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40780304b8
We used to expand every bit in an 1bpp image to a 0 or 255 byte,
then map that to a float that's either 0.0f or 1.0f (or whatever's
in /DecodeArray), then multiply that by 255.0f to convert it to a
u8 and put that in the rgb channels of a Color.
Now we precompute the two possible outcomes (almost always Black
and White) and do a per-bit lookup.
Reduces time for
Build/lagom/bin/pdf --render-bench --render-repeats 20 --page 36 \
~/Downloads/Flatland.pdf
(the "decoded data cached" case) from 3.3s to 1.1s on my system.
Reduces time for
Build/lagom/bin/pdf --debugging-stats ~/Downloads/0000/0000231.pdf
(the "need to decode each page" case) from 52s to 43s on my machine.
Also makes paging through PDFs that contain a 1700x2200 pixel CCITT
or JBIG2 bitmap on each page noticeably snappier.