I have cropped some .png images using Gwenview
& the reduced versions are faded with Gwenview, but fully colored with Feh. I've tried using 'convert' to create .jpg versions,
but while they're much smaller in Kbytes (good),
they're also faded when viewed with Gwenview (Feh ok).
Can anyone explain what has caused this ?
Is there a way of correcting it, eg with Imagemagick ?
On Thursday, 9 September 2021 00:25:41 BST Philip Webb wrote:
I have cropped some .png images using Gwenview
& the reduced versions are faded with Gwenview, but fully colored with
Feh.
I've tried using 'convert' to create .jpg versions,
but while they're much smaller in Kbytes (good),
they're also faded when viewed with Gwenview (Feh ok).
Can anyone explain what has caused this ?
Is there a way of correcting it, eg with Imagemagick ?
Once you have converted an original raster image into a smaller (i.e. more compressed) jpeg image you have thrown away some pixels. Post-processing can't put these missing pixels back.
I think the gwenview faded display phenomenon you describe here is unlikely to be the result of your conversion, since feh displays it without any fading. It may be caused by gwenview scaling the image to a different size, to make it fit in the gwenview window, unlike feh which will open it in its original size whether its full size dimensions fit in your PC monitor or
not. You can check the gwenview % reduction/increase shown at the bottom right hand corner and change this to 100% to see if it makes any odds.
In the gwenview settings you can select what the default 'Zoom Mode' is, if indeed this is the cause of the faded image display.
Another thing perhaps related could be the anti-aliasing gwenview applies to fit the image in the window aperture and how this interacts with the image elements and the resolution of your monitor - you should be able to check this if you change the zoom level.
https://photo.stackexchange.com/questions/24512/what-is-aliasing-and-anti-al iasing
On the same PC/monitor with the same display dimensions for an image
gwenview (with its default settings) and feh ought to produce the same
output - at least they do so here.
On Thursday, 9 September 2021 00:25:41 BST Philip Webb wrote:
I have cropped some .png images using Gwenview & the reduced versionsI think the gwenview faded display phenomenon you describe here
are faded with Gwenview, but fully colored with Feh.
I've tried using 'convert' to create .jpg versions,
but while they're much smaller in Kbytes (good),
they're also faded when viewed with Gwenview (Feh ok).
is unlikely to be the result of your conversion,
since feh displays it without any fading.
It may be caused by gwenview scaling the image to a different size,
to make it fit in the gwenview window,
unlike feh, which will open it in its original size
whether its full size dimensions fit in your PC monitor or not.
You can check the gwenview % reduction/increase shown at the bottom
right hand corner and change this to 100% to see if it makes any odds.
In the gwenview settings you can select what the default 'Zoom Mode' is,
if indeed this is the cause of the faded image display.
Another thing perhaps related could be the anti-aliasing gwenview applies
to fit the image in the window aperture and how this interacts
with the image elements and the resolution of your monitor
- you should be able to check this if you change the zoom level. https://photo.stackexchange.com/questions/24512/what-is-aliasing-and-anti-aliasing
On the same PC/monitor with the same display dimensions for an image
gwenview (with its default settings) and feh
ought to produce the same output - at least they do so here.
"... but fully *colored* with Feh" :
this is probably related to the colour gamut settings of gwenview.
In the gwenview settings, on the Advanced tab,
there are settings for "Rendering intent" and "Colour profile".
Change these and see if it makes a difference.
On Sun, 12 Sep 2021 23:14:11 -0400, Philip Webb wrote:
I've tried changing all the various settings in Gwenview configHave you tried logging is as a new user with default Gwenview config?
separately, but nothing changes.
I've tried changing all the various settings in Gwenview config
separately, but nothing changes.
I've tried changing all the various settings in Gwenview configHave you tried logging is as a new user with default Gwenview config?
separately, but nothing changes.
No : why would that be expected to help ?
It remains a puzzle. Any further comments from anyone are most welcome.
Gwenview uses color-management via media-libs/lcms, feh does not.
See "Rendering intent" and "Color profile" under "Advanced"
in Gwenview's configure dialog. HTH.
Gwenview uses color-management via media-libs/lcms, feh does not.
See "Rendering intent" and "Color profile" under "Advanced"
in Gwenview's configure dialog. HTH.
That cb relevant, but I've explored further & have some results.
When I crop a JPG image with Fotoxx or Gwenview,
then view it with Gwenview, the colors remain vivid ;
this is true whether I rename the new version in Gwenview or not.
It's only when I crop a PNG image in Gwenview
& save it in place (ie with the same name), that the colors are faded
& that's only when viewed with Gwenview, not eg with Feh.
So I can avoid the problem either by cropping only with Fotoxx
or by renaming them whenever I do it with Gwenview
or by converting PNGs to JPGs before cropping them.
The bad case does look like a Gwenview bug,
but KDE bugs tend to disappear into the ocean, if reported.
Thanks for the comments. I will try redoing the faded versions,
tho' that will mean getting them from the I/net again.
Any further suggestions re causes of the bad case are welcome.
On Tue, 14 Sep 2021 01:07:42 -0400, Philip Webb wrote:
So I can avoid the problem either by cropping only with FotoxxThe latter will result in loss of information.
or by renaming them whenever I do it with Gwenview
or by converting PNGs to JPGs before cropping them.
The bad case does look like a Gwenview bug,It sounds like the images are fine, just that Gwenview is displaying
but KDE bugs tend to disappear into the ocean, if reported.
with the wrong colour information. The question then becomes
does Gwenview save the colour information in the image file or separately.
If you do have another user set up,
you could try cropping and saving as one user and viewing as the other.
If the second user sees the image as it should be,
it is the latter and you can locate and remove that information.
It does seems to be a bug, and one that has been around for some years: https://forum.kde.org/viewtopic.php?f=66&t=139430
And then Adam said, "What's a headache ? "
I believe I've found a solution as above.
I'd say you have found a workaround rather than a solution, but if it
works for you...
It sounds like the images are fine, just that Gwenview is displaying
with the wrong colour information. The question then becomes
does Gwenview save the colour information in the image file or
separately. If you do have another user set up,
you could try cropping and saving as one user and viewing as the
other. If the second user sees the image as it should be,
it is the latter and you can locate and remove that information.
That's all very complex & far more work than I care to spend time on.
I believe I've found a solution as above.
| Sysop: | Keyop |
|---|---|
| Location: | Huddersfield, West Yorkshire, UK |
| Users: | 296 |
| Nodes: | 16 (2 / 14) |
| Uptime: | 23:29:06 |
| Calls: | 6,646 |
| Calls today: | 1 |
| Files: | 12,191 |
| Messages: | 5,327,626 |