Bug 338506

Summary: image wallpapers are blurry in scaled and scaled and cropped mode
Product: [Plasma] plasmashell Reporter: jhnnslschnr
Component: Image WallpaperAssignee: Marco Martin <notmart>
Status: RESOLVED UPSTREAM    
Severity: normal CC: abhinav.kumar.in, account-kde, aleixpol, bugs.kde, chgonzalezg, dpross1100, Flupp+bugs.kde.org, godlike64, hotmusicfan, jeremy9856, k3rnelj, kam1kaz3, kde, kde, kingsamses+kde, matt.ruffalo, n.schnelle, nitrosito, sine.nomine, sonichedgehog_hyperblast00, stephane.treboux, tuukka.verho, vamp898
Priority: NOR    
Version: master   
Target Milestone: 1.0   
Platform: Arch Linux   
OS: Linux   
Latest Commit: Version Fixed In:
Sentry Crash Report:
Attachments: test image with sharp edged text and high resolution
Screenshot of the test wallpaper in scaled and cropped mode after editing the main.qml
Screenshot of the test wallpaper in scaled and cropped mode after applying the patch from Thomas Wucher
original main.qml from plasma 5.3.2
original main.qml from plasma 5.3.2
Issue still happening on rotated screens after patching main.qml
Wallpaper to verify what should actually be shown
Patch for main.qml to keep the aspect ratio
Closeup of a non-rotated screen in the comment #28 screenshot, showing a grid-like pattern
A picture with a large width and a small height.
A picture with a small width and a large height.
attachment-18480-0.html

Description jhnnslschnr 2014-08-23 19:26:31 UTC
Image wallpapers are displayed blurry when using scaled or scaled and cropped mode.
The amount of blur is quite small, so it is not the blur effect accidently applied on the wallpaper, but propably a rendering problem.
Comment 1 Vamp898 2014-08-24 15:49:59 UTC
Its defenetly to the down-scaling.

A lot of my Wallpapers have a native Resolution of my digital Camera (46 Megapixels), if i choose them as wallpaper, its like taking of my glasses.

I can confirm that this does not happen with Plasma 4 or GNOME 3 or Windows or any other DE on this planet, would be nice if this is _not_ a feature ;)
Comment 2 David Edmundson 2014-08-26 14:29:32 UTC
Please attach a wallpaper that goes wrong when scaling.
Comment 3 jhnnslschnr 2014-08-26 15:18:21 UTC
Created attachment 88437 [details]
test image with sharp edged text and high resolution
Comment 4 David Edmundson 2014-08-26 15:22:51 UTC
Heh, nice idea.
Thanks.
Comment 5 David Edmundson 2014-08-26 15:40:18 UTC
I see why.

When we load the image, as well as scaling the image (which is all trilinear and smooth and lovely) we also set a sourceSize. 

This sourceSize determines how big the original texture we load is, which is done by the QImageLoader, which is clearly not quite as smooth.

It's rather important as otherwise we end up keeping a monsterous uncompressed image in both heap and GPU memory. I don't want to see that reverted as that just gives us a different problem.

If you can, could you find /usr/share/plasma/wallpapers/org.kde.image/contents/ui/main.qml and remove the lines 

        sourceSize {
            width: imageA.width
            height: imageA.height
        }

(and the same for imageB) and see if that makes a difference.

We may need to go back to making wallpapers go via the old cpp wallpaper loading.
Comment 6 jhnnslschnr 2014-08-26 16:43:35 UTC
Created attachment 88439 [details]
Screenshot of the test wallpaper in scaled and cropped mode after editing the main.qml

Editing main.qml did change it, now it does not get blurred anymore, but it is still strange: There are grey pixels, meaning it gets interpolated in some way, but most parts are very edgy. In KDE 4 the wallpaper is shown more smoothly.
Comment 7 Matt Ruffalo 2015-04-07 15:17:39 UTC
This still occurs in the current state of Kubuntu 15.04 -- I don't imagine it'll help much to attach more images, but it's easy to reproduce.
Comment 8 Flupp 2015-05-15 11:05:01 UTC
#347610 seems to be a duplicate
Comment 9 Thomas Wucher 2015-06-13 15:46:50 UTC
I'm also affected by this bug. How to reproduce:

