On 21 October 2012 15:54, <giorgio.denun...@unisalento.it> wrote:
> Hi Carnė,
> thanks for your kind reply! I'll immediately check the changes in the pkg.
>
> I prefer to send my reply to the list too, because it might be useful to
> other people who are using or will use graycomatrix in octave (before it
> gets aligned with matlab's).
>
> As to the differences between matlab and octave versions of graycomatrix,
> here are some (as far as I can see at present):
>
> input parameters:
> 1) matlab wants vectors, one row for each distance/direction couple, and
> the necessary information is a vector with x- and y- components,
> describing the particular relative-position vector(s) we are interested in
> ('Offset' parameter) (no idea if I was clear… perhaps it is better to try
> matlab help :-) ; octave wants distinct angles (degrees) and distances:
> offsets = [0 1; 0 -1; -1 1; 1 -1; -1 0; 1 0; -1 -1; 1 1];
> % matlab
> angles = [6 ; 2 ; 5 ; 1 ; 4 ; 0 ; 3 ; 7] * pi/4; distances = [1];
> % octave
>
> 2) matlab implicitly transforms the input-image bit depth ('NumLevels'
> parameter), while octave needs that you change it beforehand; matlab wants
> to know the limits of gray level values ('GrayLimits' parameter), octave
> does not (I do not know if it assumes the whole range of possible values
> in accordance with the bit depth, or it calculates min and max from the
> image data (I suppose the former is correct, but I have not checked yet).
> Octave just wants to know how many levels are there (not their values).
> Anyway I still have to totally verify this. The output is also different
> because octave gives a 4D matrix (numlevels x numlevels x distances x
> angles, iirc), while matlab gives a 3D matrix:
>
> numlevels = 16;
> graylimits = [0, 65535];
>
> % matlab
> theglcm = graycomatrix(I ,'Offset', offsets, 'NumLevels', numlevels ,
> 'GrayLimits', graylimits);
>
> % octave
> IOct = uint16(floor(numlevels*(double(I)/graylimits(2)))); %
> diminuish bit depth; I supposed graylimits(1) to be zero.
> theglcm = graycomatrix(IOct, numlevels, distances, angles);
> theglcm = squeeze(theglcm); % This works only because I am working
> with just one distance value! Now the output is numlevels x numlevels
> x angles like in matlab
>
> I hope I made no mistakes in what I wrote… If I did please be patient...
>
> Thanks again for your work!
> Best regards
> Giorgio
Hi Giorgio
are you able to submit a patch for this? While most of the functions
are written in the very own octave language and should be no problem,
graycomatrix was implemented is written in C++. If you can't fix this,
could you please report this as a bug at
https://sourceforge.net/p/octave/bugs/ so it's not forgotten?
Thanks,
Carnë
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