ImageGear for C and C++ on Windows v19.10 - Updated
Thread Safety
User Guide > How to Work with... > Thread Safety

ImageGear and its associated components are completely thread-safe. The implementation of thread safety in ImageGear maximizes the performance of threaded applications on multi-CPU computers. Every ImageGear API function can be executed within a thread.

Five thread safety APIs are explained in detail in the Core Component API Function Reference.

In most cases, no additional API calls are required to achieve thread safety.

The global group of ART settings cannot be used in multi-threaded application. You have to use this function to associate a new local group of settings for each new thread. For more detailed information, see the example code for IG_thread_data_ID_associate(). 

Access to the same PDF document from multiple threads is not permitted, because multiple threads cannot share Adobe PDF Library data types. PDF docs created/opened in the main thread can be only used from the main thread.