JavaScript 八卦
【摘要】
<html>
<head>
<meta charset="utf8" />
<title>伏羲八卦</titl...
<html>
<head>
<meta charset="utf8" />
<title>伏羲八卦</title>
<style type="text/css">
#canvas {
background-color:yellow;
}
</style>
</head>
<body>
<canvas id="canvas" width="950" height="950">This browser does not support canvas tag</canvas>
<script type="text/javascript">
var c = document.getElementById("canvas");
var ctx = c.getContext("2d");
//太极中心点X坐标
var centerX = c.width / 2;
//太极中心点Y坐标
var centerY = c.height / 2;
//阴阳鱼(左阳右阴)形环转相抱的太极图的半径,大圈通神
var radius = 200;
//鱼头半径,中圈通气
var fishHeadRadius = radius / 2;
//鱼眼半径,小圈养精
var fisheyeRadius = radius / 6;
//当前弧度数(从0点钟方向为起始,顺时针方向为正,初始图像为左阳右阴)
var radian = 0;
//2 * Math.PI弧度切割的总份数
var radianCount = 720;
//2 * Math.PI长度,避免重复计算
var doublePI = Math.PI * 2;
var halfPI = Math.PI * 0.5;
//弧度步长
var radianStep = doublePI / radianCount;
//八卦间隔弧度
var eightCombinationRadiusStep = doublePI / 8;
//八卦间隔弧度的一半
var eightCombinationRadiusHalfStep = doublePI / 16;
var sinEightCombinationRadiusHalfStep = Math.sin(eightCombinationRadiusHalfStep);
var cosEightCombinationRadiusHalfStep = Math.cos(eightCombinationRadiusHalfStep);
//八卦内径
var eightCombinationInnerDiameter = radius + 0;
//八卦的正八边形的外切圆半径
var eightCombinationOutsideDiameter = eightCombinationInnerDiameter + 150;
//八卦的正八边形边框线宽
var eightCombinationRegularOctagonLineWidth = 15;
//八卦内径到正八边形的最短距离
var eightCombinationInnerDiameterToRegularOctagonDistance = (eightCombinationOutsideDiameter - eightCombinationRegularOctagonLineWidth / 2) * cosEightCombinationRadiusHalfStep - eightCombinationInnerDiameter;
//八卦线断开的间隔
var eightCombinationLineBreakLength = 15;
//八卦线宽
var eightCombinationLineWidth = eightCombinationInnerDiameterToRegularOctagonDistance / 7;
//八卦线两端与圆心连成的三角形在圆心处的弧度的一半
var eightCombinationLineHalfTriangleRadius = new Float32Array(3);
//八卦线两端到圆心的距离
var eightCombinationLineEndRadius = new Float32Array(3);
//八卦线条类型(外0x04,中0x02,内0x01; 1表示完整,0表示中间断开)
//var eightCombinationLineTypes = new Uint8Array([111,110,010,100,000,001,101,011]);
var eightCombinationLineTypes = new Uint8Array([7,6,2,4,0,1,5,3]);
//初始化八卦线数据
function initEightCombinationLine() {
//八卦线长(二分之一的外框长)
var eightCombinationLineLength = eightCombinationOutsideDiameter * sinEightCombinationRadiusHalfStep;
//内径到八卦线,再到正八边形的距离比例
var distanceRates = [1.5, 3.5, 5.5];
for(var i=0; i<3; i++) {
var eightCombinationLineCenterRadius = eightCombinationInnerDiameter + eightCombinationLineWidth * distanceRates[i];
eightCombinationLineHalfTriangleRadius[i] = Math.atan(eightCombinationLineLength / 2 / eightCombinationLineCenterRadius);
eightCombinationLineEndRadius[i] = eightCombinationLineCenterRadius / Math.cos(eightCombinationLineHalfTriangleRadius[i]);
}
}
//辅助线宽
var auxiliaryLineWidth = 1;
//八卦字体
var eightCombinationFont = "bold 22pt 'Microsoft YaHei',SimHei,FangSong,KaiTi,YouYuan blue";
//八卦字体颜色
var eightCombinationFontColor = "black";
//八卦方位文字的半径
