I was wondering, what is the best way to go about scaling an image in SDL using C++. I want to use this in order to make a health and armor bar graphically. I'm not to sure how to do it, many thanks for any help!

If you are using SDL2, just use a bigger rectangle for dstrect. The texture will stretch to fit the dstrect.

https://wiki.libsdl.org/SDL_RenderCopy