diff options
-rw-r--r-- | include/utils/SkInterpolator.h | 11 | ||||
-rw-r--r-- | tests/InterpolatorTest.cpp | 31 |
2 files changed, 40 insertions, 2 deletions
diff --git a/include/utils/SkInterpolator.h b/include/utils/SkInterpolator.h index 9547cec8b2..e062b38f65 100644 --- a/include/utils/SkInterpolator.h +++ b/include/utils/SkInterpolator.h @@ -121,8 +121,15 @@ private: typedef SkInterpolatorBase INHERITED; }; -/** Given all the parameters are [0...1], apply the cubic specified by (0,0) - (bx,by) (cx,cy) (1,1) to value, returning the answer, also [0...1]. +/** Interpolate a cubic curve, typically to provide an ease-in ease-out transition. + All the parameters are in the range of [0...1]. + The input value is treated as the x-coordinate of the cubic. + The output value is the y-coordinate on the cubic at the x-coordinate. + + @param value The x-coordinate pinned between [0..1]. + @param bx,by,cx,cy The cubic control points where the cubic is specified + as (0,0) (bx,by) (cx,cy) (1,1) + @return the corresponding y-coordinate value, from [0..1]. */ SkScalar SkUnitCubicInterp(SkScalar value, SkScalar bx, SkScalar by, SkScalar cx, SkScalar cy); diff --git a/tests/InterpolatorTest.cpp b/tests/InterpolatorTest.cpp index 3cfd19f56b..f520ebb700 100644 --- a/tests/InterpolatorTest.cpp +++ b/tests/InterpolatorTest.cpp @@ -58,4 +58,35 @@ DEF_TEST(Interpolator, reporter) { result = inter.timeToValues(175, v); REPORTER_ASSERT(reporter, result == SkInterpolator::kNormal_Result); + for (SkScalar val = -0.1f; val <= 1.1f; val += 0.1f) { + REPORTER_ASSERT(reporter, SkScalarNearlyEqual(SkTPin(0.f, val, 1.f), + SkUnitCubicInterp(val, 1.f/3, 1.f/3, 2.f/3, 2.f/3))); + } + + // These numbers come from + // http://www.w3.org/TR/css3-transitions/#transition-timing-function_tag. + const SkScalar testTransitions[][4] = { + { 0.25f, 0.1f, 0.25f, 1 }, // ease + { 0.42f, 0, 1, 1 }, // ease in + { 0, 0, 0.58f, 1 }, // ease out + { 0.42f, 0, 0.58f, 1 }, // ease in out + }; + + const SkScalar expectedOutput[][5] = { + { 0.0947876f, 0.513367f, 0.80249f, 0.940796f, 0.994263f }, // ease + { 0.0170288f, 0.129639f, 0.31543f, 0.554749f, 0.839417f }, // ease in + { 0.160583f, 0.445251f, 0.684692f, 0.870361f, 0.982971f }, // ease out + { 0.0197144f, 0.187439f, 0.500122f, 0.812561f, 0.980286f }, // ease in out + }; + + int i = 0; + for (const SkScalar* t : testTransitions) { + int j = 0; + for (SkScalar val = 0.1f; val < 1; val += 0.2f) { + REPORTER_ASSERT(reporter, SkScalarNearlyEqual(expectedOutput[i][j++], + SkUnitCubicInterp(val, t[0], t[1], t[2], t[3]))); + } + ++i; + SkDebugf("\n"); + } } |