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

[Hartmut]

Follow-up Comment #15, bug #55059 (project octave):

I have changed my test scripts (from comment #9 and comment #13) to properly
use input images of all possible classes.

The result in short:
* All outputs are now Matlab COMPATIBLE (using the current grayslice from the
repository), EXCEPT for input images of class INT16 (signed integer):


 im = int16([intmin('int16'):intmax('int16')]); 
 out = grayslice(im, [5 6]);  
 first1_octave = im(find(out)(1))       % currently = 5
 first1_matlab = intmin('int16') + 5    %  = -32763


Conclusion: It seems to me that our Octave version is currently referencing
signed integer values (like int16) to the zero value, but Matlab seems to
reference them to the intmin value (of -32768). @Carne: Do you have an idea
how to change our Octave version to fix this (i.e. the above test case)?

In the following I will (only) copy the full test scripts and their Matlab
results for completeness and future reference:

1. test script with a scalar "n" parameter:


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)];
        vec = cast(vec, klasse);
    else
        vec = [0:0.001:1];
        vec = cast(vec, klasse);
    end
    min_max = [min(vec), max(vec)]
    
    erg05 = grayslice(vec, [0.5]);
    first1_ind = find(erg05);
    first1_erg05 = vec(first1_ind(1))
    
    erg5 = grayslice(vec, [5]);
    first1_ind = find(erg5);
    first1_erg5 = vec(first1_ind(1))
    
    int5 = uint8(5);
    ergint5 = grayslice(vec, [int5]);
    first1_ind = find(ergint5);
    first1_ergint5 = vec(first1_ind(1))
end

disp('-------');
disp('Bonus: (uint8 0..100)');
vec = uint8([0:100]);
erg5 = grayslice(vec, 5);
first1_ind = find(erg5);
first1_erg5 = vec(first1_ind(1))

disp('Bonus: (double 0..100)');
vec = double(vec);
erg5 = grayslice(vec, 5);
first1_ind = find(erg5);
first1_erg5 = vec(first1_ind(1))


gives the following Matlab output:


 ----------
 klasse =
     'uint8'
 min_max =
   1x2 uint8 row vector
      0   255
 first1_erg05 =
   uint8
    1
 first1_erg5 =
   uint8
    51
 first1_ergint5 =
   uint8
    51
 ----------
 klasse =
     'uint16'
 min_max =
   1x2 uint16 row vector
        0   65535
 first1_erg05 =
   uint16
    1
 first1_erg5 =
   uint16
    13107
 first1_ergint5 =
   uint16
    13107
 ----------
 klasse =
     'int16'
 min_max =
   1x2 int16 row vector
    -32768    32767
 first1_erg05 =
   int16
    -32767
 first1_erg5 =
   int16
    -19661
 first1_ergint5 =
   int16
    -19661
 ----------
 klasse =
     'single'
 min_max =
   1x2 single row vector
      0     1
 first1_erg05 =
   single
     0.5000
 first1_erg5 =
   single
     0.2000
 first1_ergint5 =
   single
     0.2000
 ----------
 klasse =
     'double'
 min_max =
      0     1
 first1_erg05 =
     0.5000
 first1_erg5 =
     0.2000
 first1_ergint5 =
     0.2000
 -------
 Bonus: (uint8 0..100)
 first1_erg5 =
   uint8
    51
 Bonus: (double 0..100)
 first1_erg5 =
      1


2. test script with a vector "v" parameter:


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)];
        vec = cast(vec, klasse);
    else
        vec = [0:0.001:1];
        vec = 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

disp('-------');
disp('Bonus: (uint8 0..100)');
vec = uint8([0:100]);
erg5 = grayslice(vec, [5 6]);
first1_ind = find(erg5);
first1_erg5 = vec(first1_ind(1))

disp('Bonus: (double 0..100)');
vec = double(vec);
erg5 = grayslice(vec, [5 6]);
first1_ind = find(erg5);
first1_erg5 = vec(first1_ind(1))


gives the following Matlab result:


 ----------
 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 =
   1x2 single row vector
      0     1
 first1_erg0506 =
   single
     0.5000
 first1_erg56 =
   single
      1
 first1_ergint56 =
   single
      1
 ----------
 klasse =
     'double'
 min_max =
      0     1
 first1_erg0506 =
     0.5000
 first1_erg56 =
      1
 first1_ergint56 =
      1
 -------
 Bonus: (uint8 0..100)
 first1_erg5 =
   uint8
    5
 Bonus: (double 0..100)
 first1_erg5 =
      5



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