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/*
* Copyright 2018 Google Inc.
*
* Use of this source code is governed by a BSD-style license that can be
* found in the LICENSE file.
*/
#include "include/core/SkCubicMap.h"
#include "include/private/base/SkFloatingPoint.h"
#include "include/private/base/SkTPin.h"
#include "src/base/SkVx.h"
#include "src/core/SkOpts.h"
#include <algorithm>
static inline bool nearly_zero(SkScalar x) {
SkASSERT(x >= 0);
return x <= 0.0000000001f;
}
static float compute_t_from_x(float A, float B, float C, float x) {
return SkOpts::cubic_solver(A, B, C, -x);
}
float SkCubicMap::computeYFromX(float x) const {
x = SkTPin(x, 0.0f, 1.0f);
if (nearly_zero(x) || nearly_zero(1 - x)) {
return x;
}
if (fType == kLine_Type) {
return x;
}
float t;
if (fType == kCubeRoot_Type) {
t = sk_float_pow(x / fCoeff[0].fX, 1.0f / 3);
} else {
t = compute_t_from_x(fCoeff[0].fX, fCoeff[1].fX, fCoeff[2].fX, x);
}
float a = fCoeff[0].fY;
float b = fCoeff[1].fY;
float c = fCoeff[2].fY;
float y = ((a * t + b) * t + c) * t;
return y;
}
static inline bool coeff_nearly_zero(float delta) {
return sk_float_abs(delta) <= 0.0000001f;
}
SkCubicMap::SkCubicMap(SkPoint p1, SkPoint p2) {
// Clamp X values only (we allow Ys outside [0..1]).
p1.fX = std::min(std::max(p1.fX, 0.0f), 1.0f);
p2.fX = std::min(std::max(p2.fX, 0.0f), 1.0f);
auto s1 = skvx::float2::Load(&p1) * 3;
auto s2 = skvx::float2::Load(&p2) * 3;
(1 + s1 - s2).store(&fCoeff[0]);
(s2 - s1 - s1).store(&fCoeff[1]);
s1.store(&fCoeff[2]);
fType = kSolver_Type;
if (SkScalarNearlyEqual(p1.fX, p1.fY) && SkScalarNearlyEqual(p2.fX, p2.fY)) {
fType = kLine_Type;
} else if (coeff_nearly_zero(fCoeff[1].fX) && coeff_nearly_zero(fCoeff[2].fX)) {
fType = kCubeRoot_Type;
}
}
SkPoint SkCubicMap::computeFromT(float t) const {
auto a = skvx::float2::Load(&fCoeff[0]);
auto b = skvx::float2::Load(&fCoeff[1]);
auto c = skvx::float2::Load(&fCoeff[2]);
SkPoint result;
(((a * t + b) * t + c) * t).store(&result);
return result;
}
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