-3:.1:3,-3:.1:3)

    r=interp2(A(:,:,1),xx,yy,'nearest');
    g=interp2(A(:,:,2),xx,yy,'nearest');
    b=interp2(A(:,:,3),xx,yy,'nearest');
elseif strcmp(Method,'bilinear'), % Linear interpolation
    r=interp2(A(:,:,1),xx,yy,'linear');
    g=interp2(A(:,:,2),xx,yy,'linear');
    b=interp2(A(:,:,3),xx,yy,'linear');
elseif strcmp(Method,'bicubic'), % Cubic interpolation

    r=interp2(A(:,:,1),xx,yy,'cubic');
    g=interp2(A(:,:,2),xx,yy,'cubic');
    b=interp2(A(:,:,3),xx,yy,'cubic');
else
    error(['Unknown interpolation method: ',method]);
end
% any pixels outside , pad with black
mask= (xx>Ac) | (xx<1) | (yy>Ar) | (yy<1);
r(mask)=NaN;
g(mask)=NaN;
b(mask)=NaN;
else
   if strcmp(Method,'nearest'), % Nearest neighbor interpolation
    r=interp2(A,xx,yy,'nearest');
    %r=interp2(A,xx,yy,'nearest');
elseif strcmp(Method,'bilinear'), % Linear interpolation
      size(A)
    r=interp2(A,xx,yy,'linear');
    %r=interp2(A,xx,yy,'linear');
elseif strcmp(Method,'bicubic'), % Cubic interpolation
    r=interp2(A,xx,yy,'cubic');
    %r=interp2(A,xx,yy,'cubic');
else
    error(['Unknown interpolation method: ',method]);
end
% any pixels outside warp, pad with black
mask= (xx>Ac) | (xx<1) | (yy>Ar) | (yy<1);
r(mask)=NaN;
end