Custom unary point color function. \n
* Data will be set only if the returned value is non zero.
* \verbatim func(src_value_plane0: number, src_value_plane1: number, ... , params1, param2, ..., x: number, y: number) -> dst_value_plane0: number, dst_value_plane1: number, ... [in Lua 5] \endverbatim
* In Lua, the params table is unpacked.
* Also each color plane is passed as a separate value, instead of inside an array.
* And the returned value contains only the target values to update, or nil (also no return value) to leave target intact.
* \ingroup point
Custom unary point color function. \n * Data will be set only if the returned value is non zero. * \verbatim func(src_value_plane0: number, src_value_plane1: number, ... , params1, param2, ..., x: number, y: number) -> dst_value_plane0: number, dst_value_plane1: number, ... [in Lua 5] \endverbatim * In Lua, the params table is unpacked. * Also each color plane is passed as a separate value, instead of inside an array. * And the returned value contains only the target values to update, or nil (also no return value) to leave target intact. * \ingroup point