广义霍夫R表

Question

我正在尝试实现MATLAB this paper中提出的广义Hough变换。我也尝试使用this document来了解算法。我一直想弄清楚如何计算坡度角以找到要在R表中使用的Φ。

我已经尝试运行此matlab implementation，但是轮廓函数尝试访问负索引。缺少的功能如下。

distance.m

function [ d ] = distance( x1, y1, x2, y2 )
  d = sqrt( (x2-x1)^2 + (y2-y1)^2 );   
end

barycenter.m

function [ xo, yo ] = barycenter( img )
%   gravitational center coordinates of a shape 

  [rows, cols] = size(img);
  x = ones(rows, 1)*(1:cols);
  y = (1:rows)'*ones(1,cols);
  area = sum(sum(img));
  xo = sum(sum(double(img) .* x)) / area;
  yo = sum(sum(double(img) .* y)) / area;

end

modelHough.m

function [H]=ModelHough(imgRGB)
% Generalized Hough Transform Modeling

% Image Binarization
imgBW = rgb2gray(imgRGB);
imgBI = imgBW < 255;

% Retrieving information about the contour: points and number (N)
N = contour(imgBI);

% Model initialization:
    % row = beta value * 100
    % column = number of the couple (alpha, distance)
    % 3rd dimension: 1 = alpha, 2 = distance
H=zeros(round(100*2*pi),N,2);

% Compute of the barycenter coordinates
[ xo, yo ] = barycenter(imgBI);

% for each contour point
for i=1:N

    % beta compute for ith contour point
    b = beta(N, imgBI, i);

    % research of the first column
    k=1;
    while H(b+1,k,2)~=0
       k=k+1;
    end

    % compute of the alpha value
    H(b+1, k, 1) = alpha(N, i, imgBI);

    % compute of the distance value
    H(b+1, k, 2) = distance( xo, yo, i, b );

end

Answer 1

使用合适的边缘检测器。您可以从Sobel operator开始。倾斜角为atan（Gy / Gx），如Wiki文章中所述。

Answer 2

如果使用公共边缘检测器检测边缘，则应将第14行的countor.m更改为如下所示：

while (img(i,j)~=1)