//圓形/橢圓

//dot 圓點(diǎn)

//r 半徑

//compressionRatio 垂直壓縮比

function drawCircle(dot, r, compressionRatio, data){

    var pstart = [dot[0]+r, dot[1]]; //起點(diǎn)

    var pre = pstart; 

    for(var i=0; i < 360; i+=5){

        rad = i*Math.PI/180; //計(jì)算弧度

        //r*Math.cos(rad) 弧線的終點(diǎn)相對dot的水平偏移

        //r*Math.sin(rad) 弧線的終點(diǎn)相對dot的垂直偏移

        //compressionRatio 垂直壓縮比例

        var cur = [r*Math.cos(rad)+dot[0], compressionRatio*r*Math.sin(rad)+dot[1]];

        drawLine(pre,cur);

        pre = cur; //保存當(dāng)前點(diǎn)的坐標(biāo)

    }

    drawLine(pre,pstart);//使閉合

    //描圓點(diǎn)

    drawPoint({

        pw:2,ph:2,color:'DarkRed',point:dot

    });

}

二、弧

　　就在畫出圓的一部分，算法與圓相似

復(fù)制代碼代碼如下:

//畫弧

//dot 圓點(diǎn)

//r 半徑

//angle 圓心角

//angleOfSlope 與x軸的夾角

//pop 是否彈出

//title 標(biāo)簽

function drawArc(dot, r, angle, angleOfSlope, pop, title){

    var newDot = [dot[0], dot[1]];

    var a = (angleOfSlope+angle/2)*Math.PI/180; 

    if(pop){ //計(jì)算圓心的新坐標(biāo)

        newDot[0] = dot[0]+10*Math.cos(a);

        newDot[1] = dot[1]+10*Math.sin(a);

    }

    if(!angleOfSlope){

        angleOfSlope = 0;

    }

    var aos = angleOfSlope*Math.PI/180;

    var aos2 = (angleOfSlope+angle)*Math.PI/180;

    var pstart = [newDot[0]+r*Math.cos(aos), newDot[1]+r*Math.sin(aos)]; //弧線的起點(diǎn)

    var pend = [newDot[0]+r*Math.cos(aos2), newDot[1]+r*Math.sin(aos2)]; //弧線的終點(diǎn)

    var pre = pstart;

    for(var i=0; i < angle; i+=2){ //在angle范圍內(nèi)畫弧

        rad = (i+angleOfSlope)*Math.PI/180;

        var cur = [r*Math.cos(rad)+newDot[0], r*Math.sin(rad)+newDot[1]];

        drawLine(pre,cur);

        pre = cur;

    }

}

三、扇形

　　將弧的兩端與圓心相連

復(fù)制代碼代碼如下:

//扇形

//dot 圓點(diǎn)

//r 半徑

//angle 圓心角

//angleOfSlope 與x軸的夾角，確定扇形的方向

//pop 是否彈出，即是否偏離圓心

//title 標(biāo)簽

function drawSector(dot, r, angle, angleOfSlope, pop, title){

    var newDot = [dot[0], dot[1]];

    var a = (angleOfSlope+angle/2)*Math.PI/180; 

    if(pop){ //計(jì)算圓心的新坐標(biāo)

        newDot[0] = dot[0]+10*Math.cos(a);

        newDot[1] = dot[1]+10*Math.sin(a);

    }

    if(!angleOfSlope){

        angleOfSlope = 0;

    }

    var aos = angleOfSlope*Math.PI/180;

    var aos2 = (angleOfSlope+angle)*Math.PI/180;

    var pstart = [newDot[0]+r*Math.cos(aos), newDot[1]+r*Math.sin(aos)]; //弧線的起點(diǎn)

    var pend = [newDot[0]+r*Math.cos(aos2), newDot[1]+r*Math.sin(aos2)]; //弧線的終點(diǎn)

    drawLine(newDot,pstart); //連接圓心與起點(diǎn)

    var pre = pstart;

    for(var i=0; i < angle; i+=2){ //在angle范圍內(nèi)畫弧

        rad = (i+angleOfSlope)*Math.PI/180;

        var cur = [r*Math.cos(rad)+newDot[0], r*Math.sin(rad)+newDot[1]];

        drawLine(pre,cur);

        pre = cur;

    }

    drawPolyline([pre, pend, newDot]); //使閉合

    //描圓心

    drawPoint({

        pw:2,ph:2,color:'DarkRed',point:dot

    });

    //標(biāo)簽

    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; top: "+(newDot[1]+r*(2/4)*Math.sin(a)-12)+"'>"+title+"</span>");

    }

}