When the AIR package is compiled, it is compiled either as an 8 bit or as a 16 bit version. The information on this page describes the pixel value remapping behavior of AIR when it is compiled in 16 bit format. All 16 bit versions of AIR represent pixel values internally using numbers ranging from zero to 65535. Your image generation and display software may require that data be represented differently, so the AIR package allows pixel values to be systematically remapped when loading data from disk or saving data to disk.

Loading data from disk into a 16 bit version of AIR

When loading type 0 data (8 bit data) from disk, a 16 bit version of the AIR package will:

• multiply by 256

When loading16 bit type 1 data from disk, a 16 bit version of the AIR package will:

• make no adjustment

When loading 16 bit type 2 data from disk, a 16 bit version of the AIR package will:

• set negative values to zero
• multiply by 2

When loading 16 bit type 3 data from disk, a 16 bit version of the AIR package will:

• add 32768

Saving data from a 16 bit version of AIR

When a 16 bit version of the AIR package is compiled, a default 16 bit storage data type is selected (the storage data type is specified in the config.h file). All data (except for binary files) generated by that compiled version of the AIR package will be saved to disk using the data type that was specified at compilation. Consequently, the output data type (which is fixed for any given compilation) will not necessarily match the input data type (which can be any data type).

If a 16 bit version of AIR was compiled to generate external type 1 data

• no adjustment is made when writing data to disk

If a 16 bit version of AIR was compiled to generate external type 2 data

• values are divided by 2 before writing them to disk

If a 16 bit version of AIR was compiled to generate external type 3 data

• 32768 is subtracted from values before writing them to disk