Glancing at Sallee’s source code, it seems to be a very thin Matlab MEX wrapper around libjpeg, which is a popular C library to access JPEG files.
It should be pretty easy to write a Julia package to call libjpeg, or even just a few lines to extract the information you specifically want. We already have a Yggdrasil package (JpegTurbo_jll) to provide a compiled libjpeg binary.
In the meantime you could try one of the Python libjpeg-based libraries, which can be called from Julia via PyCall.