commit | b8e752198dde333e71cb1a9578cd3dfd404dd06c | [log] [tgz] |
---|---|---|

author | Lee Salzman <lsalzman@mozilla.com> | Tue Mar 14 14:52:51 2017 -0400 |

committer | Skia Commit-Bot <skia-commit-bot@chromium.org> | Wed Mar 22 19:30:30 2017 +0000 |

tree | 4189b99fd65494b29665fa72e9e94a56829a008f | |

parent | ce425510a07632f14b7b779ec3864f719cb4326b [diff] |

fix round_asymmetric_to_int to also bias bottom and right BUG=skia:6294 Change-Id: I1ee1031f1fb7cb035916e8945ce5396759955885 Reviewed-on: https://skia-review.googlesource.com/9700 Reviewed-by: Cary Clark <caryclark@google.com> Commit-Queue: Cary Clark <caryclark@google.com>

diff --git a/src/core/SkScan_Path.cpp b/src/core/SkScan_Path.cpp index 11f9c40..0415b2f 100644 --- a/src/core/SkScan_Path.cpp +++ b/src/core/SkScan_Path.cpp

@@ -562,28 +562,35 @@ } /** - * Variant of SkScalarRoundToInt, identical to SkDScalarRoundToInt except when the input fraction - * is 0.5. In this case only, round the value down. This is used to round the top and left - * of a rectangle, and corresponds to the way the scan converter treats the top and left edges. + * Variants of SkScalarRoundToInt, identical to SkDScalarRoundToInt except when the input fraction + * is 0.5. When SK_RASTERIZE_EVEN_ROUNDING is enabled, we must bias the result before rounding to + * account for potential FDot6 rounding edge-cases. + */ +#ifdef SK_RASTERIZE_EVEN_ROUNDING +static const double kRoundBias = 0.5 / SK_FDot6One; +#else +static const double kRoundBias = 0.0; +#endif + +/** + * Round the value down. This is used to round the top and left of a rectangle, + * and corresponds to the way the scan converter treats the top and left edges. */ static inline int round_down_to_int(SkScalar x) { double xx = x; - xx -= 0.5; + xx -= 0.5 + kRoundBias; return (int)ceil(xx); } -#ifdef SK_RASTERIZE_EVEN_ROUNDING /** - * Variant of SkDScalarRoundToInt that biases the input up by a half an FDot6 unit to account - * for potential FDot6 rounding in downstream FDot6 calculations. + * Round the value up. This is used to round the bottom and right of a rectangle, + * and corresponds to the way the scan converter treats the bottom and right edges. */ -static inline int round_biased_to_int(SkScalar x) { - const double bias = 0.5 / SK_FDot6One; +static inline int round_up_to_int(SkScalar x) { double xx = x; - xx += 0.5 + bias; + xx += 0.5 + kRoundBias; return (int)floor(xx); } -#endif /** * Variant of SkRect::round() that explicitly performs the rounding step (i.e. floor(x + 0.5)) @@ -604,26 +611,21 @@ * SkASSERT(0 == iright); // <--- succeeds * * - * If using SK_RASTERIZE_EVEN_ROUNDING, we need to ensure that bottom and right account for - * edges bounded by this rect being rounded to FDot6 format before being later rounded to an - * integer. For example, a value like 0.499 can be below 0.5, but round to 0.5 as FDot6, which - * would finally round to the integer 1, instead of just rounding to 0. + * If using SK_RASTERIZE_EVEN_ROUNDING, we need to ensure we account for edges bounded by this + * rect being rounded to FDot6 format before being later rounded to an integer. For example, a + * value like 0.499 can be below 0.5, but round to 0.5 as FDot6, which would finally round to + * the integer 1, instead of just rounding to 0. * * To handle this, a small bias of half an FDot6 increment is added before actually rounding to * an integer value. This simulates the rounding of SkScalarRoundToFDot6 without incurring the * range loss of converting to FDot6 format first, preserving the integer range for the SkIRect. * Thus, bottom and right are rounded in this manner (biased up), ensuring the rect is large - * enough. Top and left can round as normal since they will round (biased down) to values less - * or equal to the desired rect origin. + * enough. */ static void round_asymmetric_to_int(const SkRect& src, SkIRect* dst) { SkASSERT(dst); dst->set(round_down_to_int(src.fLeft), round_down_to_int(src.fTop), -#ifdef SK_RASTERIZE_EVEN_ROUNDING - round_biased_to_int(src.fRight), round_biased_to_int(src.fBottom)); -#else - SkDScalarRoundToInt(src.fRight), SkDScalarRoundToInt(src.fBottom)); -#endif + round_up_to_int(src.fRight), round_up_to_int(src.fBottom)); } void SkScan::FillPath(const SkPath& path, const SkRegion& origClip,