1. Choose high-res image with contrasty sharp edges
2. Set as wallpaper
3. It looks blurry as hell
4. Scale the image with gimp to native screen resolution
5. Set scaled image as wallpaper and it looks a lot better

Scaling the image is not a real option for me, as i often use external displays with different resolutions, so i would have to switch to a differently scaled wallpaper everytime i attach a different screen to my laptop.
Comment 10 Stéphane Tréboux 2015-06-22 16:30:23 UTC
I'm also affected by this bug.
Comment 11 Bhushan Shah 2015-06-25 13:18:53 UTC
*** Bug 349591 has been marked as a duplicate of this bug. ***
Comment 12 Martin Kyral 2015-07-02 12:48:45 UTC
(In reply to David Edmundson from comment #5)
> I see why.
> 
> When we load the image, as well as scaling the image (which is all trilinear
> and smooth and lovely) we also set a sourceSize. 
> 
> This sourceSize determines how big the original texture we load is, which is
> done by the QImageLoader, which is clearly not quite as smooth.
> 
> It's rather important as otherwise we end up keeping a monsterous
> uncompressed image in both heap and GPU memory. I don't want to see that
> reverted as that just gives us a different problem.
> 
> If you can, could you find
> /usr/share/plasma/wallpapers/org.kde.image/contents/ui/main.qml and remove
> the lines 
> 
>         sourceSize {
>             width: imageA.width
>             height: imageA.height
>         }
> 
> (and the same for imageB) and see if that makes a difference.
> 
> We may need to go back to making wallpapers go via the old cpp wallpaper
> loading.

Is there another way to workaround this annoyance? I don;t have these lines in /usr/share/plasma/wallpapers/org.kde.image/contents/ui/main.qml anymore, but the wallpapers are still blurry and thus ugly.
Comment 13 Kornel Jankowski 2015-07-27 21:27:18 UTC
Maybe, since it doesn't look like anyone has the intention of fixing the bug, maybe a currently valid workaround could be described? This really makes the KDE desktop, which had been beautiful for years, look like a nightmare.
Comment 14 Stéphane Tréboux 2015-07-28 06:50:55 UTC
The workaround is really easy: you just need to do like you did in the late 1990 with Windows 95 and 98. Put a Ace of Base album and some AA-batteries in your portable CD player and put one of your neon shirts on. Then open your preferred image editor like Krita, Deluxe Paint or Gimp. I like Krita because it has a direct menu to resize an image (http://www.davidrevoy.com/data/images/blog/2013/09/gettingstarted3/tutorial-getting-started-krita_part3_03.tb.jpg). Then resize to your screen resolution, save, use as your wallpaper and drink a Crystal Pepsi to refresh yourself after this hard work :-)
Comment 15 Kornel Jankowski 2015-07-28 06:56:59 UTC
(In reply to Stéphane Tréboux from comment #14)
> The workaround is really easy: you just need to do like you did in the late
> 1990 with Windows 95 and 98. Put a Ace of Base album and some AA-batteries
> in your portable CD player and put one of your neon shirts on. Then open
> your preferred image editor like Krita, Deluxe Paint or Gimp. I like Krita
> because it has a direct menu to resize an image
> (http://www.davidrevoy.com/data/images/blog/2013/09/gettingstarted3/tutorial-
> getting-started-krita_part3_03.tb.jpg). Then resize to your screen
> resolution, save, use as your wallpaper and drink a Crystal Pepsi to refresh
> yourself after this hard work :-)

No, I will not keep separate copies of the ~thousand pictures I use in the wallpaper slideshow and i will not readjust the settings when I change a monitor (which I do many times a day). I'd recommend thinking of other-than-yourself cases before you make fun of someone.
Comment 16 Stéphane Tréboux 2015-07-28 07:27:52 UTC
HI Kornel,

You didn't mentioned you are using a sideshow with different monitors; since l don't live inside your computer I couldn't guess. And the humor is not about a person in particular, it's about Plasma not implementing correctly a feature which is standard since Windows XP.

