[Octave-bug-tracker] [bug #51769] [octave forge] (image) imresize bilinear interpolation inaccurate

[Christof Kaufmann]

URL:
  <http://savannah.gnu.org/bugs/?51769>

                 Summary: [octave forge] (image) imresize bilinear
interpolation inaccurate
                 Project: GNU Octave
            Submitted by: christofkaufmann
            Submitted on: Wed 16 Aug 2017 09:01:37 PM UTC
                Category: Octave Forge Package
                Severity: 3 - Normal
                Priority: 5 - Normal
              Item Group: Inaccurate Result
                  Status: None
             Assigned to: None
         Originator Name: 
        Originator Email: 
             Open/Closed: Open
         Discussion Lock: Any
                 Release: 4.0.3
        Operating System: Any

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Details:

octave-image version 6.2.1 (default branch from repository)

Hi,

I noticed very inaccurate results when using the 'bilinear' method with
imresize. I can give a small example:

in = checkerboard (1, [2 2]);
imresize (in, 0.5, 'bilinear')
## gives:
## ans =  0.0   0.7
##        1.0   0.0

The expected behaviour would be (which matlab would give for a larger
example):

imresize (in, 0.5, 'bilinear')
## gives:
## ans = 0.50   0.35
##       0.50   0.35






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