[Octave-bug-tracker] [bug #54874] [octave forge] (image) hough transform size is not compatible with Matlab

[Avinoam Kalma]

URL:
  <https://savannah.gnu.org/bugs/?54874>

                 Summary: [octave forge] (image) hough transform size is not
compatible with Matlab
                 Project: GNU Octave
            Submitted by: avinoam
            Submitted on: Mon 22 Oct 2018 04:12:06 AM UTC
                Category: Octave Forge Package
                Severity: 3 - Normal
                Priority: 5 - Normal
              Item Group: Matlab Compatibility
                  Status: None
             Assigned to: None
         Originator Name: 
        Originator Email: 
             Open/Closed: Open
         Discussion Lock: Any
                 Release: other
        Operating System: Any

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Details:

Matlab:


>> size(hough (zeros(10)))

ans =

    27   180

>> size(hough (zeros(20)))

ans =

    55   180


Octave:


>> size(hough (zeros(10)))

ans =

    29   180

>> size(hough (zeros(20)))

ans =

    57   180


According to Matlab documentation
(https://www.mathworks.com/help/images/ref/hough.html)
The Hough transform matrix, H, is nrho-by-ntheta where:


nrho = 2*(ceil(D/RhoResolution)) + 1, and 
D = sqrt((numRowsInBW - 1)^2 + (numColsInBW - 1)^2). 


While hough_line.cc set the size as:


Matrix size (1, 2); 
size (0) = r; size (1) = c; 
const double diag_length = sqrt (size.sumsq ()(0)); 
const int nr_bins = 2 * (int)ceil (diag_length) - 1; 


Which should be changes to 


const double diag_length = sqrt ((c-1)*(c-1)+(r-1)*(r-1)); 
const int nr_bins = 2 * (int)ceil (diag_length) + 1; 


This change makes hough tests compatible with matlab 






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