Native bindings to the APPLE_biased_fixed_point_image_formats extension.

This selector may be passed to CreateImage2D in the cl_image_format.image_channel_data_type field. It defines a biased signed 1.14 fixed point storage format, with range [-1, 3). The conversion from float to this fixed point format is defined as follows:

ushort float_to_sfixed14( float x ){
    int i = convert_int_sat_rte( x * 0x1.0p14f );         // scale [-1, 3.0) to [-16384, 3*16384), round to nearest integer
    i = add_sat( i, 0x4000 );                             // apply bias, to convert to [0, 65535) range
    return convert_ushort_sat(i);                         // clamp to destination size
}

The inverse conversion is the reverse process. The formats are currently only available on the CPU with the RGBA channel layout.