function [r, c] = houghpixels(f, theta, rho, rbin, cbin)
%HOUGHPIXELS Compute image pixels belonging to Hough transform bin.
%   [R, C] = HOUGHPIXELS(F, THETA, RHO, RBIN, CBIN) computes the
%   row-column indices (R, C) for nonzero pixels in image F that map
%   to a particular Hough transform bin, (RBIN, CBIN).  RBIN and CBIN
%   are scalars indicating the row-column bin location in the Hough
%   transform matrix returned by function HOUGH.  THETA and RHO are
%   the second and third output arguments from the HOUGH function.

%   Copyright 2002-2004 R. C. Gonzalez, R. E. Woods, & S. L. Eddins
%   Digital Image Processing Using MATLAB, Prentice-Hall, 2004
%   $Revision: 1.4 $  $Date: 2003/10/26 22:35:03 $

[x, y, val] = find(f);
x = x - 1; y = y - 1;

theta_c = theta(cbin) * pi / 180;
rho_xy = x*cos(theta_c) + y*sin(theta_c);
nrho = length(rho);
slope = (nrho - 1)/(rho(end) - rho(1));
rho_bin_index = round(slope*(rho_xy - rho(1)) + 1);

idx = find(rho_bin_index == rbin);

r = x(idx) + 1; c = y(idx) + 1;