The static library implementing this backend. This environment variable specifies the list of directories that may contain the configuration file. If the value of the environment variable ends with the directory separator character, then the default directories are searched after the explicitly spec ified directories. If the library was compiled with debug support enabled, this environment variable controls the debug level for this backend. E.g., a value of 128 requests all debug output to be printed.
Smaller levels reduce verbosity.
The Super Resolution mode is very slow. In this case, the driver performs buffering and you can read the image in as small an increment as you like.