Which file format are you saving as? By default, png saves the transparent pixels as black, and jpg doesn't support transparency in any case.

Privately received:

"
Thank you for the mail. Yes, all images are saved in png format, 
something that can be read by any other program for later publishing. 
So, changing the background color to white has no function what so ever?"


Okay, so we're talking about PNG. If I save 

* With transparency enabled, then the png has transparent pixels if I load it again
* If I disable that checkbox, and select a different color than black, like white, and I save as PNG, I do get a PNG with the transparent pixels replaced with that background color

I've checked this with 4.2.9 and with 4.3.0. Are you using distribution packages? If so, please check whether the appimage works for you.

Created attachment 127766 [details]
attachment-26864-0.html

Hello Boudewijn,

Thank you very much for your explanation. I use both in different Linux 
versions but I mostly use the appimage 4.2.9. On macOS I even use 4.3.0. 
. It doesn't make much difference to me. Well, the whole issue came up 
since I had a strange problem with Krita I couldn't recreate. It 
probably occurs when I use the soft eraser on a 8-bit grey-scale image 
with transparent background. All my images on this project, over 300 and 
increasing are meant to be on a transparent background for the later 
page design. And in some occasions a soft grey or white shade appears on 
the saved picture which is invisible in Krita. In some earlier cases 
this shade was grey which was even more disturbing. Therefor I started 
to change the background to 'white-transparent'. I found this out in 
MacOS where the color quite childishly and typical Mac is chosen by way 
of coloring pencils. So to avoid the grey shade which appeared in some 
cases, became white... until I found out that this choice wasn't saved. 
Nonetheless sometimes the shade was grey and sometimes it was white 
(when I choose the white background transparency). This I could only see 
in either other pixel programs or in de icon in the file manager. In 
Linux I always use dark or even black themes and then those pictures 
with the 'fussy' background stick out. When I load the picture again, 
select the transparent background and delete it, then the background 
shading is gone afterwards.

This figure should have a transparent background and had it through the 
whole procedure of making but once saved, the background is white, 
transparency gone. Reloading it in Krita, the background indeed appears 
to be white and when I check the background color, Krita is telling me 
that it is black and 100% transparent. I find this a bit frustrating. 
What I doe in a case like this: I load the picture again, select the 
background and delete it. After saving the thing it is OK.

I use Krita because of the brushes. No program has these nice 'brushly' 
brushes. And I don't want to use Photoshop because everybody does and 
Adobe is a shitty company, like Corel, another shitty company.

I will continue using Krita but now, when I save the picture, I have the 
file manager open next to it to see how the picture is saved and when a 
background is visible I delete it in the picture and save it again.

Well, thanks again. Keep healthy and distant.

Best regards,

Rudolf Kahl

Op 21 -04-2020 om 11:56 schreef Boudewijn Rempt:
> https://bugs.kde.org/show_bug.cgi?id=420342
>
> --- Comment #2 from Boudewijn Rempt <boud@valdyas.org> ---
> Privately received:
>
> "
> Thank you for the mail. Yes, all images are saved in png format,
> something that can be read by any other program for later publishing.
> So, changing the background color to white has no function what so ever?"
>
>
> Okay, so we're talking about PNG. If I save
>
> * With transparency enabled, then the png has transparent pixels if I load it
> again
> * If I disable that checkbox, and select a different color than black, like
> white, and I save as PNG, I do get a PNG with the transparent pixels replaced
> with that background color
>
> I've checked this with 4.2.9 and with 4.3.0. Are you using distribution
> packages? If so, please check whether the appimage works for you.
>

Created attachment 127767 [details]
Harald_Paulsen_psd_csp_pxm_krt.png

Thanks for your comment!

Automatically switching the status of this bug to REPORTED so that the KDE team
knows that the bug is ready to get confirmed.

In the future you may also do this yourself when providing needed information.

I still don't know what exactly you are doing, and I can't reproduce
any bugs regarding transparency.

"Therefor I started to change the background to 'white-transparent'."

What do you mean by this? The transparency checkerboard of the canvas?
Your layers? Your png export?

"This figure should have a transparent background and had it through the
whole procedure of making but once saved, the background is white,
transparency gone."

