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Re: [ft] Off by one error in freetype (or in programmer?)

From: Lawrence D'Oliveiro
Subject: Re: [ft] Off by one error in freetype (or in programmer?)
Date: Fri, 6 Apr 2018 18:55:15 +1200

On Fri, 06 Apr 2018 08:40:03 +0200 (CEST), Werner LEMBERG wrote:

> Of course there will be stair-stepping!  Just have a look into the
> additional documentation files that accompany the old TrueType
> specification (both Apple and MS versions).  You'll see rectangles
> everywhere talking about B/W rasterization.

I know, I used Macs in those days. Most of them still had only
one-bit-per-pixel screens, and people didn’t really know any better.

> A graphics system might apply filters to display such bitmaps on
> screens, but this is not covered by the TT specification.

If you are going to be filtering out frequencies above the Nyquist
limit (antialiasing), then a rectangular shape is the wrong thing to
start from, since you have already thrown away even harmonics below the

You start from a dimensionless point, i.e. an “ideally-sampled” pixel.

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