本文实例为大家分享了canvas绘制折线图的具体代码，供大家参考，具体内容如下
<!DOCTYPE html><html lang="en"><head> <meta charset="UTF-8"> <title>Title</title> <style> canvas { border: 1px solid #ccc; } </style></head><body><canvas width="600" height="400"></canvas><script> /*1.构造函数*/ var LineChart = function (ctx) { /*获取绘图工具*/ this.ctx = ctx || document.querySelector('canvas').getContext('2d'); /*画布的大小*/ this.canvasWidth = this.ctx.canvas.width; this.canvasHeight = this.ctx.canvas.height; /*网格的大小*/ this.gridSize = 10; /*坐标系的间距*/ this.space = 20; /*坐标原点*/ this.x0 = this.space; this.y0 = this.canvasHeight - this.space; /*箭头的大小*/ this.arrowSize = 10; /*绘制点*/ this.dottedSize = 6; /*点的坐标 和数据有关系 数据可视化*/ } /*2.行为方法*/ LineChart.prototype.init = function (data) { this.drawGrid(); this.drawAxis(); this.drawDotted(data); }; /*绘制网格*/ LineChart.prototype.drawGrid = function () { /*x方向的线*/ var xLineTotal = Math.floor(this.canvasHeight / this.gridSize); this.ctx.strokeStyle = '#eee'; for (var i = 0; i <= xLineTotal; i++) { this.ctx.beginPath(); this.ctx.moveTo(0, i * this.gridSize - 0.5); this.ctx.lineTo(this.canvasWidth, i * this.gridSize - 0.5); this.ctx.stroke(); } /*y方向的线*/ var yLineTotal = Math.floor(this.canvasWidth / this.gridSize); for (var i = 0; i <= yLineTotal; i++) { this.ctx.beginPath(); this.ctx.moveTo(i * this.gridSize - 0.5, 0); this.ctx.lineTo(i * this.gridSize - 0.5, this.canvasHeight); this.ctx.stroke(); } }; /*绘制坐标系*/ LineChart.prototype.drawAxis = function () { /*X轴*/ this.ctx.beginPath(); this.ctx.strokeStyle = '#000'; this.ctx.moveTo(this.x0, this.y0); this.ctx.lineTo(this.canvasWidth - this.space, this.y0); this.ctx.lineTo(this.canvasWidth - this.space - this.arrowSize, this.y0 + this.arrowSize / 2); this.ctx.lineTo(this.canvasWidth - this.space - this.arrowSize, this.y0 - this.arrowSize / 2); this.ctx.lineTo(this.canvasWidth - this.space, this.y0); this.ctx.stroke(); this.ctx.fill(); /*Y轴*/ this.ctx.beginPath(); this.ctx.strokeStyle = '#000'; this.ctx.moveTo(this.x0, this.y0); this.ctx.lineTo(this.space, this.space); this.ctx.lineTo(this.space + this.arrowSize / 2, this.space + this.arrowSize); this.ctx.lineTo(this.space - this.arrowSize / 2, this.space + this.arrowSize); this.ctx.lineTo(this.space, this.space); this.ctx.stroke(); this.ctx.fill(); }; /*绘制所有点*/ LineChart.prototype.drawDotted = function (data) { /*1.数据的坐标 需要转换 canvas坐标*/ /*2.再进行点的绘制*/ /*3.把线连起来*/ var that = this; /*记录当前坐标*/ var prevCanvasX = 0; var prevCanvasY = 0; data.forEach(function (item, i) { /* x = 原点的坐标 + 数据的坐标 */ /* y = 原点的坐标 - 数据的坐标 */ var canvasX = that.x0 + item.x; var canvasY = that.y0 - item.y; /*绘制点*/ that.ctx.beginPath(); that.ctx.moveTo(canvasX - that.dottedSize / 2, canvasY - that.dottedSize / 2); that.ctx.lineTo(canvasX + that.dottedSize / 2, canvasY - that.dottedSize / 2); that.ctx.lineTo(canvasX + that.dottedSize / 2, canvasY + that.dottedSize / 2); that.ctx.lineTo(canvasX - that.dottedSize / 2, canvasY + that.dottedSize / 2); that.ctx.closePath(); that.ctx.fill(); /*点的连线*/ /*当时第一个点的时候 起点是 x0 y0*/ /*当时不是第一个点的时候 起点是 上一个点*/ if(i == 0){ that.ctx.beginPath(); that.ctx.moveTo(that.x0,that.y0); that.ctx.lineTo(canvasX,canvasY); that.ctx.stroke(); }else{ /*上一个点*/ that.ctx.beginPath(); that.ctx.moveTo(prevCanvasX,prevCanvasY); that.ctx.lineTo(canvasX,canvasY); that.ctx.stroke(); } /*记录当前的坐标，下一次要用*/ prevCanvasX = canvasX; prevCanvasY = canvasY; }); }; /*3.初始化*/ var data = [ { x: 100, y: 120 }, { x: 200, y: 160 }, { x: 300, y: 240 }, { x: 400, y: 120 }, { x: 500, y: 80 } ]; var lineChart = new LineChart(); lineChart.init(data);</script></body></html>
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