I have no idea on how to fix the root issue in Plasma.
If you want to consider resizing your (many) pictures here are a few pointers.
This will return the current monitor resolution:
xrandr | grep \* | awk '{print $1}'
Then this resolution can be used as a parameter for the "convert" tool (based on ImageMagick).
And this even works without wearing a neon shirt :-)

Have a nice week!
Comment 17 Kornel Jankowski 2015-07-28 17:35:35 UTC
(In reply to Stéphane Tréboux from comment #16)
> HI Kornel,
> 
> You didn't mentioned you are using a sideshow with different monitors; since
> l don't live inside your computer I couldn't guess. And the humor is not
> about a person in particular, it's about Plasma not implementing correctly a
> feature which is standard since Windows XP.
> 
> I have no idea on how to fix the root issue in Plasma.
> If you want to consider resizing your (many) pictures here are a few
> pointers.
> This will return the current monitor resolution:
> xrandr | grep \* | awk '{print $1}'
> Then this resolution can be used as a parameter for the "convert" tool
> (based on ImageMagick).
> And this even works without wearing a neon shirt :-)
> 
> Have a nice week!

Sorry for the overreaction, but as much as I loved plasma4 and all od KDE4, I now am forced to be angry with the newer versions. Just too many places where things went wrong and it's on the verge of usability..
Comment 18 Thomas Wucher 2015-07-30 20:49:06 UTC
Possible workaround:

Delete all lines assigning currentImage.sourceSize from /usr/share/plasma/wallpapers/org.kde.image/contents/ui/main.qml

Heres a patch: http://pastebin.com/XcUw4wpr
Comment 19 jhnnslschnr 2015-07-30 21:09:50 UTC
Created attachment 93803 [details]
Screenshot of the test wallpaper in scaled and cropped mode after applying the patch from Thomas Wucher

This patch works for me (tested with scaled and scaled and cropped). A screenshot of the result is attached, it looks ok for me.
Comment 20 Martin Kyral 2015-07-30 21:17:11 UTC
(In reply to Thomas Wucher from comment #18)
> Possible workaround:
> 
> Delete all lines assigning currentImage.sourceSize from
> /usr/share/plasma/wallpapers/org.kde.image/contents/ui/main.qml
> 
> Heres a patch: http://pastebin.com/XcUw4wpr

You're the king! :) This ain't workaround, this is the fix. Developers, please include this patch.. It fixes something that is simply broken. And I don't mean "just" the blurriness - I mean also other scaling modes which provided weird results. Thanks!
Comment 21 David Edmundson 2015-07-30 23:44:47 UTC
This is a workaround please see comment 5
Comment 22 Thomas Wucher 2015-07-31 07:38:23 UTC
David is right, my patch is definitely just a workaraound. I recommend to scale your images with your favourite image editing tool to fit the largest resolution you are usually using. Scaling down to smaller screen works well when my patch is applied and you don't waste a lot of memory, so this should be a good compromise.
Comment 23 jhnnslschnr 2015-07-31 09:32:27 UTC
(In reply to jhnnslschnr from comment #6)

I dont know why i found that strange, the fix from comment #5 had pretty much the same result as the patch (compare the screenshots). However i cant find those lines in main.qml anymore.
Comment 24 Kornel Jankowski 2015-07-31 17:49:46 UTC
In my case applying this results, unfortunately, in getting a black screen instead of any kind of wallpaper.
 //Could somebody please post the original file somewhere if they have it somewhere handy? The response to this was so enthusiastic that I lost the originals while patching..
Comment 25 jhnnslschnr 2015-07-31 17:53:34 UTC
Created attachment 93818 [details]
original main.qml from plasma 5.3.2
Comment 26 jhnnslschnr 2015-07-31 17:55:07 UTC
Created attachment 93819 [details]
original main.qml from plasma 5.3.2

