Thus, a generic “image viewer” will not work. You need a or a workaround using conversion tools.

Are you trying to a file you found, or create a new one for a theme? What is your operating system (Windows, Android, Linux)? Is your Samsung device rooted ?

In the context of Android customization, Samsung devices utilize a specific file architecture for their Theme Store. Unlike standard Android APKs or standard image formats (PNG/JPG), Samsung packages theme data into .qmg files. Because this format is proprietary and not natively supported by standard image viewers or the Android operating system's core media framework, a specialized "QMG Viewer" is required by developers and themers to reverse-engineer or extract these assets.