🚀 go-pugleaf

In <3648@phri.UUCP>, Roy Smith (roy@phri.UUCP) asks about settransfer:
>
> Does postscript automatically truncate grays to the 0-1 range...?

Good Question! [Paraphrased from Gene Rayburn, Match Game '76].
I tried the following on a NEC LC-890 SilentWriter and it seems to work.
Now we have a hypothesis.  Anyone care to disprove it by counter-example?

Yours, etc., Tony Olekshy (...!alberta!oha!tony or tony@oha.UUCP).

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72 dup scale	/x 6.5 256 div def

/shade {
    exch /a exch def /b exch a sub 1 exch div def

    { a sub b mul } settransfer

    1 1 256 { /i exch def i 1 sub x mul 0 moveto

	x 0 rlineto 0 1 rlineto x neg 0 rlineto closepath
	i 1 sub 255 div setgray fill
	} for

    0 0 moveto 6.5 0 rlineto 0 1 rlineto -6.5 0 rlineto
	closepath 1 300 div setlinewidth 0 setgray stroke

    } def % shade

gsave 1 9 translate 0.0 1.0 shade grestore
gsave 1 8 translate 0.1 0.9 shade grestore	showpage

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