Hi,
I thought I see if I can speed up PNG loading by vectorizing alpha
premultiplication, and it actually does give a nice speedup:
commit d7d592b0acb25ad8084b1d60459dd40bfd9c3356 (HEAD -> png-faster,
github/png-faster)
Author: Behdad Esfahbod <beh...@behdad.org>
Date: Tue Aug 8 21:29:25 2017 -0700
Process four pixels at a time in premultiply_data() PNG function
Load/store using memcpy(). Now this is finally faster than the
non-vectorized
code. The premultiply_data() overhead is reduced by 60%.
Numbers for:
$ ftbench -b a ~/.fonts/NotoColorEmoji.ttf
Without premultiply_data: 155 us/op
With 4-pixel vectorization: 167 us/op <---------
Without vectorization: 182 us/op
Code here:
https://github.com/behdad/freetype/commits/png-faster
The code is rather terse but readable. I can add comments. Needs some
GCC/clang checks, as well as implementing the big-endian case (or disable
it for big-endian). I couldn't find any endianness macros in FreeType.
Cheers,
--
behdad
http://behdad.org/
_______________________________________________
Freetype-devel mailing list
Freetype-devel@nongnu.org
https://lists.nongnu.org/mailman/listinfo/freetype-devel
