int IMG_Init(int flags);
initialization flags, OR'd together.
Returns all currently initialized flags.
This function loads dynamic libraries that SDL_image needs, and prepares them for use. This must be the first function you call in SDL_image, and if it fails you should not continue with the library.
Flags should be one or more flags from IMG_InitFlags OR'd together. It returns the flags successfully initialized, or 0 on failure.
Currently, these flags are:
More flags may be added in a future SDL_image release.
This function may need to load external shared libraries to support various codecs, which means this function can fail to initialize that support on an otherwise-reasonable system if the library isn't available; this is not just a question of exceptional circumstances like running out of memory at startup!
Note that you may call this function more than once to initialize with additional flags. The return value will reflect both new flags that successfully initialized, and also include flags that had previously been initialized as well.
As this will return previously-initialized flags, it's legal to call this with zero (no flags set). This is a safe no-op that can be used to query the current initialization state without changing it at all.
Since this returns previously-initialized flags as well as new ones, and you can call this with zero, you should not check for a zero return value to determine an error condition. Instead, you should check to make sure all the flags you require are set in the return value. If you have a game with data in a specific format, this might be a fatal error. If you're a generic image displaying app, perhaps you are fine with only having JPG and PNG support and can live without WEBP, even if you request support for everything.
Unlike other SDL satellite libraries, calls to IMG_Init do not stack; a single call to IMG_Quit() will deinitialize everything and does not have to be paired with a matching IMG_Init call. For that reason, it's considered best practices to have a single IMG_Init and IMG_Quit call in your program. While this isn't required, be aware of the risks of deviating from that behavior.
After initializing SDL_image, the app may begin to load images into SDL_Surfaces or SDL_Textures.
This function is available since SDL_image 2.0.0.