From: mtklein <mtklein@chromium.org>
Date: Thu, 27 Aug 2015 19:05:56 +0000 (-0700)
Subject: Add a note about (x*y+255)/256.
X-Git-Tag: accepted/tizen/5.0/unified/20181102.025319~1075
X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=6904d1d3f1a2903fcaa4c4bd17b07d5f10af2e8e;p=platform%2Fupstream%2FlibSkiaSharp.git

Add a note about (x*y+255)/256.

BUG=skia:4117

Review URL: https://codereview.chromium.org/1312283004
---

diff --git a/src/core/Sk4px.h b/src/core/Sk4px.h
index 996847f..a7f5c9f 100644
--- a/src/core/Sk4px.h
+++ b/src/core/Sk4px.h
@@ -103,6 +103,7 @@ public:
     // May be incorrect by +-1, but is always exactly correct when *this or o is 0 or 255.
     Sk4px approxMulDiv255(const Sk16b& o) const {
         // (x*y + x) / 256 meets these criteria.  (As of course does (x*y + y) / 256 by symmetry.)
+        // FYI: (x*y + 255) / 256 also meets these criteria.  In my brief testing, it was slower.
         return this->widenLo().addNarrowHi(*this * o);
     }