Hi Hans (et al),
On Wed, Jul 16, 2025 at 08:33 (+0200), Hans Hagen via ntg-context wrote:
> On 7/16/2025 1:14 AM, Max Chernoff via ntg-context wrote:
>> Hi Jim,
>> On Tue, 2025-07-15 at 10:06 -0300, Jim wrote:
>>> Might I ask you
>>> (a) To confirm that your PDF reader does, indeed, do SPR?
>>> (I.e., not just everything else on your system.)
>>> and
>> Ah, good point, I should have checked first. Using the following test
>> file:
>> \loadtypescriptfile[plex]
>> \setupbodyfont[plex-thin, sans]
>> \setupinterlinespace[1sp]
>> \define[1]\makeline{%
>> \setupbodyfont[#1pt]%
>> \dorecurse{
>> \numexpression(\textwidth / \widthofstring{l}) - 1\relax
>> }{l\hfill}%
>> \unskip%
>> \par%
>> }
>> \define\makelines{%
>> \processcommalist[2, 4, 6, 8, 10, 11, 12, 16, 24, 36, 72]\makeline%
>> }
>> \startTEXpage[width=6in]
>> \makelines
>> \startframedtext[
>> offset=0pt,
>> width=broad,
>> background=color,
>> backgroundcolor=black,
>> color=white,
>> ]
>> \makelines
>> \stopframedtext
>> \stopTEXpage
>> Chromium and Firefox (pdf.js) use subpixel rendering, while Evince,
>> Okular, MuPDF, and xpdf just use greyscale antialiasing. I usually use
>> Firefox to view PDFs, and everything else on my system uses subpixel
>> rendering, so I just assumed that the rest of the PDF viewers did as
>> well.
> all side effects of these pattents involved ... pathetic large company
> policies ... esp given how trhey benefit from open source (and we're not
> even talking stuff that can't be invented multiple times at the same place
> independently)
Given "all" (most of) the other programs on my system (and, apparently,
Max's system) cheerfully do SPR, I don't believe that there are (for the
last 5 or 20 years, anyway) any patents encumbering PDF readers.
Rather, what I discovered when this problem first really started to annoy
me, at least according to what I read on the internet (so take what I write
here with a grain of salt!), some libraries used by Linux PDF readers
(reportedly pango, cairo and/or their bastard offspring pangocairo) just
aren't able to do sub-pixel rendering to the canvas upon which the PDF
output is drawn.
Why this restriction was there in the first place (maybe patents in the
last millennium?) I don't know. Why the restriction has not been removed
is yet another thing I don't know. Yet another place where my lack of
knowledge is both broad and deep. :-)
Jim
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