ref: 65ef69a85d1c0f4694a361f5a0a99bdbb4f2cd95
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 }