[Octave-bug-tracker] [bug #47516] image package: mat2gray rounding errorrs when rescaling

[Avinoam Kalma]

Follow-up Comment #2, bug #47516 (project octave):

The Anonymous is right, the value in place of the original minimum is 1
instead of 0.

The problem is with the lines:


  in(in <= out_min) = 0;
  in(in >= out_max) = 1;


The value at the minimum is changed to 0, and since 0 is greater
than the original maximum, it changed again to 1. It will happen
in any negative matrix. The solution is:


  idx_max = (in >= out_max);
  in(in <= out_min) = 0;
  in(idx_max) = 1;
 

and a simple test will check this situation:


%!assert(mat2gray([-3 -2 -1]), [0 0.5 1]);


before this fix the result is [1 0.5 1]

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