kde-thumbnailer-qoi is a KDE thumbnailer plugin for QOI image files (e.g. Dolphin)

• Plasma 5.x
• KDE 5.x
• Qt 5.x

• Debian/Ubuntu dependencies: build-essential extra-cmake-modules gettext libgsf-1-dev libkf5crash-dev kinit-dev libkf5globalaccel-dev libkf5kio-dev libkf5archive-dev libkf5config-dev libkdecorations2-dev libqt5x11extras5-dev qtdeclarative5-dev libkf5guiaddons-dev libkf5configwidgets-dev libkf5windowsystem-dev libkf5coreaddons-dev

• Arch dependencies: cmake extra-cmake-modules libgsf

    git clone https://github.com/tobozo/kde-thumbnailer-qoi
    cd kde-thumbnailer-qoi
    git submodule update --init --recursive
    mkdir build
    cd build
    cmake ..
    make
    sudo make install

Variant for Ubuntu:

    cmake ../ -DXDG_DATA_DIRS=/usr/local/share -DXDG_CONFIG_DIRS=/usr/local/etc/xdg -DQT_PLUGIN_PATH=/usr/local/lib/x86_64-linux-gnu/plugins -DQML2_IMPORT_PATH=/usr/local/lib/x86_64-linux-gnu/qml

Some check points if the thumbnail isn't displayed:

• image/x-qoi should be present in /etc/mime.types
• image/x-qoi should be listed in KDE file association
• The Quite OK Image Format plugin is present and enabled in Dolphin

• https://github.com/phoboslab/qoi