Sorry, was the modified, now corrected.
Comment 27 godlike 2015-11-11 12:48:00 UTC
This issue still happens to me after patching main.qml. It of course only happens when the resolution of the wallpaper does not match the resolution of the screen, and might be exacerbated by the fact that the screens where this is currently happening to me are 90°-rotated screens. I'm attaching a screenshot of my desktop and the wallpaper I'm using so you can see what i mean. If I had not ditched KDE 4 I would be able to take a screenshot of the same desk under KDE 4 ;)
Comment 28 godlike 2015-11-11 12:49:09 UTC
Created attachment 95438 [details]
Issue still happening on rotated screens after patching main.qml
Comment 29 godlike 2015-11-11 12:52:16 UTC
Created attachment 95439 [details]
Wallpaper to verify what should actually be shown

Had to downgrade the quality a bit or I would go over the limit. Original file is in https://interfacelift.com/wallpaper/details/3162/christmas_eve_in_seattle.html with a 3840x2400 resolution
Comment 30 jeremy9856 2015-11-29 10:17:06 UTC
That really should be fixed now. It's a really really basic feature and make KDE look like half backed whereas it's not. Look at the difference between KDE and Gnome :

KDE http://bit.ly/1lnG2Oh
Gnome http://bit.ly/1lnG5tA

https://forum.manjaro.org/index.php?topic=28705.0
Comment 31 jeremy9856 2015-12-10 10:50:14 UTC
A little reminder.
Comment 32 Matt Ruffalo 2015-12-11 19:08:30 UTC
I realize that the normal mode of operation for open source software is "feel free to fix it yourself if the project's normal contributors aren't responding as fast as you would like", but this bug seems to require some expert knowledge to fix without introducing the issues that David Edmundson described in comment #5.

This bug is still present in Kubuntu 15.10 (Plasma 5.4.2 I think) and the current unfinished state of what will be Kubuntu 16.04 LTS (a mix between Plasma 5.4.3 and 5.5 as far as I can tell). I agree with others in that this makes the Plasma 5 desktop look unfinished and unpolished; it makes me think "if this important functionality is broken in Plasma 5 (despite it being a solved problem for a long time, and working perfectly in every other contemporary operating system and desktop environment), I wonder what else is broken. Maybe I'd rather not find out the hard way, and stick with KDE 4 for now."

This bug was filed against Arch's packages, but I think it's reasonable to say that many users will first experience Plasma 5 by using/trying Kubuntu 16.04 LTS, and it would be really nice if this could be fixed in whatever Plasma version (5.6?) ships with that distribution.
Comment 33 jeremy9856 2015-12-12 13:50:36 UTC
> "if this important functionality is broken in Plasma 5 (despite it being a solved problem for a long time, and working perfectly in every other contemporary operating system and desktop environment), I wonder what else is broken."

I agree with this feeling but I think it's not fair. A lot of work has been, and is being made in Plasma 5, KF5 and KDE apps.
Comment 34 Kornel Jankowski 2015-12-12 20:31:16 UTC
I think Mr. Ruffalo's main point was how badly that makes KDEPlasma look, even though we know how much work was put into it. 

And he is right, because an average user won't look at the bug tracker to see if someone's attending such an issue, but just say "Ugh, this is ugly, give me my windows back." - And they would be right, because a wallpaper is a really basic UX thing, it shouldn't be rocket science in a DE like this.

It is hard for an average user to understand what kind and how much work was put into KDE, and they won't even try if their wallpaper will look as they spilled something on it.

And this is one of a few reasons (there were a few other similar unsolved issues like this) I myself got back to using KDE4. How does thinking how beautiful an engine runs things help me, when I can't connect a monitor without crashing Plasma and my wallpaper is blurred to a point where I start checking if my glasses are still alright?

