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fix analytic AA to work with even rounding

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Bug: skia:
Change-Id: I92b19baa06429ef2c0e9cf6928d63528f29943fe
Reviewed-on: https://skia-review.googlesource.com/42520
Reviewed-by: Yuqian Li <liyuqian@google.com>
Commit-Queue: Yuqian Li <liyuqian@google.com>
This commit is contained in:
Lee Salzman 2017-09-05 13:28:38 -04:00 committed by Skia Commit-Bot
parent 19c8726a08
commit 07c07e2dc0
1 changed files with 11 additions and 0 deletions
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11
src/core/SkAnalyticEdge.h
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@ -139,11 +139,18 @@ bool SkAnalyticEdge::setLine(const SkPoint& p0, const SkPoint& p1) {
// We must set X/Y using the same way (e.g., times 4, to FDot6, then to Fixed) as Quads/Cubics.
// Otherwise the order of the edge might be wrong due to precision limit.
const int accuracy = kDefaultAccuracy;
#ifdef SK_RASTERIZE_EVEN_ROUNDING
SkFixed x0 = SkFDot6ToFixed(SkScalarRoundToFDot6(p0.fX, accuracy)) >> accuracy;
SkFixed y0 = SnapY(SkFDot6ToFixed(SkScalarRoundToFDot6(p0.fY, accuracy)) >> accuracy);
SkFixed x1 = SkFDot6ToFixed(SkScalarRoundToFDot6(p1.fX, accuracy)) >> accuracy;
SkFixed y1 = SnapY(SkFDot6ToFixed(SkScalarRoundToFDot6(p1.fY, accuracy)) >> accuracy);
#else
const int multiplier = (1 << kDefaultAccuracy);
SkFixed x0 = SkFDot6ToFixed(SkScalarToFDot6(p0.fX * multiplier)) >> accuracy;
SkFixed y0 = SnapY(SkFDot6ToFixed(SkScalarToFDot6(p0.fY * multiplier)) >> accuracy);
SkFixed x1 = SkFDot6ToFixed(SkScalarToFDot6(p1.fX * multiplier)) >> accuracy;
SkFixed y1 = SnapY(SkFDot6ToFixed(SkScalarToFDot6(p1.fY * multiplier)) >> accuracy);
#endif
int winding = 1;
@ -186,8 +193,12 @@ struct SkBezier {
// See if left shift, covert to SkFDot6, and round has the same top and bottom y.
// If so, the edge will be empty.
static inline bool IsEmpty(SkScalar y0, SkScalar y1, int shift = 2) {
#ifdef SK_RASTERIZE_EVEN_ROUNDING
return SkScalarRoundToFDot6(y0, shift) == SkScalarRoundToFDot6(y1, shift);
#else
SkScalar scale = (1 << (shift + 6));
return SkFDot6Round(int(y0 * scale)) == SkFDot6Round(int(y1 * scale));
#endif
}
};