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JavaScript 八卦

JavaScript
2023-09-11 14:22:55 时间 
<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>

这里写图片描述

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