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Bug 996108 - Use even rounding for better results when converting from scalar to fdot6 r=upstream

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This commit is contained in:
Jeff Muizelaar 2014-09-02 12:15:27 -04:00
parent e7624247c7
commit 1e77370046
3 changed files with 56 additions and 0 deletions
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27
gfx/skia/trunk/src/core/SkEdge.cpp
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@ -36,11 +36,18 @@ int SkEdge::setLine(const SkPoint& p0, const SkPoint& p1, const SkIRect* clip,
SkFDot6 x0, y0, x1, y1;
{
#ifdef SK_RASTERIZE_EVEN_ROUNDING
x0 = SkScalarRoundToFDot6(p0.fX, shift);
y0 = SkScalarRoundToFDot6(p0.fY, shift);
x1 = SkScalarRoundToFDot6(p1.fX, shift);
y1 = SkScalarRoundToFDot6(p1.fY, shift);
#else
float scale = float(1 << (shift + 6));
x0 = int(p0.fX * scale);
y0 = int(p0.fY * scale);
x1 = int(p1.fX * scale);
y1 = int(p1.fY * scale);
#endif
}
int winding = 1;
@ -171,6 +178,14 @@ int SkQuadraticEdge::setQuadratic(const SkPoint pts[3], int shift)
SkFDot6 x0, y0, x1, y1, x2, y2;
{
#ifdef SK_RASTERIZE_EVEN_ROUNDING
x0 = SkScalarRoundToFDot6(pts[0].fX, shift);
y0 = SkScalarRoundToFDot6(pts[0].fY, shift);
x1 = SkScalarRoundToFDot6(pts[1].fX, shift);
y1 = SkScalarRoundToFDot6(pts[1].fY, shift);
x2 = SkScalarRoundToFDot6(pts[2].fX, shift);
y2 = SkScalarRoundToFDot6(pts[2].fY, shift);
#else
float scale = float(1 << (shift + 6));
x0 = int(pts[0].fX * scale);
y0 = int(pts[0].fY * scale);
@ -178,6 +193,7 @@ int SkQuadraticEdge::setQuadratic(const SkPoint pts[3], int shift)
y1 = int(pts[1].fY * scale);
x2 = int(pts[2].fX * scale);
y2 = int(pts[2].fY * scale);
#endif
}
int winding = 1;
@ -321,6 +337,16 @@ int SkCubicEdge::setCubic(const SkPoint pts[4], const SkIRect* clip, int shift)
SkFDot6 x0, y0, x1, y1, x2, y2, x3, y3;
{
#ifdef SK_RASTERIZE_EVEN_ROUNDING
x0 = SkScalarRoundToFDot6(pts[0].fX, shift);
y0 = SkScalarRoundToFDot6(pts[0].fY, shift);
x1 = SkScalarRoundToFDot6(pts[1].fX, shift);
y1 = SkScalarRoundToFDot6(pts[1].fY, shift);
x2 = SkScalarRoundToFDot6(pts[2].fX, shift);
y2 = SkScalarRoundToFDot6(pts[2].fY, shift);
x3 = SkScalarRoundToFDot6(pts[3].fX, shift);
y3 = SkScalarRoundToFDot6(pts[3].fY, shift);
#else
float scale = float(1 << (shift + 6));
x0 = int(pts[0].fX * scale);
y0 = int(pts[0].fY * scale);
@ -330,6 +356,7 @@ int SkCubicEdge::setCubic(const SkPoint pts[4], const SkIRect* clip, int shift)
y2 = int(pts[2].fY * scale);
x3 = int(pts[3].fX * scale);
y3 = int(pts[3].fY * scale);
#endif
}
int winding = 1;

7
gfx/skia/trunk/src/core/SkEdge.h
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@ -89,11 +89,18 @@ int SkEdge::setLine(const SkPoint& p0, const SkPoint& p1, int shift) {
SkFDot6 x0, y0, x1, y1;
{
#ifdef SK_RASTERIZE_EVEN_ROUNDING
x0 = SkScalarRoundToFDot6(p0.fX, shift);
y0 = SkScalarRoundToFDot6(p0.fY, shift);
x1 = SkScalarRoundToFDot6(p1.fX, shift);
y1 = SkScalarRoundToFDot6(p1.fY, shift);
#else
float scale = float(1 << (shift + 6));
x0 = int(p0.fX * scale);
y0 = int(p0.fY * scale);
x1 = int(p1.fX * scale);
y1 = int(p1.fY * scale);
#endif
}
int winding = 1;

22
gfx/skia/trunk/src/core/SkFDot6.h
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@ -15,6 +15,28 @@
typedef int32_t SkFDot6;
/* This uses the magic number approach suggested here:
* http://stereopsis.com/sree/fpu2006.html and used in
* _cairo_fixed_from_double. It does banker's rounding
* (i.e. round to nearest even)
*/
inline SkFDot6 SkScalarRoundToFDot6(SkScalar x, int shift = 0)
{
union {
double fDouble;
int32_t fBits[2];
} tmp;
int fractionalBits = 6 + shift;
double magic = (1LL << (52 - (fractionalBits))) * 1.5;
tmp.fDouble = SkScalarToDouble(x) + magic;
#ifdef SK_CPU_BENDIAN
return tmp.fBits[1];
#else
return tmp.fBits[0];
#endif
}
#define SK_FDot6One (64)
#define SK_FDot6Half (32)