From a very cursory glance the caller image and blur are in /usr/share/voicecall-ui-jolla/calling/CallDialog.qml
near the bottom.
The explicitFilter
configures the blur effect of the ThemeImageWallpaper
component, and a few lines above that the background.wallpaper
and background.image
properties are responsible for showing an image at all.
Setting them to undefined
(instead of checking whether there is an avatar image) should disable the image.
One could also experiment with setting a different filter, or changing the blur parameters.
Personally I’m not tremendously interested in playing with this, however there is a little documentation on the blurring effect here:
Silica Reference Documentation - Sailfish OS
https://doc.qt.io/qt-5/qml-qtgraphicaleffects-gaussianblur.html
… but for details one will have to look into various places in the Silica and Lipstick qml files.
In fact, there are some dconf tunables for changing the blur parameters system wide:
/desktop/lipstick-jolla-home/blur_iterations
/desktop/lipstick-jolla-home/blur_deviation
/desktop/lipstick-jolla-home/blur_kernel
But when playing with them I saw only minimal changes to the effect. Also, for the calldialog the parameters are set explicitly, so those tunables won’t be used.