三阶贝塞尔曲线绘制一个近似的圆方案

来源：互联网发布：冰毒淘宝地址编辑：程序博客网时间：2024/05/17 04:23
详见：http://spencermortensen.com/articles/bezier-circle/
近似值：c = 0.551915024494f
坐标系参考图：
这里写图片描述
结果：
这里写图片描述
package com.louisgeek.louiscustomviewstudy;import android.content.Context;import android.graphics.Canvas;import android.graphics.Color;import android.graphics.Paint;import android.graphics.Path;import android.graphics.PointF;import android.util.AttributeSet;import android.view.View;/** * Created by louisgeek on 2016/10/28. */public class BezierCurveViewDrawCircle extends View {    /**     * 控制点和半径的比例 详见：http://spencermortensen.com/articles/bezier-circle/     */    private final float C = 0.551915024494f;    private  Paint mPaint;    private  int mWidth,mHeight;    private float mDisance;//控制点离数据点的距离    //顺时针    private  PointF[] mPointF_Data;    private  PointF[] mPointF_Control;    boolean drawControl=true;    float mRadius=150f;    public BezierCurveViewDrawCircle(Context context) {        this(context, null);    }    public BezierCurveViewDrawCircle(Context context, AttributeSet attrs) {        this(context, attrs,0);    }    public BezierCurveViewDrawCircle(Context context, AttributeSet attrs, int defStyleAttr) {        super(context, attrs, defStyleAttr);         init();    }    private void init() {        mPaint = new Paint();        mPaint.setColor(Color.RED);        mPaint.setStrokeWidth(4f);        mPaint.setStyle(Paint.Style.STROKE);        //        mDisance=mRadius*C;        /**         * init         */        mPointF_Data=new PointF[2*4];        for (int i = 0; i < mPointF_Data.length; i++) {            mPointF_Data[i]=new PointF();        }        mPointF_Control=new PointF[2*4];        for (int i = 0; i < mPointF_Control.length; i++) {            mPointF_Control[i]=new PointF();        }        //图解 https://code.aliyun.com/hi31588535/outside_chain/raw/master/jiangjietu.png        //屏幕坐标系的第一象限        mPointF_Data[0].set(mRadius,0);//点P3        mPointF_Data[1].set(0,mRadius);//点P0        //屏幕坐标系的第二象限        mPointF_Data[2].set(0,mRadius);//点P0        mPointF_Data[3].set(-mRadius,0);//点P9        //屏幕坐标系的第三象限        mPointF_Data[4].set(-mRadius,0);//点P9        mPointF_Data[5].set(0,-mRadius);//点P6        //屏幕坐标系的第四象限        mPointF_Data[6].set(0,-mRadius);//点P6        mPointF_Data[7].set(mRadius,0);//点P3        //屏幕坐标系的第一象限        mPointF_Control[0].set(mRadius,mDisance);//点P2        mPointF_Control[1].set(mDisance,mRadius);//点P1        //屏幕坐标系的第二象限        mPointF_Control[2].set(-mDisance,mRadius);//点P11        mPointF_Control[3].set(-mRadius,mDisance);//点P10        //屏幕坐标系的第三象限        mPointF_Control[4].set(-mRadius,-mDisance);//点P8        mPointF_Control[5].set(-mDisance,-mRadius);//点P7        //屏幕坐标系的第四象限        mPointF_Control[6].set(mDisance,-mRadius);//点P5        mPointF_Control[7].set(mRadius,-mDisance);//点P4    }    @Override    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {        super.onMeasure(widthMeasureSpec, heightMeasureSpec);        mWidth=getMeasuredWidth();        mHeight=getMeasuredHeight();    }    @Override    protected void onDraw(Canvas canvas) {        super.onDraw(canvas);        canvas.translate(mWidth/2,mHeight/2);        Path path=new Path();        //屏幕坐标系的第1象限        path.moveTo(mPointF_Data[0].x,mPointF_Data[0].y);        path.cubicTo(mPointF_Control[0].x,mPointF_Control[0].y,mPointF_Control[1].x,mPointF_Control[1].y,mPointF_Data[1].x,mPointF_Data[1].y);        //屏幕坐标系的第2象限        path.moveTo(mPointF_Data[2].x,mPointF_Data[2].y);        path.cubicTo(mPointF_Control[2].x,mPointF_Control[2].y,mPointF_Control[3].x,mPointF_Control[3].y,mPointF_Data[3].x,mPointF_Data[3].y);        //屏幕坐标系的第3象限        path.moveTo(mPointF_Data[4].x,mPointF_Data[4].y);        path.cubicTo(mPointF_Control[4].x,mPointF_Control[4].y,mPointF_Control[5].x,mPointF_Control[5].y,mPointF_Data[5].x,mPointF_Data[5].y);        //屏幕坐标系的第4象限        path.moveTo(mPointF_Data[6].x,mPointF_Data[6].y);        path.cubicTo(mPointF_Control[6].x,mPointF_Control[6].y,mPointF_Control[7].x,mPointF_Control[7].y,mPointF_Data[7].x,mPointF_Data[7].y);        canvas.drawPath(path,mPaint);        if (drawControl){            drawControlLine(canvas);        }    }    private void drawControlLine(Canvas canvas) {        mPaint.setColor(Color.GRAY);        canvas.drawLine(mPointF_Data[0].x,mPointF_Data[0].y,mPointF_Control[0].x,mPointF_Control[0].y,mPaint);        mPaint.setColor(Color.YELLOW);        canvas.drawLine(mPointF_Data[1].x,mPointF_Data[1].y,mPointF_Control[1].x,mPointF_Control[1].y,mPaint);        mPaint.setColor(Color.LTGRAY);        canvas.drawLine(mPointF_Data[2].x,mPointF_Data[2].y,mPointF_Control[2].x,mPointF_Control[2].y,mPaint);        mPaint.setColor(Color.parseColor("#5DFED0"));        canvas.drawLine(mPointF_Data[3].x,mPointF_Data[3].y,mPointF_Control[3].x,mPointF_Control[3].y,mPaint);        mPaint.setColor(Color.BLACK);        canvas.drawLine(mPointF_Data[4].x,mPointF_Data[4].y,mPointF_Control[4].x,mPointF_Control[4].y,mPaint);        mPaint.setColor(Color.BLUE);        canvas.drawLine(mPointF_Data[5].x,mPointF_Data[5].y,mPointF_Control[5].x,mPointF_Control[5].y,mPaint);        mPaint.setColor(Color.GREEN);        canvas.drawLine(mPointF_Data[6].x,mPointF_Data[6].y,mPointF_Control[6].x,mPointF_Control[6].y,mPaint);        mPaint.setColor(Color.parseColor("#FE6EEB"));        canvas.drawLine(mPointF_Data[7].x,mPointF_Data[7].y,mPointF_Control[7].x,mPointF_Control[7].y,mPaint);    }}
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