#include "bezierline.h"

BezierLine::BezierLine(QWidget *parent)
{
    this->setParent(parent);

/*
    阶数 ： 公式
    order = 2: P = (1-t)^2*P0 + 2(1-t)*t*P1 + t^2*P2
    order = 3: P = (1-t)^3*P0 + 3(1-t)^2*t*P1 + 3(1-t)*t^2*P2 + t^3*P3
    order = 4: P = (1-t)^4*P0 + 4(1-t)^3*t*P1 + 6(1-t)^2*t^2*P2 + 4(1-t)*t^3*P3 + t^4*P4
    order = 5: P = (1-t)^5*P0 + 5(1-t)^4*t*P1 + 10(1-t)^3*t^2*P2 + 10(1-t)^2*t^3*P3 + 5(1-t)*t^4*P4 + t^5*P5
    order = 6: P = (1-t)^6*P0 + 6(1-t)^5*t*P1 + 15(1-t)^4*t^2*P2 + 20(1-t)^3*t^3*P3 + 15(1-t)^2*t^4*P4 + 6(1-t)*t^5*P5 + t^6*P6

    系数 杨辉三角
    O=0:              1
    O=1:            1    1
    O=2:          1   2    1
    O=3:        1   3    3   1
    O=4:      1   4   6    4   1
    O=5:    1   5   10  10   5   1
    O=6:  1   6  15   20  15   6    1
*/
}

void BezierLine::paintEvent(QPaintEvent *event)
{
    if(event->type() != QEvent::Paint){
        qDebug() << __FILE__ << __LINE__ <<  event->type();
        return;
    }

    QPainter painter(this);

//    bezierOrder2(painter);
//    bezierOrder3(painter);
//    bezierOrder4(painter);
    bezierOrder6(painter);
}

void BezierLine::bezierOrder2(QPainter & painter)
{
    double t = 0;
    int number = 100;
    double step = 1.0 / number;

    QVector2D V1(100,100),V2(100,50),V3(150,50);

    QVector2D Q1;
    QPointF * arr;

    arr = new QPointF[number+1];

    int i = 0;
    for(i=0; i <= number; i++)
    {
        t =  i * step;
        Q1 = (1-t)*(1-t)*V1 + 2* t* (1-t) * V2+ t*t*V3;
        arr[i].setX(Q1.x());
        arr[i].setY(Q1.y());
    }

    painter.drawPolyline(arr,number);

    delete []arr;
}

void BezierLine::bezierOrder3(QPainter & painter)
{
    double t = 0;
    int number = 100;
    double step = 1.0 / number;

    QVector2D V1(100,100),V2(100,50),V3(150,50),V4(150,100);

    QVector2D Q1;
    QPointF * arr;

    arr = new QPointF[number+1];

    int i = 0;
    for(i=0; i <= number; i++)
    {
        t =  i * step;
        Q1 = (1-t)*(1-t)*(1-t)*V1 + 3* (1-t) * (1-t) * t * V2+ 3*(1-t) *t*t *V3 + t*t*t*V4;
        arr[i].setX(Q1.x());
        arr[i].setY(Q1.y());
    }

    painter.drawPolyline(arr,number);

    delete []arr;
}

void BezierLine::bezierOrder4(QPainter & painter)
{
    double t = 0;
    int number = 100;
    double step = 1.0 / number;

    QVector2D V1(100,100);
    QVector2D V2(100,50);
    QVector2D V3(150,50);
    QVector2D V4(150,100);
    QVector2D V5(125,75);

    QVector2D Q1;
    QPointF * arr;

    arr = new QPointF[number+1];

    int i = 0;
    for(i=0; i <= number; i++)
    {
        t =  i * step;
        Q1 = (1-t)*(1-t)*(1-t)*(1-t)*V1 + 4*(1-t)*(1-t)*(1-t)*t*V2+ 6*(1-t)*(1-t) *t*t *V3 + 4*(1-t)* t*t*t*V4 + t*t*t*t *V5;
        arr[i].setX(Q1.x());
        arr[i].setY(Q1.y());
    }

    painter.drawPolyline(arr,number);

    delete []arr;
}

void BezierLine::bezierOrder6(QPainter & painter)
{
    double t = 0;
    int number = 100;
    double step = 1.0 / number;

    QVector2D V1(100,100);
    QVector2D V2(100, 50);
    QVector2D V3(150, 50);
    QVector2D V4(200, 150);
    QVector2D V5(250, 50);
    QVector2D V6(300, 50);
    QVector2D V7(300, 100);

    QVector2D Q1;
    QPointF * arr;

    arr = new QPointF[number+1];

    int i = 0;
    for(i=0; i <= number; i++)
    {
        t =  i * step;
        Q1 = (1-t)*(1-t)*(1-t)*(1-t)*(1-t)*(1-t)*V1 +  \
               6*(1-t)*(1-t)*(1-t)*(1-t)*(1-t)*t*V2  + \
                  15*(1-t)*(1-t)*(1-t)*(1-t)*t*t*V3 + \
                      20*(1-t)*(1-t)*(1-t)*t*t*t*V4 + \
                          15*(1-t)*(1-t)*t*t*t*t*V5 + \
                               6*(1-t)*t*t*t*t*t*V6 + \
                                     t*t*t*t*t*t*V7;
        arr[i].setX(Q1.x());
        arr[i].setY(Q1.y());
    }

    painter.drawPolyline(arr,number);

    delete []arr;
}