var eightCombinationDirectionTextRadius = eightCombinationOutsideDiameter + 20;
//八卦文字的半径
var eightCombinationTextRadius = eightCombinationDirectionTextRadius + 40;
//八卦宫号
var eightCombinationNumRadius = eightCombinationTextRadius + 40;
//八卦方向文字
var eightCombinationDirectionTexts = ["南","西南","西","西北","北","东北","正","东南",];
//八卦文字
var eightCombinationTexts = ["乾(天)","巽xun(风)","坎(水)","艮gen(山)","坤(地)","震(雷)","离(火)","兑(沼泽)",];
//八卦宫号
var eightCombinationNums = ["一","五","六","七","八","四","三","二","一",];
//阳鱼鱼眼X坐标
var whiteFisheyeX;
//阳鱼鱼眼Y坐标
var whiteFisheyeY;
//阴鱼鱼眼X坐标
var blackFisheyeX;
//阴鱼鱼眼Y坐标
var blackFisheyeY;
//画弧
function fillArc(cx, cy, r, startRadian, endRadian, color) {
ctx.fillStyle = color;
ctx.beginPath();
ctx.arc(cx, cy, r, startRadian, endRadian);
ctx.fill();
}
//描圆
function strokeCircle(cx, cy, r, color, lineWidth) {
ctx.fillStyle = color;
ctx.lineWidth = lineWidth;
ctx.beginPath();
ctx.arc(cx, cy, r, 0, doublePI);
ctx.stroke();
}
//绘制经过圆心的直径
function strokeCircleDiameter(cx, cy, r, rad, color, lineWidth) {
ctx.strokeStyle = color;
ctx.lineWidth = lineWidth
var sinRad = Math.sin(rad);
var cosRad = Math.cos(rad);
ctx.beginPath();
ctx.moveTo(cx + r * sinRad, cy - r * cosRad);
ctx.lineTo(cx - r * sinRad, cy + r * cosRad)
ctx.stroke();
}
//在圆上绘制文字
function fillCircleText(cx, cy, r, rad, color, font, text) {
ctx.fillStyle = color;
ctx.font = font;
ctx.textAlign = "center";
ctx.fillText(text, cx + r * Math.sin(rad), cy - r * Math.cos(rad));
}
//绘制八卦的某一条线
function strokeEightCombination(cx, cy, r, rad, halfTriangleRad, color, lineWidth, isBreak, breakLength) {
ctx.strokeStyle = color;
ctx.lineWidth = lineWidth;
var rad1 = rad - halfTriangleRad;
var rad2 = rad + halfTriangleRad;
var x1 = cx + r * Math.sin(rad1);
var y1 = cy - r * Math.cos(rad1);
var x2 = cx + r * Math.sin(rad2);
var y2 = cy - r * Math.cos(rad2);
ctx.beginPath();
ctx.moveTo(x1, y1);
if(isBreak !== undefined && isBreak === true && breakLength !== undefined && breakLength > 0) {
//这里不能用"向量夹角公式": con(@) = b*c/(|b|*|c|)来求夹角,因为同一个cos值有两个角与之对应
//因此这里要用相似三角形公式
var midX = (x1 + x2) / 2;
var midY = (y1 + y2) / 2;
var dx = x2 - x1;
var dy = y2 - y1;
var len = Math.sqrt(Math.pow(dx, 2) + Math.pow(dy, 2));
var halfBreakPercentage = breakLength / len / 2;
var halfBreakX = dx * halfBreakPercentage;
var halfBreakY = dy * halfBreakPercentage;
var midX1 = midX - halfBreakX;
var midY1 = midY - halfBreakY;
var midX2 = midX + halfBreakX;
var midY2 = midY + halfBreakY;
ctx.lineTo(midX1, midY1);
ctx.moveTo(midX2, midY2);
}
ctx.lineTo(x2, y2);
ctx.stroke();
}
//更新
function update() {
//radian = 0;
radian += radianStep;
if(radian >= doublePI) {
radian = 0;
}
whiteFisheyeX = centerX + fishHeadRadius * Math.sin(radian);
whiteFisheyeY = centerY - fishHeadRadius * Math.cos(radian);
blackFisheyeX = centerX - fishHeadRadius * Math.sin(radian);
blackFisheyeY = centerY + fishHeadRadius * Math.cos(radian);
}
//渲染
function render() {
ctx.clearRect(0, 0, c.width, c.height);
