picture from stream

The question has probably already been asked a couple of times but i couldn't find anything with the "search" method... is it possible to read some binary data from a file and, knowing that this data is in fact a png for example, to convert it in a TImage thing? One "ugly" way to do so would be reading the wanted part as a binary stream, then save it as a temp file wich then would be loaded with the LoadPNG function... this is "ugly" and probably slow since it requires 2 hard drive access which could be time consuming if the pictures I want to load are big or numerous or both.
So i m looking for a cleanert way, the objective being to encapsulate my game data in a single binary file

Thanks in advance :)