SYNOPSIS:
    MIX_BACKTOGREY amount

DESCRIPTION:
    Mix the backing store to the the grey value data. Amount is
    between 0.0 and 1.0 and tells how much of the backing store
    to mix into the grey values.

SEE ALSO:
    COPY_GREYTOBACK, COPY_BACKTOGREY, XCHG_GREYANDBACK, ERASE_BACK
    backingstore
