[Octave-bug-tracker] [bug #55059] [octave forge] (image) Failing unit test for grayslice

[Hartmut]

Follow-up Comment #13, bug #55059 (project octave):

I've just realised that my (Matlab) test results in comment #9 are not what I
wanted to test. Their calls probably fall into the syntax "grayslice(I, n)",
generating n slices.

Here is a new test code, that makes sure that the syntax "grayslice(I, v)" is
called with a vector v:


klassen = {'uint8', 'uint16', 'int16', 'single', 'double'};
for num = 1:length(klassen)
    disp('----------');
    klasse = klassen{num}
    if any(strcmp(klasse, {'uint8', 'int8', 'uint16', 'int16'}))
        vec = [intmin(klasse): intmax(klasse)];
    else
        vec = [0:0.001:1];
        cast(vec, klasse);
    end
    min_max = [min(vec), max(vec)]
    
    erg0506 = grayslice(vec, [0.5 0.6]);
    first1_ind = find(erg0506);
    first1_erg0506 = vec(first1_ind(1))
    
    erg56 = grayslice(vec, [5 6]);
    first1_ind = find(erg56);
    first1_erg56 = vec(first1_ind(1))
    
    int56 = uint8([5 6]);
    ergint56 = grayslice(vec, int56);
    first1_ind = find(ergint56);
    first1_ergint56 = vec(first1_ind(1))
end


And here are the corresponding Matlab results:

 ----------
 klasse =
     'uint8'
 min_max =
   1x2 uint8 row vector
      0   255
 first1_erg0506 =
   uint8
    1
 first1_erg56 =
   uint8
    5
 first1_ergint56 =
   uint8
    5
 ----------
 klasse =
     'uint16'
 min_max =
   1x2 uint16 row vector
        0   65535
 first1_erg0506 =
   uint16
    1
 first1_erg56 =
   uint16
    5
 first1_ergint56 =
   uint16
    5
 ----------
 klasse =
     'int16'
 min_max =
   1x2 int16 row vector
    -32768    32767
 first1_erg0506 =
   int16
    -32767
 first1_erg56 =
   int16
    -32763
 first1_ergint56 =
   int16
    -32763
 ----------
 klasse =
     'single'
 min_max =
      0     1
 first1_erg0506 =
     0.5000
 first1_erg56 =
      1
 first1_ergint56 =
      1
 ----------
 klasse =
     'double'
 min_max =
      0     1
 first1_erg0506 =
     0.5000
 first1_erg56 =
      1
 first1_ergint56 =
      1


Those outputs are different from the results in comment #9. 

My implications from this are:
* giving v=[5 6] does the same, it does not matter if v is double or uint8. I
suspect that the CLASS OF V does not matter at all.
* giving v=[5 6] on an IMAGE I of a INTEGER class, does the first "cut" at the
5th smalles value that is possible in the (integer class) of I. I suspect that
for those integer images, the vector v is taken relative to intmin of the
image.
* giving v=[5 6] on an IMAGE I of FLOAT class, does the cut at the value of 1
(probably float inputs are expected to be between 0 and 1, and that's why 5 is
kind of Inf in this case). I suspect that for float images, the vector v is
cast to a float class (and maybe afterwards trunctated to the interval 0..1)

Does this make sense? Any thoughts?

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