| Summary: | Scale Down 50% is blurry with Linear Filter | ||
|---|---|---|---|
| Product: | [Applications] krita | Reporter: | Paul Geraskin <paulgeraskin> |
| Component: | General | Assignee: | Krita Bugs <krita-bugs-null> |
| Status: | CONFIRMED --- | ||
| Severity: | minor | CC: | dimula73, griffinvalley, halla, nicholaslapointe8 |
| Priority: | NOR | ||
| Version First Reported In: | 5.2.11 | ||
| Target Milestone: | --- | ||
| Platform: | Other | ||
| OS: | Linux | ||
| Latest Commit: | Version Fixed/Implemented In: | ||
| Sentry Crash Report: | |||
| Attachments: |
PSD File to test
scaled down with 2.9.0 and 3.0.0 Difference between the two images difference difference kra file |
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Description
Paul Geraskin
2017-03-01 13:40:02 UTC
As far as I know, it's actually Gimp which is at fault here. The Gimp's bilinear filter for scaling is considered so sharp that people often recommend blurring an image before scaling it down with Gimp. So, not a bug. It's a bug 100%. Bilinear Filter is the sharpest filter against Lancoz and Box filters. You forced me to open PS. )) Here are results: http://i.imgur.com/7r2s10l.png http://i.imgur.com/pfUfpOb.png Also, if I open the attached PSD file and set Krita's viewport to 50% it will have nice sharpen result. http://i.imgur.com/bEoEj2T.png Could, you change the status, please? Ше шы куфддн ф игп It is really a bug. Bilinear should be the sharpest scaling filter. Oh, come on... If it were a bug, then it would be a bug that we have had since _2004_. And in the past 13 years, nobody would have noticed it? And that is "major"? I cannot believe that. Hi, Boud! Just check the attached screenshots. The scaled image looks extremely blurry, which it didn't use to. I have a feeling that Bicubic strategy is selected somehow. When I refactored the stuff a couple of years ago, the scaled images looked okay. So I really feel that this is some kind of regression. Right now I have a freelance job where i have to paint images and then scale them down to 50% to send them to my partner. It's major for me. Sorry. ) Right now I'm using Lancoz filter. It does the job. But Linear filter is the best to scale down to 50% with the best quality. Thanks. Created attachment 104304 [details]
scaled down with 2.9.0 and 3.0.0
I have no system where 2.8 is still working, but 2.9 and 3.0 give identical results. As is to be expected, since nobody has touched this code since 2005.
I have just googled "Box vs Linear" a bit. https://www.google.ru/search?q=box+vs+linear&newwindow=1&espv=2&biw=1920&bih=961&source=lnms&tbm=isch&sa=X&ved=0ahUKEwiPgJeg57XSAhUBECwKHbMiB7EQ_AUIBigB#newwindow=1&tbm=isch&q=box+vs+linear+filter&*&imgrc=S5KTEsiHTB1dGM: https://www.google.ru/search?q=box+vs+linear&newwindow=1&espv=2&biw=1920&bih=961&source=lnms&tbm=isch&sa=X&ved=0ahUKEwiPgJeg57XSAhUBECwKHbMiB7EQ_AUIBigB#newwindow=1&tbm=isch&q=box+vs+linear+filter&*&imgrc=uHvEJXRJx-nO_M: And from the last link above: http://i.imgur.com/hLWzQwh.png I hope this will help. (In reply to Boudewijn Rempt from comment #10) > Created attachment 104304 [details] > scaled down with 2.9.0 and 3.0.0 > > I have no system where 2.8 is still working, but 2.9 and 3.0 give identical > results. As is to be expected, since nobody has touched this code since 2005. Hi, Boud! Just loking into **your** attached images, I can clearly see that 29.png is **much** sharper and clear than 30.png. So this is a regression. I have refactored transformation algorithms around 2012 and I remember that the result was much better that this. On Sun, 5 Mar 2017, Dmitry Kazakov wrote:
> Just loking into **your** attached images, I can clearly see that 29.png is
> **much** sharper and clear than 30.png. So this is a regression.
The images are absolutely identical. If I load 29 and 30 into the same image
and set the blending mode to difference, the result is a uniform black canvas.
(In reply to Boudewijn Rempt from comment #13) > The images are absolutely identical. If I load 29 and 30 into the same image > and set the blending mode to difference, the result is a uniform black > canvas. I actually notice the same as Dmitry, with 29 being sharper. Difference gives me a mostly, but certainly not entirely, black canvas. Created attachment 104559 [details]
Difference between the two images
The difference is actually not a black canvas :) It has quite a lot of data inside.
Created attachment 104560 [details]
difference
This is how I checked the difference. I see you have three layers in your stack?
Created attachment 104561 [details]
difference kra file
Argh, now I get it. That's an adjustment layer... Well, I still don't understand what can have changed -- the imagesize plugin hasn't changed, the filters haven't changed, the filters don't use vc or eigen, which have changed. Reconfirming this bug. Krita's (bi)linear downscaling is blurred compared to what GIMP produces. |
