使用js画图之圆、弧、扇形

//圆形/椭圆
//dot 圆点
//r 半径
//pressionRatio 垂直压缩比
function drawCircle(dot, r, pressionRatio, data){
    var pstart = [dot[0]+r, dot[1]]; //起点
    var pre = pstart;
    for(var i=0; i < 360; i+=5){
        rad = iMath.PI/180; //计算弧度
        //rMath.cos(rad) 弧线的终点相对dot的水平偏移
        //rMath.sin(rad) 弧线的终点相对dot的垂直偏移
        //pressionRatio 垂直压缩比例
        var cur = [rMath.cos(rad)+dot[0], pressionRatiorMath.sin(rad)+dot[1]];
        drawLine(pre,cur);
        pre = cur; //保存当前点的坐标
    }
    drawLine(pre,pstart);//使闭合
    //描圆点
    drawPoint({
        pw:2,ph:2,color:'DarkRed',point:dot
    });
}

//画弧
//dot 圆点
//r 半径
//angle 圆心角
//angleOfSlope 与x轴的夹角
//pop 是否弹出
//title 标签
function drawArc(dot, r, angle, angleOfSlope, pop, title){
    var newDot = [dot[0], dot[1]];
    var a = (angleOfSlope+angle/2)Math.PI/180;
    if(pop){ //计算圆心的新坐标
        newDot[0] = dot[0]+10Math.cos(a);
        newDot[1] = dot[1]+10Math.sin(a);
    }
    if(!angleOfSlope){
        angleOfSlope = 0;
    }
    var aos = angleOfSlopeMath.PI/180;
    var aos2 = (angleOfSlope+angle)Math.PI/180;
    var pstart = [newDot[0]+rMath.cos(aos), newDot[1]+rMath.sin(aos)]; //弧线的起点
    var pend = [newDot[0]+rMath.cos(aos2), newDot[1]+rMath.sin(aos2)]; //弧线的终点
    var pre = pstart;
    for(var i=0; i < angle; i+=2){ //在angle范围内画弧
        rad = (i+angleOfSlope)Math.PI/180;
        var cur = [rMath.cos(rad)+newDot[0], rMath.sin(rad)+newDot[1]];
        drawLine(pre,cur);
        pre = cur;
    }
}

//扇形
//dot 圆点
//r 半径
//angle 圆心角
//angleOfSlope 与x轴的夹角，确定扇形的方向
//pop 是否弹出，即是否偏离圆心
//title 标签
function drawSector(dot, r, angle, angleOfSlope, pop, title){
    var newDot = [dot[0], dot[1]];
    var a = (angleOfSlope+angle/2)Math.PI/180;
    if(pop){ //计算圆心的新坐标
        newDot[0] = dot[0]+10Math.cos(a);
        newDot[1] = dot[1]+10Math.sin(a);
    }
    if(!angleOfSlope){
        angleOfSlope = 0;
    }
    var aos = angleOfSlopeMath.PI/180;
    var aos2 = (angleOfSlope+angle)Math.PI/180;
    var pstart = [newDot[0]+rMath.cos(aos), newDot[1]+rMath.sin(aos)]; //弧线的起点
    var pend = [newDot[0]+rMath.cos(aos2), newDot[1]+rMath.sin(aos2)]; //弧线的终点
    drawLine(newDot,pstart); //连接圆心与起点
    var pre = pstart;
    for(var i=0; i < angle; i+=2){ //在angle范围内画弧
        rad = (i+angleOfSlope)Math.PI/180;
        var cur = [rMath.cos(rad)+newDot[0], rMath.sin(rad)+newDot[1]];
        drawLine(pre,cur);
        pre = cur;
    }
    drawPolyline([pre, pend, newDot]); //使闭合
    //描圆心
    drawPoint({
        pw:2,ph:2,color:'DarkRed',point:dot
    });
    //标签
    if(title){
        document.write("<span style='height: 24px; line-height: 24px; width: 80px; text-align: center; color: RED; position: absolute; left:"+(newDot[0]+r(2/4)Math.cos(a)-40)+"px; : "+(newDot[1]+r(2/4)Math.sin(a)-12)+"'>"+title+"</span>");
    }
}