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

[Hartmut]

Follow-up Comment #7, bug #51769 (project octave):

@Christof: 
* Regarding your argumentation about rounding issues: I would also prefer to
use the path (1.), i.e. keeping the scale factor untouched and slightly
increase the output image pixel number if necessary. If you have checked
(without looking at the Matlab source code) that this is also the Matlab
behavior, then this path is definitly even better, because it is more Matlab
compatible (and still correct in some sense). Image analysis (like done with
Octave's image package) might differ here from image edition (like done with
Gimp).
* Regarding your second patch: I think it doesn't make a difference if you
prepare a new patch based on your old patch, or based on the image package
repo version. It is good that you are already presenting your patches in a
separate (bitbucket) repository, which is the preferred way of Carne to review
patches (if I understood him right).
* The philosophy about tests in the image package is to have the test results
Matlab compatible (if somehow possible). If there is a (intentional or also
unwanted) Matlab incompatibility, then it's good to leave a failing (!) test
in place, to document this behavior. So please do not change existing test,
just because they are failing, please only change tests if those tests weren't
Matlab compatible and your improved function now is. You can always add new
tests, if you want to.

Eventually we need to wait for Carne's comments and review, here. He is not
only the package maintainer of the image package, but he is also the latest
author of the current imresize.m function and its current indexing approach.

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