var rad;
//八卦外边框
ctx.lineWidth = eightCombinationRegularOctagonLineWidth;
ctx.fillStyle = "black";
ctx.beginPath();
rad = radian - eightCombinationRadiusHalfStep;
for(var i=0; i < 8; i++, rad += eightCombinationRadiusStep) {
if(i == 0) {
ctx.moveTo(centerX + eightCombinationOutsideDiameter * Math.sin(rad), centerY - eightCombinationOutsideDiameter * Math.cos(rad));
} else {
ctx.lineTo(centerX + eightCombinationOutsideDiameter * Math.sin(rad), centerY - eightCombinationOutsideDiameter * Math.cos(rad));
}
}
ctx.closePath();
ctx.stroke();
//八卦分隔线
rad = radian - eightCombinationRadiusHalfStep;
for(var i = 0; i < 4; i++, rad += eightCombinationRadiusStep) {
strokeCircleDiameter(centerX, centerY, eightCombinationOutsideDiameter, rad, "black", auxiliaryLineWidth);
}
//八卦内环
//strokeCircle(centerX, centerY, eightCombinationInnerDiameter, auxiliaryLineWidth, "black");
//八卦外环
//strokeCircle(centerX, centerY, eightCombinationOutsideDiameter, auxiliaryLineWidth, "black");
//阳鱼
fillArc(centerX, centerY, radius, halfPI + radian, Math.PI + halfPI + radian, "white");
//阴鱼
fillArc(centerX, centerY, radius, -1 * halfPI + radian, halfPI + radian, "black");
//阳鱼头
fillArc(whiteFisheyeX, whiteFisheyeY, fishHeadRadius, 0, doublePI, "white");
//阴鱼头
fillArc(blackFisheyeX, blackFisheyeY, fishHeadRadius, 0, doublePI, "black");
//阳鱼眼
fillArc(blackFisheyeX, blackFisheyeY, fisheyeRadius, 0, doublePI, "white");
//阴鱼眼
fillArc(whiteFisheyeX, whiteFisheyeY, fisheyeRadius, 0, doublePI, "black");
//八卦
rad = radian;
for(var i=0; i < 8; i++, rad += eightCombinationRadiusStep) {
for(var j=0; j<3; j++) {
var isBreak = (eightCombinationLineTypes[i] & (1 << j)) === 0;
strokeEightCombination(centerX, centerY, eightCombinationLineEndRadius[j], rad, eightCombinationLineHalfTriangleRadius[j], "black", eightCombinationLineWidth, isBreak, eightCombinationLineBreakLength);
}
}
//八卦文字
ctx.save();
//ctx.translate把画布原点平移到(x,y)
ctx.translate(centerX, centerY);
//注意: 旋转的弧度是"画布"从要绘制的目标点旋转到原来的点的弧度,也可以说是原来的点旋转到目标点的相反数.
ctx.rotate(radian - Math.PI);
for(var i=0; i < 8; i++, ctx.rotate(eightCombinationRadiusStep)) {
fillCircleText(0, 0, eightCombinationTextRadius, Math.PI, eightCombinationFontColor, eightCombinationFont, eightCombinationTexts[i]);
fillCircleText(0, 0, eightCombinationDirectionTextRadius, Math.PI, eightCombinationFontColor, eightCombinationFont, eightCombinationDirectionTexts[i]);
fillCircleText(0, 0, eightCombinationNumRadius, Math.PI, eightCombinationFontColor, eightCombinationFont, eightCombinationNums[i]);
}
ctx.restore();
}
function loop() {
update();
render();
window.requestAnimationFrame(loop);
}
function init() {
initEightCombinationLine();
loop();
}
init();
</script>
</body>
</html>
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文章来源: blog.csdn.net，作者：福州-司马懿，版权归原作者所有，如需转载，请联系作者。
原文链接：blog.csdn.net/chy555chy/article/details/54428557
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