diff options
| author |  Brian Osman <brianosman@google.com> | 2017-12-15 11:50:20 -0500 |
|---|---|---|
| committer |  Skia Commit-Bot <skia-commit-bot@chromium.org> | 2017-12-15 19:25:08 +0000 |
| commit | ef8dda227b55445de090cfc5c59fb633f8a1763d (patch) | |
| tree | 78ee7c2c5d7ae6d2c2e9c16a68d015185681a2e6 /include | |
| parent | 2d53d984251a753b9d0fb3adad3be09243cf5c14 (diff) | |
Increase accuracy of float -> fixed in ICC code
Add a comment to SkFixed explaining the accuracy issues of the macros.
Bug: skia:
Change-Id: Ibfecb16821fefe87822cc3acd1cf8498df10a492
Reviewed-on: https://skia-review.googlesource.com/85742
Reviewed-by: Brian Osman <brianosman@google.com>
Commit-Queue: Brian Osman <brianosman@google.com>
Diffstat (limited to 'include')
| -rw-r--r-- | include/private/SkFixed.h | 5 |
1 files changed, 5 insertions, 0 deletions
diff --git a/include/private/SkFixed.h b/include/private/SkFixed.h index adb0343bc7..05e1de49c9 100644 --- a/include/private/SkFixed.h +++ b/include/private/SkFixed.h @@ -30,6 +30,11 @@ typedef int32_t SkFixed; #define SK_FixedTanPIOver8 (0x6A0A) #define SK_FixedRoot2Over2 (0xB505) +// NOTE: SkFixedToFloat is exact. SkFloatToFixed seems to lack a rounding step. For all fixed-point +// values, this version is as accurate as possible for (fixed -> float -> fixed). Rounding reduces +// accuracy if the intermediate floats are in the range that only holds integers (adding 0.5f to an +// odd integer then snaps to nearest even). Using double for the rounding math gives maximum +// accuracy for (float -> fixed -> float), but that's usually overkill. #define SkFixedToFloat(x) ((x) * 1.52587890625e-5f) #define SkFloatToFixed(x) sk_float_saturate2int((x) * SK_Fixed1) |