HTML5 Canvas制作雷达图实战
雷达图又叫蜘蛛网图，是一种对各项数据查看很明显的表现图，在很多游戏中，对游戏中的每个角色的分析图一般也用这种图。
下面，用HTML5的Cavas来实现雷达图。
效果
一、创建Canvas
var mW = 400;var mH = 400;var mCtx = null;var canvas = document.createElement('canvas');document.body.appendChild(canvas);canvas.height = mH;canvas.width = mW;mCtx = canvas.getContext('2d');二、制作多边形背景
var mCount = 6; //边数var mCenter = mW /2; //中心点var mRadius = mCenter - 50; //半径(减去的值用于给绘制的文本留空间)var mAngle = Math.PI * 2 / mCount; //角度var mColorPolygon = '#B8B8B8'; //多边形颜色// 绘制多边形边function drawPolygon(ctx){ ctx.save(); ctx.strokeStyle = mColorPolygon; var r = mRadius/ mCount; //单位半径 //画6个圈 for(var i = 0; i < mCount; i ++){ ctx.beginPath(); var currR = r * ( i + 1); //当前半径 //画6条边 for(var j = 0; j < mCount; j ++){ var x = mCenter + currR * Math.cos(mAngle * j); var y = mCenter + currR * Math.sin(mAngle * j); ctx.lineTo(x, y); } ctx.closePath() ctx.stroke(); } ctx.restore();}效果：
三、连接顶点线
var mColorLines = '#B8B8B8'; //顶点连线颜色//顶点连线function drawLines(ctx){ ctx.save(); ctx.beginPath(); ctx.strokeStyle = mColorLines; for(var i = 0; i < mCount; i ++){ var x = mCenter + mRadius * Math.cos(mAngle * i); var y = mCenter + mRadius * Math.sin(mAngle * i); ctx.moveTo(mCenter, mCenter); ctx.lineTo(x, y); } ctx.stroke(); ctx.restore();}效果：## 四、绘制数据文本```javascriptvar mData = [['速度', 77], ['力量', 72], ['防守', 46], ['射门', 50], ['传球', 80], ['耐力', 60]]; //数据var mColorText = '#000000';//绘制文本function drawText(ctx){ ctx.save(); var fontSize = mCenter / 12; ctx.font = fontSize + 'px Microsoft Yahei'; ctx.fillStyle = mColorText; for(var i = 0; i < mCount; i ++){ var x = mCenter + mRadius * Math.cos(mAngle * i); var y = mCenter + mRadius * Math.sin(mAngle * i); //通过不同的位置，调整文本的显示位置 if( mAngle * i >= 0 && mAngle * i <= Math.PI / 2 ){ ctx.fillText(mData[i][0], x, y + fontSize); }else if(mAngle * i > Math.PI / 2 && mAngle * i <= Math.PI){ ctx.fillText(mData[i][0], x - ctx.measureText(mData[i][0]).width, y + fontSize); }else if(mAngle * i > Math.PI && mAngle * i <= Math.PI * 3 / 2){ ctx.fillText(mData[i][0], x - ctx.measureText(mData[i][0]).width, y); }else{ ctx.fillText(mData[i][0], x, y); } } ctx.restore();}<div class="se-section-delimiter"></div>效果：
五、绘制数据覆盖区域
//绘制数据区域function drawRegion(ctx){ ctx.save(); ctx.beginPath(); for(var i = 0; i < mCount; i ++){ var x = mCenter + mRadius * Math.cos(mAngle * i) * mData[i][1] / 100; var y = mCenter + mRadius * Math.sin(mAngle * i) * mData[i][1] / 100; ctx.lineTo(x, y); } ctx.closePath(); ctx.fillStyle = 'rgba(255, 0, 0, 0.5)'; ctx.fill(); ctx.restore();}<div class="se-section-delimiter"></div>效果：
六、绘制数据点
把每个数据与线的焦点绘制出来。
//画点function drawCircle(ctx){ ctx.save(); var r = mCenter / 18; for(var i = 0; i < mCount; i ++){ var x = mCenter + mRadius * Math.cos(mAngle * i) * mData[i][1] / 100; var y = mCenter + mRadius * Math.sin(mAngle * i) * mData[i][1] / 100; ctx.beginPath(); ctx.arc(x, y, r, 0, Math.PI * 2); ctx.fillStyle = 'rgba(255, 0, 0, 0.8)'; ctx.fill(); } ctx.restore();}<div class="se-section-delimiter"></div>效果：
最终代码
