I have a Qt application that has some embedded JPG files that I want to display. When I compile and run both the debug and release versions on my machine, everything works
While the most accurate answer is given already, rather than having to deploy more dlls and a folder structure, I find it much easier to just convert the images to png...no image format dlls etc. required if you use pngs.
It needs jpeg plugin to load images. If you have Qt installed they would be in %QTDIR%\plugins\imageformats.
Copy qjpeg4.dll into plugin folder on your thumb drive.
root/app.exe
root/qt.conf
root/plugins/imageformats/qjpeg4.dll
In qt.conf file set path to your plugins dir:
[Paths]
plugins=./plugins