And it's, i think, a valuable point to make here, what Mr. was also trying to put through, if I got him right, is that maybe there should be some better prioritization of work:  For it's really hard to appreciate a car when it has an ugly, rusty body that puts everyone off, even if the insides are Ferrari. Especially when it seems that this little paint job shouldn't be such a great strain to someone who knows the proper KDE insides.
Comment 35 jeremy9856 2015-12-15 13:24:58 UTC
> (In reply to David Edmundson from comment #5)
> This sourceSize determines how big the original texture we load is, which is
> done by the QImageLoader, which is clearly not quite as smooth.

Is it planned to fix QImageLoader ? That seem to be the right way to fix this don't you think ?
Comment 36 jeremy9856 2016-01-02 16:10:19 UTC
Should we understand that nothing is planned ?
Comment 37 jeremy9856 2016-01-22 13:58:19 UTC
That's disappointing
Comment 38 Carlos 2016-01-26 00:51:36 UTC
Same problem here
Comment 39 dpross1100 2016-01-29 19:44:38 UTC
I think this bug should get a higher priority, just because you can tell that a lot of work went into making Plasma 5 beautiful, and this bug spoils it.  I am okay with working around it by saving cropped versions of my photos and using the centered wallpaper mode, but the average user isn't going to know what the problem is or how to work around it.  They'll just get frustrated and switch to something else, which would be a shame.  

I'm looking forward to this getting fixed soon (fingers crossed).
Comment 40 jhnnslschnr 2016-01-29 22:58:08 UTC
(In reply to David Edmundson from comment #5)
> This sourceSize determines how big the original texture we load is, which is
> done by the QImageLoader, which is clearly not quite as smooth.
> 
> It's rather important as otherwise we end up keeping a monsterous
> uncompressed image in both heap and GPU memory. I don't want to see that
> reverted as that just gives us a different problem.

Is there no way to load the image from file, smoothly downscale it to the currently needed resolution(s), and only save this result(s) in heap and GPU memory?
Comment 41 jeremy9856 2016-02-19 09:47:24 UTC
Is there a fix planned ?
Comment 42 Kai Uwe Broulik 2016-03-08 11:23:35 UTC
*** Bug 349392 has been marked as a duplicate of this bug. ***
Comment 43 Mircea Kitsune 2016-04-01 18:27:01 UTC
I can confirm this problem and am also affected by it: I use Slideshow as my wallpaper type, with Scaled and Cropped for positioning. Some high resolution wallpapers (not all, appears to be random) appear blurry and pixelated. Opening the same image in Gwenview and zooming to the exact same size looks fine however. This did not exist in KDE4, and started happening with Plasma 5. Very annoying bug... please try to find a fix for this!
Comment 44 jeremy9856 2016-08-20 20:28:52 UTC
I'm thinking using KDE again but will this be fixed ?
Thanks !
Comment 45 jeremy9856 2016-08-27 12:02:51 UTC
I know that the devs are very very busy but since nothing seems to be done for 2 years about this bug I opened an issue against Qt. I don't know if it's the right thing to do, but at least I try to do something.

https://bugreports.qt.io/browse/QTBUG-55571
Comment 46 jeremy9856 2016-09-11 18:35:07 UTC
Good news ! The bug is under investigations in Qt. 

https://bugreports.qt.io/browse/QTBUG-55571
Comment 47 hotmusicfan 2016-12-08 15:06:14 UTC
Still existing in Plasma 5.8.3.
Comment 48 Mircea Kitsune 2016-12-08 15:38:18 UTC
This issue is still an annoyance in Plasma 5.8.4, KDE Frameworks 5.28.0, QT 5.7.0. I really hope we will be seeing it fixed, it's messing up a lot of high-resolution wallpapers.
Comment 49 Tuukka Verho 2016-12-14 10:25:56 UTC
I found the problem and a fix!