<!DOCTYPE html><html lang="en"><head> <meta charset="UTF-8"> <title>Document</title> <style type="text/css"> canvas{ } </style></head><body><script type="text/javascript"> var mW = 400; var mH = 400; var mData = [['速度', 77], ['力量', 72], ['防守', 46], ['射门', 50], ['传球', 80], ['耐力', 60]]; var mCount = mData.length; //边数 var mCenter = mW /2; //中心点 var mRadius = mCenter - 50; //半径(减去的值用于给绘制的文本留空间) var mAngle = Math.PI * 2 / mCount; //角度 var mCtx = null; var mColorPolygon = '#B8B8B8'; //多边形颜色 var mColorLines = '#B8B8B8'; //顶点连线颜色 var mColorText = '#000000'; //初始化 (function(){ var canvas = document.createElement('canvas'); document.body.appendChild(canvas); canvas.height = mH; canvas.width = mW; mCtx = canvas.getContext('2d'); drawPolygon(mCtx); drawLines(mCtx); drawText(mCtx); drawRegion(mCtx); drawCircle(mCtx); })(); // 绘制多边形边 function drawPolygon(ctx){ ctx.save(); ctx.strokeStyle = mColorPolygon; var r = mRadius/ mCount; //单位半径 //画6个圈 for(var i = 0; i < mCount; i ++){ ctx.beginPath(); var currR = r * ( i + 1); //当前半径 //画6条边 for(var j = 0; j < mCount; j ++){ var x = mCenter + currR * Math.cos(mAngle * j); var y = mCenter + currR * Math.sin(mAngle * j); ctx.lineTo(x, y); } ctx.closePath() ctx.stroke(); } ctx.restore(); } //顶点连线 function drawLines(ctx){ ctx.save(); ctx.beginPath(); ctx.strokeStyle = mColorLines; for(var i = 0; i < mCount; i ++){ var x = mCenter + mRadius * Math.cos(mAngle * i); var y = mCenter + mRadius * Math.sin(mAngle * i); ctx.moveTo(mCenter, mCenter); ctx.lineTo(x, y); } ctx.stroke(); ctx.restore(); } //绘制文本 function drawText(ctx){ ctx.save(); var fontSize = mCenter / 12; ctx.font = fontSize + 'px Microsoft Yahei'; ctx.fillStyle = mColorText; for(var i = 0; i < mCount; i ++){ var x = mCenter + mRadius * Math.cos(mAngle * i); var y = mCenter + mRadius * Math.sin(mAngle * i); if( mAngle * i >= 0 && mAngle * i <= Math.PI / 2 ){ ctx.fillText(mData[i][0], x, y + fontSize); }else if(mAngle * i > Math.PI / 2 && mAngle * i <= Math.PI){ ctx.fillText(mData[i][0], x - ctx.measureText(mData[i][0]).width, y + fontSize); }else if(mAngle * i > Math.PI && mAngle * i <= Math.PI * 3 / 2){ ctx.fillText(mData[i][0], x - ctx.measureText(mData[i][0]).width, y); }else{ ctx.fillText(mData[i][0], x, y); } } ctx.restore(); } //绘制数据区域 function drawRegion(ctx){ ctx.save(); ctx.beginPath(); for(var i = 0; i < mCount; i ++){ var x = mCenter + mRadius * Math.cos(mAngle * i) * mData[i][1] / 100; var y = mCenter + mRadius * Math.sin(mAngle * i) * mData[i][1] / 100; ctx.lineTo(x, y); } ctx.closePath(); ctx.fillStyle = 'rgba(255, 0, 0, 0.5)'; ctx.fill(); ctx.restore(); } //画点 function drawCircle(ctx){ ctx.save(); var r = mCenter / 18; for(var i = 0; i < mCount; i ++){ var x = mCenter + mRadius * Math.cos(mAngle * i) * mData[i][1] / 100; var y = mCenter + mRadius * Math.sin(mAngle * i) * mData[i][1] / 100; ctx.beginPath(); ctx.arc(x, y, r, 0, Math.PI * 2); ctx.fillStyle = 'rgba(255, 0, 0, 0.8)'; ctx.fill(); } ctx.restore(); }</script></body></html>本文参与 腾讯云自媒体分享计划，分享自微信公众号。
原始发表：2017-08-05，如有侵权请联系 cloudcommunity@tencent.com 删除
评论
登录后参与评论
推荐阅读
目录