利用translate方法进行绘制螺旋图案的例子

spirograph.html

<canvas width="300" height="300" id="test"></canvas>
<script type="text/javascript">
    var canvas = document.getElementById('test');
    var ctx = canvas.getContext('2d');

    //绘制螺旋图案的函数
    function drawSpirograph(ctx,R,r,O){
        var x1 = R-O;
        var y1 = 0;
        var i = 1;
        ctx.beginPath();
        ctx.moveTo(x1,y1);
        do {
            if (i>20000) break;
            var x2 = (R+r)*Math.cos(i*Math.PI/72) - (r+O)*Math.cos(((R+r)/r)*(i*Math.PI/72))
            var y2 = (R+r)*Math.sin(i*Math.PI/72) - (r+O)*Math.sin(((R+r)/r)*(i*Math.PI/72))
            ctx.lineTo(x2,y2);
            x1 = x2;
            y1 = y2;
            i++;
        } while (x2 != R-O && y2 != 0 );
            ctx.stroke();
    }

    //调用部分代码
    ctx.fillRect(0,0,300,300);
    for (var i=0;i<3;i++) {
        for (var j=0;j<3;j++) {
            ctx.save();
            ctx.strokeStyle = "#9CFF00";
            ctx.translate(50+j*100,50+i*100);
            drawSpirograph(ctx,20*(j+2)/(j+1),-8*(i+3)/(i+1),10);
            ctx.restore();
        }
    }
</script>