Setting sourceImage.size to the size of the screen may change the aspect ratio of the image. Qt handles this especially badly and I think there is a bug in Qt regarding that. However, there is no reason to change the aspect ratio back and forth. It's better to set just the width or the height of the source and let Qt keep the aspect ratio.

Changing all occurrences of the line

currentImage.sourceSize = Qt.size(root.width, root.height)

in /usr/share/plasma/wallpapers/org.kde.image/contents/ui/main.qml to

currentImage.sourceSize.width = root.width

fixes it for me. I think this is an actual fix, not just a workaround.
Comment 50 Tuukka Verho 2016-12-14 10:27:12 UTC
Created attachment 102776 [details]
Patch for main.qml to keep the aspect ratio
Comment 51 Tuukka Verho 2016-12-14 10:35:01 UTC
Actually the correct solution would involve figuring out whether sourceSize.width or sourceSize.height should be set (depends on the relative aspect ratios of the screen and the wallpaper image). But this patch should serve as a decent workaround as long as the aspect ratios are not vastly different.
Comment 52 hotmusicfan 2016-12-14 11:44:10 UTC
(In reply to Tuukka Verho from comment #49)
> I found the problem and a fix!
> 
> Setting sourceImage.size to the size of the screen may change the aspect
> ratio of the image. Qt handles this especially badly and I think there is a
> bug in Qt regarding that. However, there is no reason to change the aspect
> ratio back and forth. It's better to set just the width or the height of the
> source and let Qt keep the aspect ratio.
> 
> Changing all occurrences of the line
> 
> currentImage.sourceSize = Qt.size(root.width, root.height)
> 
> in /usr/share/plasma/wallpapers/org.kde.image/contents/ui/main.qml to
> 
> currentImage.sourceSize.width = root.width
> 
> fixes it for me. I think this is an actual fix, not just a workaround.

It is exactly workaround, the user cannot change these values for every single image he/she uses.
Comment 53 Mircea Kitsune 2016-12-14 12:39:50 UTC
(In reply to Tuukka Verho from comment #49)

Thank you very much for the fix, I hope it will be in soon! I hope this doesn't mean QT is currently rescaling the image with some builtin image processing tool, which IMO would be silly and absolutely unnecessary: It should simply display the image at a size that fits the screen, resizing it just like a web browser resizes an embedded image to make it fit a HTML element. I thought this is what it was doing all along...
Comment 54 Tuukka Verho 2016-12-14 14:31:14 UTC
(In reply to Tuukka Verho from comment #49)

> Setting sourceImage.size to the size of the screen may change the aspect
> ratio of the image. Qt handles this especially badly and I think there is a
> bug in Qt regarding that. However, there is no reason to change the aspect
> ratio back and forth. It's better to set just the width or the height of the
> source and let Qt keep the aspect ratio.

Actually the Qt documentation says the aspect ratio will be maintained regardless of what the sourceSize is. So the patch should not be needed and this must be a Qt bug, somehow Qt manages to mess up the scaling in some cases when using sourceSize. I have submitted a report: https://bugreports.qt.io/browse/QTBUG-57619
Comment 55 Tuukka Verho 2016-12-14 14:38:23 UTC
(In reply to Mircea Kitsune from comment #53)
> (In reply to Tuukka Verho from comment #49)
> 
> Thank you very much for the fix, I hope it will be in soon! I hope this
> doesn't mean QT is currently rescaling the image with some builtin image
> processing tool, which IMO would be silly and absolutely unnecessary: It
> should simply display the image at a size that fits the screen, resizing it
> just like a web browser resizes an embedded image to make it fit a HTML
> element. I thought this is what it was doing all along...

Well, it has to load the image to memory before drawing it to the screen. The question is, in which size it should load it? If you can assume the display size of the image stays constant (like in the case of a wallpaper), it makes sense to save it at the same size as it is shown. However, Qt Quick was designed for dynamic interfaces without such assumptions, so you have to tell it the size you want to store it.
Comment 56 godlike 2016-12-14 15:07:53 UTC
(In reply to Tuukka Verho from comment #51)
> But this patch should serve as a decent workaround as long as the aspect ratios are not vastly different.

