Bug 500628

Created attachment 178775 [details]
Showing the pixel art look strange with smooth scaling thumbnail

SUMMARY
This is not really a bug, more so a feature request for the thumbnailer. I'm posting this here because "meven" told me to.  https://discuss.kde.org/t/dont-do-interpolation-in-thumbnails-when-the-image-is-small-resolution/30589 

In summary, 
- The thumbnailer uses Smooth Scaling. 
- This does not look good on pixel art.

STEPS TO REPRODUCE
1. Get some pixel art
2. View the thumbnail
3. Note the weird blurry look due to smooth scaling

OBSERVED RESULT
Blurry thumbnail for pixel art

EXPECTED RESULT
Sharp thumbnail for pixel art (not smoothed out)

SOFTWARE/OS VERSIONS

(available in the Info Center app, or by running `kinfo` in a terminal window)
Linux/KDE Plasma: Arch Linux
KDE Plasma Version: 6.3.1
KDE Frameworks Version: 6.11.0
Qt Version: 6.8.2

ADDITIONAL INFORMATION

According to this reddit commenter here: https://old.reddit.com/r/kde/comments/1ivwa2d/cant_disable_interpolation_on_the_dolphin/me9s4ja/ 

the thumbnail scaling method can be toggled via a single chosen enum. This is in dolphin/src/kitemviews/private/kpixmapmodifier.cpp line 284, changing the last argument in pixmap.scaled from Qt::SmoothTransformation to Qt::FastTransformation.

Although I am not a C++ developer I propose two possible solutions. 

1: An option is added in the settings to toggle smooth scaling or fast scaling for all thumbnail generation.

2: In the void function in the source code, check if the image resolution is larger than some height and width constant. If it is, use smooth scaling, otherwise if it is smaller then use fast scaling.

3: Do solution 2, but give the user an option to choose the height and width boundary for Smooth vs Fast scaling in thumbnail.