Created attachment 151310 [details]
Sample wallpaper for bad contrast.

Created attachment 151311 [details]
Another sample.

Created attachment 151312 [details]
The worst one.

Heh yeah this happens as well with light-colored wallpapers when using a light color scheme.

Probably when you're using a dark color scheme, we should apply a small amount of lightening to wallpaper-derived accent colors that are calculated to be too dark, and darken light ones when using a light color scheme.

This doesn't seem to be fixable by judging the system color scheme, as one can choose Breeze Twilight, and Plasma components will still use the dark color scheme but the color scheme is still light.

Hmm, that's true.

Perhaps we could just unconditionally lighten very dark calculated colors and darken very light calculated colors. That's probably the best we can do, and beyond that, users will just need to live with poor contrast when they choose to use this combination of features.

A possibly relevant merge request was started @ https://invent.kde.org/plasma/plasma-desktop/-/merge_requests/1095

A possibly relevant merge request was started @ https://invent.kde.org/plasma/plasma-desktop/-/merge_requests/1104

First of all I absolutely love the wallpaper based accent colour, brilliant work/idea. 

Unfortunately  I also like dark wallpapers and the dark theme, so 50% of my backgrounds lead to very poor contrast for the highlight colour. 

Would it be possible to modify the process to keep the selected hue H/saturation S of the accent colour but always increase/decrease the value V of the HSV tuple of the accent colour to be always lets say 25% higher/lower than the panel from the dark/light themes respectively. That way there should always be enough contrast.

Ciao Karsten

A possibly relevant merge request was started @ https://invent.kde.org/plasma/plasma-workspace/-/merge_requests/2046

Git commit 95766459f3c7de96c79f4fc1bb220b7e77f1140d by Nate Graham.
Committed on 25/08/2022 at 18:21.
Pushed by ngraham into branch 'master'.

Adjust wallpaper accent calculation to increase contrast and vibrancy

Right now, the calculation prefers the image's dominant color, which is
likely to be a color from the background. As a result, it often returns
a color that is very dark or muted, especially with wallpapers based on
night landscaped or space. The darkness is especially problematic when
using a dark color scheme, where it causes contrast issues. It also has
the effect of making the selection highlight on the desktop hard to see
since by definition, its color will be very similar to the most common
color in the wallpaper.

This commit adjusts the wallpaper accent color calculation as follows:

1. Consider a narrower range of lightness values acceptable; now the
   lightness has to be at least 0.4, and it can't be darker than 0.75.
   This fixes most of the contrast issues.
2. Try the wallpaper's highlight color before the dominant color. This
   tends to pick the color in the wallpaper that is most likely to draw
   the user's attention, even if it's not the most common color. It also
   tends to be a richer and brighter color compared to the dominant
   color, so the extracted accent color is more likly to be bright and
   pretty rather than dark and muted.
3. If the highlight color or dominant color isn't within the specified
   lightness range, lighten or darken it and try again. This makes the
   algorithm work harder to try to give you a color based on the
   highlight color or the dominant color and avoid falling back to the
   average color, which is highly likely to return a drab, muted color.
FIXED-IN: 5.26

M  +23   -11   desktoppackage/contents/views/Desktop.qml

https://invent.kde.org/plasma/plasma-desktop/commit/95766459f3c7de96c79f4fc1bb220b7e77f1140d

A possibly relevant merge request was started @ https://invent.kde.org/frameworks/kirigami/-/merge_requests/731

Git commit 6da378a1d764fb73bbcea7339b7ed01394642463 by Fushan Wen.
Committed on 12/09/2022 at 16:39.
Pushed by fusionfuture into branch 'master'.

imagecolors: make extracted colors follow WCAG contrast criterion

Filter the pixels by chroma, and adjust the lightness of extracted colors
to follow WCAG Non-text Contrast (dark theme) orContrast (Minimum) (light theme).

M  +65   -3    src/imagecolors.cpp
M  +5    -2    src/imagecolors.h

https://invent.kde.org/frameworks/kirigami/commit/6da378a1d764fb73bbcea7339b7ed01394642463