bezier.go

package gg

import (
	"math"
)

func quadraticBezier(x0, y0, x1, y1, x2, y2, ds float64, p []Point) error {
	if canUseBezierKernel {
		err := quadraticBezeirGPU(x0, y0, x1, y1, x2, y2, ds, p)
		if err == nil {
			return nil
		}
		canUseBezierKernel = false
		if ReturnErrOnGPUFailed {
			return err
		}
	}
	quadraticBezierPlatform(x0, y0, x1, y1, x2, y2, ds, p)
	return nil
}

func cubicBezier(x0, y0, x1, y1, x2, y2, x3, y3, ds float64, p []Point) error {
	if canUseBezierKernel {
		err := cubicBezeirGPU(x0, y0, x1, y1, x2, y2, x3, y3, ds, p)
		if err == nil {
			return nil
		}
		canUseBezierKernel = false
		if ReturnErrOnGPUFailed {
			return err
		}
	}
	cubicBezierPlatform(x0, y0, x1, y1, x2, y2, x3, y3, ds, p)
	return nil
}

func quadraticBezierLen(x0, y0, x1, y1, x2, y2 float64) int {
	l := math.Hypot(x1-x0, y1-y0) + math.Hypot(x2-x1, y2-y1)
	n := max(int(l+0.5), 4)
	return n
}

// QuadraticBezier computes points along a quadratic Bezier curve defined by
// (x0, y0), (x1, y1), (x2, y2).
//
// QuadraticBezier 计算由 (x0, y0)、(x1, y1)、(x2, y2) 定义的二次贝塞尔曲线上的点。
func QuadraticBezier(x0, y0, x1, y1, x2, y2 float64) ([]Point, error) {
	n := quadraticBezierLen(x0, y0, x1, y1, x2, y2)
	result := make([]Point, n)
	err := quadraticBezier(x0, y0, x1, y1, x2, y2, float64(n)-1, result)
	return result, err
}

func cubicBezierLen(x0, y0, x1, y1, x2, y2, x3, y3 float64) int {
	l := math.Hypot(x1-x0, y1-y0) + math.Hypot(x2-x1, y2-y1) + math.Hypot(x3-x2, y3-y2)
	n := max(int(l+0.5), 4)
	return n
}

// CubicBezier computes points along a cubic Bezier curve defined by
// (x0, y0), (x1, y1), (x2, y2), (x3, y3).
//
// CubicBezier 计算由 (x0, y0)、(x1, y1)、(x2, y2)、(x3, y3) 定义的三次贝塞尔曲线上的点。
func CubicBezier(x0, y0, x1, y1, x2, y2, x3, y3 float64) ([]Point, error) {
	n := cubicBezierLen(x0, y0, x1, y1, x2, y2, x3, y3)
	result := make([]Point, n)
	err := cubicBezier(x0, y0, x1, y1, x2, y2, x3, y3, float64(n)-1, result)
	return result, err
}