Indeed. If a screen is rotated (like in my previous example) the issue still occurs after patching main.qml in this alternative way unfortunately.
Comment 57 Tuukka Verho 2016-12-14 15:52:32 UTC
(In reply to godlike from comment #56)
> Indeed. If a screen is rotated (like in my previous example) the issue still
> occurs after patching main.qml in this alternative way unfortunately.

It's a bit strange that you have the bug even after applying the patch from comment #20. I can see the bug in both your rotated and non-rotated screens. Could you make sure you have removed or commented out all occurrences of the line

currentImage.sourceSize = Qt.size(root.width, root.height)

in your main.qml? If you make any changes, log out and log in again.
Comment 58 godlike 2016-12-15 14:34:54 UTC
(In reply to Tuukka Verho from comment #57)
> (In reply to godlike from comment #56)
> > Indeed. If a screen is rotated (like in my previous example) the issue still
> > occurs after patching main.qml in this alternative way unfortunately.
> 
> It's a bit strange that you have the bug even after applying the patch from
> comment #20. I can see the bug in both your rotated and non-rotated screens.
> Could you make sure you have removed or commented out all occurrences of the
> line
> 
> currentImage.sourceSize = Qt.size(root.width, root.height)
> 
> in your main.qml? If you make any changes, log out and log in again.

I was reloading plasma shell but for the sake of testing I logged out and back in. Neither with:

currentImage.sourceSize.width = root.width

nor with those lines commented can I get a good rendering of the wallpaper on my rotated screen. Were you able to temporarily rotate a screen and get a nice looking wallpaper on it?

BTW I'm currently at plasma-5.8.3 with QT 5.7
Comment 59 Tuukka Verho 2016-12-15 19:31:28 UTC
(In reply to godlike from comment #58)
> (In reply to Tuukka Verho from comment #57)
> > (In reply to godlike from comment #56)
> > > Indeed. If a screen is rotated (like in my previous example) the issue still
> > > occurs after patching main.qml in this alternative way unfortunately.
> > 
> > It's a bit strange that you have the bug even after applying the patch from
> > comment #20. I can see the bug in both your rotated and non-rotated screens.
> > Could you make sure you have removed or commented out all occurrences of the
> > line
> > 
> > currentImage.sourceSize = Qt.size(root.width, root.height)
> > 
> > in your main.qml? If you make any changes, log out and log in again.
> 
> I was reloading plasma shell but for the sake of testing I logged out and
> back in. Neither with:
> 
> currentImage.sourceSize.width = root.width
> 
> nor with those lines commented can I get a good rendering of the wallpaper
> on my rotated screen. Were you able to temporarily rotate a screen and get a
> nice looking wallpaper on it?
> 
> BTW I'm currently at plasma-5.8.3 with QT 5.7

I rotated the wallpaper (instead of monitor) and it looked good. I can see that grid-like pattern in both your landscape and rotated screens in your screenshot in comment #28. I only get that pattern when sourceSize is being used. Also the rotated images are very blurry, that would be expected when you use sourceSize.
Comment 60 Tuukka Verho 2016-12-15 19:32:54 UTC
Created attachment 102799 [details]
Closeup of a non-rotated screen in the comment #28 screenshot, showing a grid-like pattern
Comment 61 Tuukka Verho 2016-12-15 19:42:24 UTC
godlike: the following minimal test should show whether you have the bug even without sourceSize. You need to install qmlscene, and save the following code into test.qml. Put the wallpaper to the same directory (adjust the filename if necessary) and then run with "qmlscene test.qml". It should show a very obvious grid-like pattern (at least if you take a screenshot and zoom in). Then you can try commenting out the sourceSize line to see whether that gets rid of the pattern of not.

