https://bugzilla.wikimedia.org/show_bug.cgi?id=67525
--- Comment #8 from Gilles Dubuc <[email protected]> --- > What sort of pictures were on the survey? What settings were used, etc? One or two control images that had no specific qualities as well as several images with a lot of edges: https://www.surveymonkey.com/s/F6CGPDJ The reason I picked images with a lot of edges is that they're generally the images that gather the most complaints when we tweak thumbnailing. The same logic and parameters as the patch were applied, with ImageMagick as the scaler. Each image shown in the survey had been through 3 to 5 chaining steps. There's no denying that there is a proven quality loss on a technical level, just by virtue of resampling, but the survey results were clear about the fact that on average the chained ones were slightly preferred. Presumably because of the extra sharpening (most chaining steps meet the criteria of the sharpening check in the code). The old code sharpens once from the original, the new code may sharpen once for each chain step. The reason why thumbs are sharpened in the first place - a common practice on large websites - is that people find sharpened thumbnails to look better even when mathematically speaking they aren't (on the contrary, more original content is getting lost). It's probably because the conserved edges help with the way we recognize shapes and detail. I.e. our brain will have an easier time compensating for the loss of detail if edges are stronger, even if artificially conserving the edges actually makes more original detail disappear. And so, with chaining the edges are conserved a bit better, which is probably why they're favored in the survey results. That's the only theory I have about the counter-intuitive results. When I ran it, I was expecting to see that the chained ones would be disfavored, in which case it would have been a balancing act between what people tolerate visually and server resources. That being said, maybe if we cranked up the sharpening value on the default code, people would prefer that to the chained thumbnails. I didn't try to run the survey another time to find out. But the goal here is to save server resources while not upsetting people, not to improve the thumbnail quality/popularity. It seems like a reasonable balance to me to launch a recipe that people don't noticeably dislike on average compared to the status quo. I don't see this change as a big risk, anyway, because if a vocal minority campaigns against it, it's easy to revert and purge the images. The B plan is to perform the same chaining but to store each bucket size as a lossless format. We'd have the same speed gains, but the vastly increased storage needs means that we can't do that while we're still storing thumbnails in Swift. -- You are receiving this mail because: You are the assignee for the bug. You are on the CC list for the bug. _______________________________________________ Wikibugs-l mailing list [email protected] https://lists.wikimedia.org/mailman/listinfo/wikibugs-l
