For openSUSE Leap 15.6 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/KDE:Frameworks5/openSUSE_Leap_15.6/KDE:Frameworks5.repo
zypper refresh
zypper install kimageformats
For openSUSE Leap 15.5 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/KDE:Frameworks5/openSUSE_Leap_15.5/KDE:Frameworks5.repo
zypper refresh
zypper install kimageformats
For Backports SLE 12 SP1 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/KDE:Frameworks5/Backports_SLE_12_SP1/KDE:Frameworks5.repo
zypper refresh
zypper install kimageformats