[Octave-bug-tracker] [bug #55780] imresize with 'cubic' option is very wrong

[anonymous]

URL:
  <https://savannah.gnu.org/bugs/?55780>

                 Summary: imresize with 'cubic' option is very wrong
                 Project: GNU Octave
            Submitted by: None
            Submitted on: Mon 25 Feb 2019 05:31:06 PM UTC
                Category: Octave Forge Package
                Severity: 3 - Normal
                Priority: 5 - Normal
              Item Group: Incorrect Result
                  Status: None
             Assigned to: None
         Originator Name: Cris Luengo
        Originator Email: address@hidden
             Open/Closed: Open
         Discussion Lock: Any
                 Release: 4.4.1
        Operating System: GNU/Linux

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Details:

When upscaling an image with imresize and the 'cubic' option, the output looks
almost like a nearest neighbor interpolation, except it has smooth transitions
from patch to patch. Cubic interpolation should yield a very smooth output.

The code below illustrates the problem. This is a small image, 16x16 pixels,
being scaled 16x to 256x256 pixels.


pkg load image
a = imread('https://i.stack.imgur.com/Au3YK.png');
b = imresize(a,16,'cubic');
imshow(b)






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