对数极坐标变换MATLAB代码

http://www.vision.ee.ethz.ch/~konrads/code/logpolar.m function [I_lp,I_nearest,I_bilinear] = logpolar(I,slices) % % [I_lp,I_nearest,I_bilinear] = logpolar(I,slices) % % Log-polar resampling of an image, and back-sampling to retinal plane % % INPUT: % I ... source image % slices ... number of radial slices % % OUTPUT: % I_lp ... the log-polar image % I_nearest ... backprojection, nearest-neighbor resampling (shows log-polar pixels) % I_bilinear ... backprojection, bilinear resampling (smooth image with varying resolution) % % Konrad, 22.09.2006 I = double(I); [rows,cols,planes] = size(I); %%%%%%%%%%%%%%%%%%% % log-polar mapping %%%%%%%%%%%%%%%%%%% ctr = [rows cols]/2; mult = 1+2*pi/slices; % make empty log-polar image lpcols = slices; lprows = floor(log(max(ctr)*sqrt(2))/log(mult)); I_lp = zeros(lpcols,lprows,planes,'uint8'); % fill pixels for u = 1:lpcols for v = 1:lprows % find the center of the log-polar bin in the original image ang = u/slices*2*pi; pt = ctr+mult^v*[cos(ang) sin(ang)]; pt = round(pt); if pt(1)<1 || pt(2)<1 || pt(1)>rows || pt(2)>cols, continue; end % integrate over log-polar pixel rd = mult^v-mult^(v-1); sz = ceil(rd); if sz<1 filt = 1; bbximg = [ pt ; pt ]; else filt = fspecial('disk',sz); bbximg = [ pt-[sz sz] ; pt+[sz sz] ]; bbxflt = [ 1 1 ; 2*[sz sz]+[1 1] ]; if bbximg(1,1)>rows || bbximg(1,2)<1 || bbximg(2,1)>cols || bbximg(2,2)<1 continue; end % correct for pixels overlapping the image boundary if bbximg(1,1)<1, bbxflt(1,1) = 2-bbximg(1,1); bbximg(1,1) = 1; end if bbximg(1,2)<1, bbxflt(1,2) = 2-bbximg(1,2); bbximg(1,1) = 1; end if bbximg(2,1)>rows, bbxflt(2,1) = bbxflt(2,1)-bbximg(2,1)+rows; bbximg(2,1) = rows; end if bbximg(2,2)>cols, bbxflt(2,2) = bbxflt(2,2)-bbximg(2,2)+cols; bbximg(2,2) = cols; end filt = filt(bbxflt(1,1):bbxflt(2,1),bbxflt(1,2):bbxflt(2,2)); filt = filt/sum(sum(filt)); end for p = 1:planes val = I(bbximg(1,1):bbximg(2,1),bbximg(1,2):bbximg(2,2),p).*filt; I_lp(u,v,p) = uint8(sum(val(:))); end end end % move 360 degrees to 0 I_lp = [I_lp(2:end,:,:) ; I_lp(1,:,:)]; %%%%%%%%%%%%%%%%%%%%%%%%%%% % back-projection to retina %%%%%%%%%%%%%%%%%%%%%%%%%%% % circular extension of log-polar image lpcols = lpcols+1; I_lpbig = [I_lp;I_lp(1,:,:)]; % make empty images I_nearest = zeros(rows,cols,planes,'uint8'); I_bilinear = zeros(rows,cols,planes,'uint8'); % fill pixels for u = 1:rows for v = 1:cols % get log-polar coordinate uu = u-ctr(1); vv = v-ctr(2); rfloat = 0.5*log(max(1,uu^2+vv^2))/log(mult)-1.5; afloat = atan2(vv,uu)/(2*pi)*slices-1.5; ri = afloat<=1; afloat(ri) = slices+afloat(ri); % round for nearest neighbor rind = round(rfloat); aind = round(afloat); if afloat<1 || rfloat<1 || afloat>lpcols || rfloat>lprows, continue; end % get values for p = 1:planes I_nearest(u,v,p) = I_lpbig(aind,rind,p); af = floor(afloat); rf = floor(rfloat); I_bilinear(u,v,p) = interp2(I_lpbig(af:af+1,rf:rf+1,p),rfloat-rf+1,afloat-af+1,'*linear'); end end end http://blog.youkuaiyun.com/luhuillll/archive/2007/08/08/1732818.aspx % POLARTRANS - Transforms image to polar coordinates % % Usage:    pim = polartrans(im, nrad, ntheta, cx, cy, linlog, shape) % % Arguments: %           im     - image to be transformed. %           nrad   - number of radius values. %           ntheta - number of theta values. %           cx, cy - optional specification of origin. If this is not %                    specified it defaults to the centre of the image. %           linlog - optional string 'linear' or 'log' to obtain a %                    transformation with linear or logarithmic radius %                    values. linear is the default. %           shape - optional string 'full' or 'valid'