option to configure resampling filter for thumbnail generation

[specterpete]

Thumbnails are currently generated with imaging using the Lanczos resampling filter. This filter is the most resource-consuming, especially on low performance devices like raspberry pi this results in slow thumbnail generation.

I suggest to add a config option to configure the resampling filter (NearestNeighbor, Box, Linear, Hermite, MitchellNetravali, CatmullRom, BSpline, Gaussian, Lanczos, Hann, Hamming, Blackman, Bartlett, Welch, Cosine) so that thumbnail generation can be optimized towards the platform used.

[midstar]

Thank you very much for you feedback. I created a new test case, TestGenerateImageThumbnailPerformance, that generates thumbnails with different resampling filters on following branch:

 feature/imaging-resampling-filter

Unfortunately I don't see much performance gain on my ROCK64 SBC nor my Windows PC (see test results below). The quality is quite similar using all the filters except "NearestNeighbor" which has really bad quality. I suggest we simply change the resampling filter from Lanczos to Box since this is the fastest filter with, in my opinion, acceptable quality.

What do you think about that?

Filter	Rock 64	Windows PC
Lanczos	2998 ms	622 ms
CatmullRom	2876 ms	641 ms
MitchellNetravali	2884 ms	632 ms
Linear	2708 ms	555 ms
Box	2647 ms	532 ms
NearestNeighbor	2548 ms	520 ms

[specterpete]

Sounds fine to me. I expected more difference. Thanks for testing it out.

[specterpete]

Accidentally closed, sry.

[specterpete]

This might also be of interest https://github.com/fawick/speedtest-resize/blob/master/README.md

[midstar]

That link was not any happy reading for me who prefer a pure golang imaging library ;-)

If we implement #11 the speed of thumbnail generation might not be that big of an issue.

[midstar]

Resampling filter was changed from Lanczos to Box in following release:

https://github.com/midstar/mediaweb/releases/tag/mediaweb-v1.0.0.132