test.qml:

import QtQuick 2.5
Image {
	width: 900 
	height: 600
	source: "03162_christmaseveinseattle_3840x2400.jpg"
	sourceSize: Qt.size(width, height) // try commenting this out
}
Comment 62 Abhinav Kumar 2017-04-11 12:46:42 UTC
The associated Qt bugfix has been merged into the dev (Qt 5.9) branch.
Comment 63 jeremy9856 2017-08-09 17:16:47 UTC
This bug can be closed now it seem ?

https://bugreports.qt.io/browse/QTBUG-55571
Comment 64 godlike 2017-08-09 19:29:56 UTC
(In reply to Tuukka Verho from comment #61)
> godlike: the following minimal test should show whether you have the bug
> even without sourceSize. You need to install qmlscene, and save the
> following code into test.qml. Put the wallpaper to the same directory
> (adjust the filename if necessary) and then run with "qmlscene test.qml". It
> should show a very obvious grid-like pattern (at least if you take a
> screenshot and zoom in). Then you can try commenting out the sourceSize line
> to see whether that gets rid of the pattern of not.
> 
> test.qml:
> 
> import QtQuick 2.5
> Image {
> 	width: 900 
> 	height: 600
> 	source: "03162_christmaseveinseattle_3840x2400.jpg"
> 	sourceSize: Qt.size(width, height) // try commenting this out
> }

Sorry for the (HUGE) delay. I can clearly see a difference between commenting and uncommenting. With sourceSize commented, the image look much crisper (less blurriness).

Does this mean that something must be updated? As I've said before, all appearances of sourceSize have been commented in my /usr/share/plasma/wallpapers/org.kde.image/contents/ui/main.qml but the issue still persists. Should I update to qt-5.9 once it's released?
Comment 65 Dmitrii Chermnykh 2017-08-10 07:54:32 UTC
> This bug can be closed now it seem ?

This bug hasn't been reproduced since I've updated to QT 5.9
Comment 66 Kai Uwe Broulik 2017-08-10 08:30:34 UTC
See also https://bugreports.qt.io/browse/QTBUG-57619
Comment 67 Flupp 2017-08-23 15:05:47 UTC
Created attachment 107483 [details]
A picture with a large width and a small height.

Currently I am using the Arch Linux x86_64 package plasma-workspace version 5.10.4-2.

With this version, I cannot reproduce the problem, if the “Positioning” option is set to “Scaled and Cropped”.

Unfortunately, now there is blurring, if the “Positioning” option is set to “Scaled”. I attached two svg pictures that show the problem very clearly. The problem seems to occur, when the aspect ration of the picture deviates significantly from the aspect ration of the screen.

Also I noticed that plasmashell occasionally segfaults when changing the “Positioning” option between “Scaled” and “Scaled and Cropped” and applying the change afterwards. (Maybe this is worth a separate bug report.)
Comment 68 Flupp 2017-08-23 15:06:28 UTC
Created attachment 107484 [details]
A picture with a small width and a large height.
Comment 69 godlike 2017-08-24 02:51:11 UTC
Updated to qt-5.9.1 today (and frameworks-5.37, plasma-5.10, apps-17.08 in the process) and I am no longer hitting the blurry issue. The sourceSize lines in main.qml are there (due to the update) but the issue is not present. Does this mean this was a QT bug all along?
Comment 70 Nikola Schnelle 2017-08-24 04:20:32 UTC
Created attachment 107492 [details]
attachment-18480-0.html

yes

On Thu, Aug 24, 2017 at 4:51 AM, godlike <bugzilla_noreply@kde.org> wrote:

> https://bugs.kde.org/show_bug.cgi?id=338506
>
> --- Comment #69 from godlike <godlike64@gmail.com> ---
> Updated to qt-5.9.1 today (and frameworks-5.37, plasma-5.10, apps-17.08 in
> the
> process) and I am no longer hitting the blurry issue. The sourceSize lines
> in
> main.qml are there (due to the update) but the issue is not present. Does
> this
> mean this was a QT bug all along?
>
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