[Octave-bug-tracker] [bug #45088] image package: rangefilt requires domain and image to have equal number of dimensions

[Hartmut]

Follow-up Comment #21, bug #45088 (project octave):

The Matlab result for the rangefilt command in comment #19 is the following:


    19    23    23    15     8
    20    23    23    21    14
    19    19    16    19    19
    14    21    23    23    20
     8    15    23    23    19


There are also a bunch of Matlab compatible tests for rangefilt in file #39544
(from patch #9235).

When I use the patch from comment #16 (file #39535) in rangefilt.m then I get
the following result for the rangefilt command in comment #19:


   19   23   23   15    8
   20   23   23   21   14
   19   19   16   19   19
   14   21   23   23   20
    8   15   23   23   19


This is identical to the above Matlab result. So Avinoam's latest patch (file
#39535) seems to generate Matlab compatible results even in this new test
case. (It also passes all the Matlab compatible tests from the mentioned file
#39544.)

Conclusion: No, the (patched) rangefilt.m is not completly wrong. It gives
Matlab compatible results in all 14 testcases that we currently have. (The
current version in the repo IS completely wrong, though.)

I am very open to deal with the padding issue (in order to better deal with
different numbers of dimensions) differently. I might be a clever idea to let
_spatial_filtering_ do this padding job. (But I myself wasn't eager to
implement this padding in c code.) Now that we have so many test cases
available for all filtering functions that call _spatial_filtering_ (see patch
#9235) the risk is significantly lower to unintentionally damage something in
this code.

Using

imdilate (im, domain) - imerode (im, domain)


also produces the correct result of rangefilt for the new test case in comment
#19. (I  haven't tested the results for the other 14 testcases though.) That
might be an even better way (faster?) to do a fully new implementation of
rangefilt.m. But in this case we still need to fix the calling of
_spatial_filtering_ (for entropyfilt and stdfilt) and the padding issue for 
the remaining filter functions (probably entropyfilt, stdfilt, medfilt2,
ordfilt2, maybe more).




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