You should save your images as kra files and only export them to other
file formats once you are done. If you don't export the png with "Store
alpha channel" enabled, then (and only then) you get to pick a colour
at the bottom of the export dialog with which your transparency is
going to be replaced and then, yes, the transparency will be gone in
the exported png. Even if you open that png up again in Krita.

"And in some occasions a soft grey or white shade appears on
the saved picture which is invisible in Krita."

My guess is that it's there but not very visible on the white-and-grey
transparency checkerboard, and just a bit that you wanted to erase but
didn't erase completely with the soft eraser because you couldn't see
it. If you are working on black and white pictures, it's probably best
to either change the colour of the transparency checkerboard (Settings
-> Configure Krita -> Display -> Grid Settings -> Transparency  
Checkerboard), or to add a solid bright colour layer at the bottom of
your layer stack and toggle the vibisility of that on and off for
checking. And of course toggle visibility off for export. ;)

Created attachment 127775 [details]
attachment-21683-0.html

Rebecca Breu schreef:
> https://bugs.kde.org/show_bug.cgi?id=420342
>
> Rebecca Breu<rebecca@rbreu.de>  changed:
>
>             What    |Removed                     |Added
> ----------------------------------------------------------------------------
>                   CC|                            |rebecca@rbreu.de
>
> --- Comment #6 from Rebecca Breu<rebecca@rbreu.de>  ---
> I still don't know what exactly you are doing, and I can't reproduce
> any bugs regarding transparency.
>
> "Therefor I started to change the background to 'white-transparent'."
>
> What do you mean by this? The transparency checkerboard of the canvas?
> Your layers? Your png export?
>
> "This figure should have a transparent background and had it through the
> whole procedure of making but once saved, the background is white,
> transparency gone."
>
> You should save your images as kra files and only export them to other
> file formats once you are done. If you don't export the png with "Store
> alpha channel" enabled, then (and only then) you get to pick a colour
> at the bottom of the export dialog with which your transparency is
> going to be replaced and then, yes, the transparency will be gone in
> the exported png. Even if you open that png up again in Krita.
>
> "And in some occasions a soft grey or white shade appears on
> the saved picture which is invisible in Krita."
>
> My guess is that it's there but not very visible on the white-and-grey
> transparency checkerboard, and just a bit that you wanted to erase but
> didn't erase completely with the soft eraser because you couldn't see
> it. If you are working on black and white pictures, it's probably best
> to either change the colour of the transparency checkerboard (Settings
> -> Configure Krita -> Display -> Grid Settings -> Transparency
> Checkerboard), or to add a solid bright colour layer at the bottom of
> your layer stack and toggle the vibisility of that on and off for
> checking. And of course toggle visibility off for export. ;)
>
Thanks very much, Rebecca, I never used kra-format before because I did 
not understand the necessity of it since I could save in png directly. 
The problem with 'native' formats is that one cannot publish in them, 
except for the native Photoshop format psd, which is even known to 
vector programs. I will experiment in that direction, saving in kra 
exporting in png.

You didn't understand my silly "Therefore I started to change the 
background to 'white transparent'."

I started using Krita seriously in MacOS. There is given a very 
'playful' way of changing the background colour and transparency by way 
of choosing the colour of a 'colouring pencil'. So when the chequered 
background was to dark for me to see some edge details in the b/w 
drawing, I chose white in the background and set the transparency to 
50%, making sure that I could set the transparency back tot 100% 
afterwards. In some cases that did not work as perfectly as I had hoped 
for.

I will follow your advice for which I am very thankful and I 'll see 
what happens.

Have a very nice day and keep healthy.

Best regards,

Rudolf Kahl

Created attachment 127776 [details]
Krita.png

I guess I'll close this report then, since it seems things got resolved...

Yes indeed, thank you all very much.

Have a nice weekend and keep healthy.

Rudolf

Op 24-04-2020 om 13:45 schreef wolthera:
> https://bugs.kde.org/show_bug.cgi?id=420342
>
> wolthera <griffinvalley@gmail.com> changed:
>
>             What    |Removed                     |Added
> ----------------------------------------------------------------------------
>                   CC|                            |griffinvalley@gmail.com
>               Status|REPORTED                    |RESOLVED
>           Resolution|---                         |NOT A BUG
>
> --- Comment #9 from wolthera <griffinvalley@gmail.com> ---
> I guess I'll close this report then, since it seems things got resolved...
>