matlab：归一化距离图

Question

我想取一个位置网格，然后计算每个像素的归一化距离。我不知道这是做正确的方式：

clear all; 
im = imread('test1.png');     % read in the image 
im = im(:,:,1);        %vectorize image 

n = size(im,1); % No of grids in the X-Y plane 

xp(1:n)=1:1:n; % Y-coordinates of the plane where we are interested 
yp(1:n)=1:1:n;% X-coordinates of the plane where we are interested 

Y(1:n,1:n)=0; % This array is for 1-d to 2-d conversion of coordinates 
X(1:n,1:n)=0; 

for i=1:n 
    Y(i,:)=yp(i); % all y-coordinates value in 2-d form 
end 
for i=1:n 
    X(:,i)=xp(i);% all x-coordinates value in 2-d form 
end 

Z = zeros(size(X)); % Z dimension is appended to 0 

pos = [X(:),Y(:),Z(:)];  %position co-ordinates for x y z dimensions 

N = size(pos,1);    % size of position matrix 
v = cell(N,1);     %define cell for storage of x-y plane direction vectors 
for j = 1:N 
    for i = 1:N 
     vecdir(i,:) = pos(i,:) - pos(j,:);    %direction of vectors between each point in the x-y plane 
     dist(i,:) = pdist2(pos(i,:),pos(j,:));   %distance between each point in the x-y plane 
     norm(i,:) = vecdir(i,:)./(dist(i,:)).^2;   %normalised distance between each point in the x-y plane 
    end 
    v{j} = vecdir; 
    d{j} = dist; 
    r{j} = norm;           %store normalised distances into a cell array 

end 

R = cellfun(@isnan,r,'Un',0); 
for ii = 1:length(r) 
r{ii}(R{ii}) =0; 
end 

在那里，如果我拿第一像素的3×3的图像（大小（IM））我得到的标准化距离到所有其它像素（在XYZ位置格式）为：

>> r{1} 

ans = 

     0   0   0 
     0 1.0000   0 
     0 0.5000   0 
    1.0000   0   0 
    0.5000 0.5000   0 
    0.2000 0.4000   0 
    0.5000   0   0 
    0.4000 0.2000   0 
    0.2500 0.2500   0 

我只是想知道，如果我这样做的正确的方式（在这个阶段不要太费心约效率）

Answer 1

不是一个问题的答案，但此言约代码：

的xp，yp，X和Y整个初始化可以更容易地与meshgrid来完成：

xp=1:n; 
yp=xp; 
[X,Y]=meshgrid(xp,yp); 

就问题本身：

vecdir(i,:) = pos(i,:) - pos(j,:);    %direction of vectors between each point in the x-y plane 
dist(i,:) = pdist2(pos(i,:),pos(j,:));   %distance between each point in the x-y plane 
norm(i,:) = vecdir(i,:)./(dist(i,:)).^2;   %normalised distance between each point in the x-y plane 

我不会用 '规范' 作为变量名称，因为它也是function

vecdir是正确的; dist也不过essentialy，它应该是一样norm(vecdir(i,:),2)（功能norm()，不是你的变量！）

运用这一yiels：

vecdir(i,:) = pos(i,:) - pos(j,:); 
normvec = vecdir(i,:)./norm(vecdir(i,:),2); 

这是海事组织how you usually normalize a vector。你得到了正确的结果，当然，但使用pdist2是没有必要的，因为你已经有了距离矢量，你只需要对它进行归一化。