ref: 8499401ada316f99d5ea8ef058ca1669468e6a7a
dir: /sys/src/libmemdraw/alpha.hoc/
func f(x) {
return x-x%1
}
func pixel(dr, dg, db, da, sr, sg, sb, sa, m) {
M = 255-f((sa*m)/255)
print f((sr*m+dr*M)/255), " ", f((sg*m+dg*M)/255), " ", f((sb*m+db*M)/255), " ", f((sa*m+da*M)/255), "\n"
return 0
}